santafe 2010
Tài xế O-H
The automobile as we know it was not invented in a single day by a single inventor. The history of the automobile reflects an evolution that took place worldwide. It is estimated that over 100,000 patents created the modern automobile. However, we can point to the many firsts that occurred along the way. Starting with the first theoretical plans for a motor vehicle that had been drawn up by both Leonardo da Vinci and Isaac Newton.
In 1769, the very first self-propelled road vehicle was a military tractor invented by French engineer and mechanic, Nicolas Joseph Cugnot (1725 - 1804). Cugnot used a steam engine to power his vehicle, built under his instructions at the Paris Arsenal by mechanic Brezin.
It was used by the French Army to haul artillery at a whopping speed of 2 1/2 mph on only three wheels. The vehicle had to stop every ten to fifteen minutes to build up steam power. The steam engine and boiler were separate from the rest of the vehicle and placed in the front (see engraving above). The following year (1770), Cugnot built a steam-powered tricycle that carried four passengers.
In 1771, Cugnot drove one of his road vehicles into a stone wall, making Cugnot the first person to get into a motor vehicle accident. This was the beginning of bad luck for the inventor. After one of Cugnot's patrons died and the other was exiled, the money for Cugnot's road vehicle experiments ended.
Steam engines powered cars by burning fuel that heated water in a boiler, creating steam that expanded and pushed pistons that turned the crankshaft, which then turned the wheels. During the early history of self-propelled vehicles - both road and railroad vehicles were being developed with steam engines. (Cugnot also designed two steam locomotives with engines that never worked well.) Steam engines added so much weight to a vehicle that they proved a poor design for road vehicles; however, steam engines were very successfully used in locomotives. Historians, who accept that early steam-powered road vehicles were automobiles, feel that Nicolas Cugnot was the inventor of the first automobile.
In terms of the lives of average people, there is little doubt that the automobile is the most revolutionary invention in the history of transportation since the wheel.The basic premise of the automobile is simple; choose a wheeled vehicle from the many types typically pulled by horses or oxen, add a motor and create a self-propelled, personal transportation vehicle.
The earliest ancestor of the modern automobile is probably the Fardier, a three-wheeled, steam-powered, 2.3-mph vehicle built in 1771 by Nicolas Joseph Cugnot for the French minister of war. This cumbersome machine was never put into production because it was much slower and harder to operate than a horse-drawn vehicle.
Amedee Bollee, also a Frenchman, built an improved 12-passenger steam car in 1873, but the steam engine proved impractical for a machine that was intended to challenge the speed of a horse-and-buggy. The invention of the practical automobile had to await the invention of a workable internal combustion engine.
The milestone vehicle was built in Germany in 1889 by Gottlieb Daimler and Wilhelm Maybach. Powered by a 1.5 hp, two-cylinder gasoline engine, it had a four-speed transmission and traveled at 10 mph. Another German, Karl Benz, also built a gasoline-powered car the same year. The gasoline-powered automobile, or motor car, remained largely a curiosity for the rest of the nineteenth century, with only a handful being manufactured in Europe and the United States.
The first automobile to be produced in quantity was the 1901 Curved Dash Oldsmobile, which was built in the United States by Ransom E. Olds. Modern automobile mass production, and its use of the modern industrial assembly line, is credited to Henry Ford of Detroit, Michigan, who had built his first gasoline-powered car in 1896. Ford began producing his Model T in 1908, and by 1927, when it was discontinued, over 18 million had rolled off the assembly line.
Bai 2:
About 15000 separate parts are put together to make an automobile. These parts are grouped into several systems. Each system is made up of two or more parts that work together to perform a specific job. Examples are such jobs as braking and steering.
Automotive vehicles are produces in a large variety of sizes and shapes. All have the same basic parts and systems. Today, many of these systems are controlled electronically by one or more electronic control modules (ECM). Some times an ECM is called a computer.
The basic parts and systems in an automobile are the major components. These include:
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A power train
The drive or power train carries power from the engine to the drive wheels (Fig.-18). Major power-train parts may include the clutch, transmission or transaxle, transfer case, driveshaft, and differential. Fig 1 - 9 Shows the layout of these parts for front-wheel drive, rear-wheel drive, and four-wheel drive.
Transmissions and transaxles may either manual or automatic. Automatic transmissions and transaxles automatically shift from one gear ratio to another. The driver takes no action. Manual transmissions and transaxles are shifted by hand.
To shift from one gear radio to another, the driver depresses the clutch pedal and moves the shift lever.
The clutch
Vehicles with a manual transmission or transaxle have a clutch (fig 1.19). It is between the engine and the transmission of transaxle. Before shifting, this disconnects the engine from the transmission or transaxle. Parts in these units may be damages by trying to shift while under load.
Transmissions and transaxles
Transmissions and transaxles look different. They are similar in some ways. Both are gear boxes made up of a metal case containing gears and shafts. The case is filled with oil. The transaxle provides several different forward gear ratios between the engine and the drive wheels Gear ratio is the difference in rotating speed between the engine and the wheels Other positions are reverse and neutral. Reverse allows the vehicle to move backward. Neutral disengages all gears for starting and running the engine without moving the vehicle When an engine is turning slowly, it cannot produce enough power to get the vehicle moving. The transmission gear ratios provide the necessary increase in engine torque supplied by the engine that turns the wheels to move the car.
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A steering system
so the driver can control the direction of vehicle travelThe steering system enables to driver to turn the front wheels left or right. This changes the direction of vehicle travel. Steering starts at the steering wheel in front of the driver. As it is turned, shafts and gears act on linkage, which connects to the front wheels. The wheels swing to the right or left.
The vehicle then follows the direction in which the front wheels point.A few vehicles have four-wheel steering. When the front wheels swing to one side for steering, the rear wheels also swing slightly. This can make parking easier and improve high-speed stability. Four wheel steering is controlled either mechanically or electronically. However, the rear-wheel steering movement is very small compared to that of the front wheel stering.
The engine provides the power to move the car. However, electricity powers most devices on the car The starting motor requires electricity to crank the engine. The ignition system requires electricity to deliver sparks to the cylinders. The fuel-injection system needs electricity to provide fuel. The lights, horns, radio, and air conditioner all require electricity to operate.
The car ha two sources of electricity. One is the battery. The other is the alternator in the charging system. The battery supplies electricity while the engine is off and for cranking the engine. After the engine starts, the alternator recharges the battery and supplies power for the electrical load.
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Springs, shock absorbers, and related parts between the wheels and the car body make up the suspension system spring at each wheel supports the weight of the vehicle and the load it is carrying.
The springs allow the wheels to move up and down as they meet holes and bumps in the road. As the wheels do this, the springs absorb most of the motion. Little up and down movement reaches the body.
A shock absorber at each wheel helps limit spring travel and wheel bounce. Automobile suspension systems use four types of springs. These are coil springs, leaf springs, torsion-bar springs, and air spring Some cars have electronic ride control. It automatically changes the firmness of the shock absorber to suit road conditions. Other cars have an electronic air suspension system. It is similar to electronic ride control. However, rubber bags filled with air (“air springs”) replace the metal springs.
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The engine provides the power to move the car. However, electricity powers most devices on the car The starting motor requires electricity to crank the engine. The ignition system requires electricity to deliver sparks to the cylinders. The fuel-injection system needs electricity to provide fuel. The lights, horns, radio, and air conditioner all require electricity to operate.
The car ha two sources of electricity. One is the battery. The other is the alternator in the charging system. The battery supplies electricity while the engine is off and for cranking the engine. After the engine starts, the alternator recharges the battery and supplies power for the electrical load.
Many devices and systems on the car require an electronic control system for safe and proper operation. They include electronic control of automatic transmissions and transaxles, suspension and steering, and antilock-brake and traction-control systems.
A basic control system has three parts. These are the inputs, the control unit, and the outputs. The inputs are switches and sensors. They provide information to the electronic control module (ECM). It then decides how much change to make, if any.
Then the ECM signals the output devices or actuators to take the required action.
On most engines, an electronic engine control systems (EEC) controls the ignition and fuel injection systems. In the EEC system, the electronic control module usually has a self-diagnostic capability. This means memory stores information about faults or malfunctions that have occurred and perhaps disappeared. A malfunction is an improper or incorrect operation. When recalled from the memory, this stored information helps the technician diagnose and repair the vehicle.
Bai 3:
Introduction
Have you ever opened the hood of your car and wondered what was going on in there? A car engine can look like a big confusing jumble of metal, tubes and wires to the uninitiated.
You might want to know what's going on simply out of curiosity. Or perhaps you are buying a new car, and you hear things like "3.0 liter -6" and "dual overhead cams" and "tuned port fuel injection." What does all of that mean?
If you have ever wondered about this kind of stuff, then read on -- In this article, we'll discuss the basic idea behind an engine and then go into detail about how all the pieces fit together, what can go wrong and how to increase performance.
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The BasicsThe purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is an internal combustion engine -- combustion takes place internally. Two things to note:
• There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on HEMI engines, rotary engines and two-stroke engines. Each has its own advantages and disadvantages.
• There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines.
Almost all cars today use a reciprocating internal combustion engine because this engine is:
• Relatively efficient (compared to an external combustion engine)
• Relatively inexpensive (compared to a gas turbine)
• Relatively easy to refuel (compared to an electric car)
These advantages beat any other existing technology for moving a car around.
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Combustion is Key To understand the basic idea behind how a reciprocating internal combustion engine works, it is helpful to have a good mental image of how "internal combustion" works. One good example is an old Revolutionary War cannon. You have probably seen these in movies, where the soldiers load the cannon with gun powder and a cannon ball and light it. That is internal combustion, but it is hard to imagine that having anything to do with engines.
A more relevant example might be this: Say that you took a big piece of plastic sewer pipe, maybe 3 inches in diameter and 3 feet long, and you put a cap on one end of it. Then say that you sprayed a little WD-40 into the pipe, or put in a tiny drop of gasoline. Then say that you stuffed a potato down the pipe.
I am not recommending that you do this! But say you did... What we have here is a device commonly known as a potato cannon. When you introduce a spark, you can ignite the fuel.
What is interesting, and the reason we are talking about such a device, is that a potato cannon can launch a potato about 500 feet through the air! There is a huge amount of energy in a tiny drop of gasoline
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Internal CombustionThe potato cannon uses the basic principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!
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Counting cycleThe core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.
Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing-cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles
Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are:
• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke
Displacement
The combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume. The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1,000 cubic centimeters equals a liter).
Here are some examples:
• A chainsaw might have a 40 cc engine.
• A motorcycle might have a 500 cc or a 750 cc engine.
• A sports car might have a 5.0 liter (5,000 cc) engine.
Most normal car engines fall somewhere between 1.5 liter (1,500 cc) and 4.0 liters (4,000 cc)
If you have a 4-cylinder engine and each cylinder displaces half a liter, then the entire engine is a "2.0 liter engine." If each cylinder displaces half a liter and there are six cylinders arranged in a V configuration, you have a "3.0 liter V-6."
Generally, the displacement tells you something about how much power an engine can produce. A cylinder that displaces half a liter can hold twice as much fuel/air mixture as a cylinder that displaces a quarter of a liter, and therefore you would expect about twice as much power from the larger cylinder (if everything else is equal). So a 2.0 liter engine is roughly half as powerful as a 4.0 liter engine.
You can get more displacement in an engine either by increasing the number of cylinders or by making the combustion chambers of all the cylinders bigger (or both).
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What Can Go Wrong?So you go out one morning and your engine will turn over but it won't start... What could be wrong? Now that you know how an engine works, you can understand the basic things that can keep an engine from running. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three." Based on the simple engine we have been discussing, here is a quick run-down on how these problems affect your engine:
Bad fuel mix - A bad fuel mix can occur in several ways:
You are out of gas, so the engine is getting air but no fuel.
The air intake might be clogged, so there is fuel but not enough air.
The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.
There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.
Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:
Your piston rings are worn (allowing air/fuel to leak past the piston during compression).
The intake or exhaust valves are not sealing properly, again allowing a leak during compression.
There is a hole in the cylinder.
The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.
Lack of spark - The spark might be nonexistent or weak for a number of reasons:
If your spark plug or the wire leading to it is worn out, the spark will be weak.
If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark.
If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.
Many other things can go wrong. For example:
If the battery is dead, you cannot turn over the engine to start it.
If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run.
If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run.
If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run.
If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.
In a properly running engine, all of these factors are within tolerance.
As you can see, an engine has a number of systems that help it do its job of converting fuel into motion. Most of these subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines in the following sections
○The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down,
Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams."
Valve TrainsThe valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down.
Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves, as you see in Figure 5. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams."
Ignition SystemThe ignition system produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness.
Cooling SystemThe cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.
Air intake Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor.
Starting SystemThe starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:
All of the internal friction caused by the piston rings
The compression pressure of any cylinder(s) that happens to be in the compression stroke
The energy needed to open and close valves with the camshaft
All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.
Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor.
Lubrication SystemThe lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings that allow things like the crankshaft and camshafts to rotate freely. In most cars, oil is sucked out of the oil pan by the oil pump, run through the oil filter to remove any grit, and then squirted under high pressure onto bearings and the cylinder walls. The oil then trickles down into the sump, where it is collected again and the cycle repeats.
Fuel SystemThe fuel system pumps gas from the gas tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.
In carburetion, a device called a carburetor mixes gas into air as the air flows into the engine.
In a fuel-injected engine, the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).
Exhaust SystemThe exhaust system includes the exhaust pipe and the muffler. Without a muffler, what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens the sound. The exhaust system also includes a catalytic converter.
Emission ControlThe emission control system in modern cars consists of a catalytic converter, a collection of sensors and actuators, and a computer to monitor and adjust everything. For example, the catalytic converter uses a catalyst and oxygen to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available for the catalyst to work and adjusts things if necessary.
Produce more power
Using all of this information, you can begin to see that there are lots of different ways to make an engine perform better. Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient.
Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit.
Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power.
Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder. See How Turbochargers Work for details.
Cool the incoming air - Compressing air raises its temperature. However, you would like to have the coolest air possible in the cylinder because the hotter the air is, the less it will expand when combustion takes place. Therefore, many turbocharged and supercharged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder.
Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow.
Let exhaust exit more easily - If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with two intake and two exhaust valves has four valves per cylinder, which improves performance -- when you hear a car ad tell you the car has four cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance, this can cause back-pressure, which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has "dual exhaust," the goal is to improve the flow of exhaust by having two exhaust pipes instead of one.
Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction, it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes.
Inject the fuel - Fuel injection allows very precise metering of fuel to each cylinder. This improves performance and fuel economy.
Bai 4:
Introduction the Hybrid
Have you pulled your car up to the gas pump lately and been shocked by the high price of gasoline? As the pump clicked past $20 or $30, maybe you thought about trading in that SUV for something that gets better mileage. Or maybe you're worried that your car is contributing to the greenhouse effect. Or maybe you just want to have the coolest car on the block.
The auto industry now has the technology that might answer all of these needs. It's the hybrid car, and a few manufacturers are selling their versions in the United States. You're probably aware of hybrid cars because they've been in the news a lot. In fact, most automobile manufacturers have announced plans to manufacture their own versions -- you can even expect some hybrid SUVs to hit the streets this year.
How does a hybrid automobile work? What goes on under the hood to give you 20 or 30 more miles per gallon than the standard automobile? And does it pollute less just because it gets better gas mileage? In this article, we'll help you understand how this amazing technology works. We'll show you what is going on in the Toyota and Honda hybrids, and even give you some advice about how to drive one for maximum efficiency!
What Makes it a "Hybrid"?Any vehicle is a hybrid when it combines two or more sources of power. In fact, many people have probably owned a hybrid vehicle at some point. For example, a mo-ped (a motorized pedal bike) is a type of hybrid because it combines the power of a gasoline engine with the pedal power of its rider.
Hybrid vehicles are all around us. Most of the locomotives we see pulling trains are diesel-electric hybrids. Cities like Seattle have diesel-electric buses -- these can draw electric power from overhead wires or run on diesel when they are away from the wires. Giant mining trucks are often diesel-electric hybrids.
Submarines are also hybrid vehicles -- some the engine on a hybrid is smaller and uses advanced technologies to reduce emissions and increase efficiency.
• Fuel tank - The fuel tank in a hybrid is the energy storage device for the gasoline engine. Gasoline has a much higher energy density than batteries do. For example, it takes about 1,000 pounds of batteries to store as much energy as 1 gallon (7 pounds) of gasoline.
• Electric motor - The electric motor on a hybrid car is very sophisticated. Advanced electronics allow it to act as a motor as well as a generator. For example, when it needs to, it can draw energy from the batteries to accelerate the car. But acting as a generator, it can slow the car down and return energy to the batteries.
• Generator - The generator is similar to an electric motor, but it acts only to produce electrical power. It is used mostly on series hybrids.
• Batteries - The batteries in a hybrid car are the energy storage device for the electric motor. Unlike the gasoline in the fuel tank, which can only power the gasoline engine, the electric motor on a hybrid car can put energy into the batteries as well as draw energy from them.
• Transmission - The transmission on a hybrid car performs the same basic function as the transmission on a conventional car. Some hybrids, like the Honda Insight, have conventional transmissions. Others, like the Toyota Prius, have radically different ones, which we'll talk about later.
Why Build Such a Complex Car?You might wonder why anyone would build such a complicated machine when most people are perfectly happy with their gasoline-powered cars. The reason is twofold: to reduce tailpipe emissions and to improve mileage. These goals are actually tightly interwoven.
California emissions standards dictate how much of each type of pollution a car is allowed to emit in California. The amount is usually specified in grams per mile (g/mi). For example, the low emissions vehicle (LEV) standard allows 3.4 g/mi of carbon monoxide.
The key thing here is that the amount of pollution allowed does not depend on the mileage your car gets. But a car that burns twice as much gas to go a mile will generate approximately twice as much pollution. That pollution will have to be removed by the emissions control equipment on the car. So decreasing the fuel consumption of the car is one of the surest ways to decrease emissions.
Carbon dioxide (CO2) is another type of pollution a car produces. The U.S. government does not regulate it, but scientists suspect that it contributes to global warming. Since it is not regulated, a car has no devices for removing CO2 from the exhaust, so a car that burns twice as much gas adds twice as much CO2 to the atmosphere.
Automakers in the U.S. have another strong incentive to improve mileage. They are required by law to meet Corporate Average Fuel Economy (CAFE) standards. The current standards require that the average mileage of all the new cars sold by an automaker should be 27.5 mpg (8.55 liters per 100 km). This means that if an automaker sells one hybrid car that gets 60 mpg (3.92 liters per 100 km), it can then sell four big, expensive luxury cars that only get 20 mpg (11.76 liters per 100 km)!
Evolution of the HybridThe hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while overcoming the shortcomings of an electric car.
The Problem with Gas-powered CarsTo be useful to you or me, a car must meet certain minimum requirements. The car should be able to:
• Drive at least 300 miles (482 km) between re-fueling
• Be refueled quickly and easily
• Keep up with the other traffic on the road
A gasoline car meets these requirements but produces a relatively large amount of pollution and generally gets poor gas mileage. An electric car, on the other hand, produces almost no pollution, but it can only go 50 to 100 miles (80 to 161 km) between charges. And the problem has been that it is very slow and inconvenient to recharge.
A driver's desire for quick acceleration causes our cars to be much less efficient than they could be. You may have noticed that a car with a less powerful engine gets better gas mileage than an identical car with a more powerful engine. Just look at the window stickers on new cars at a dealership for a city and highway mpg comparison.
The amazing thing is that most of what we require a car to do uses only a small percentage of its horsepower! When you are driving along the freeway at 60 mph (96.6 kph), your car engine has to provide the power to do three things:
Overcome the aerodynamic drag caused by pushing the car through the air
• Overcome all of the friction in the car's components such as the tires, transmission, axles and brakes
• Provide power for accessories like air conditioning, power steering and headlights
For most cars, doing all this requires less than 20 horsepower! So, why do you need a car with 200 horsepower? So you can "floor it," which is the only time you use all that power. The rest of the time, you use considerably less power than you have available.
Smaller Engines are More EfficientMost cars require a relatively big engine to produce enough power to accelerate the car quickly. In a small engine, however, the efficiency can be improved by using smaller, lighter parts, by reducing the number of cylinders and by operating the engine closer to its maximum load.
There are several reasons why smaller engines are more efficient than big ones:
• The big engine is heavier than the small engine, so the car uses extra energy every time it accelerates or drives up a hill.
• The pistons and other internal components are heavier, requiring more energy each time they go up and down in the cylinder.
• The displacement of the cylinders is larger, so more fuel is required by each cylinder.
• Bigger engines usually have more cylinders, and each cylinder uses fuel every time the engine fires, even if the car isn't moving.
This explains why two of the same model cars with different engines can get different mileage. If both cars are driving along the freeway at the same speed, the one with the smaller engine uses less energy. Both engines have to output the same amount of power to drive the car, but the small engine uses less power to drive itself.
Hybrid PerformanceThe key to a hybrid car is that the gasoline engine can be much smaller than the one in a conventional car and therefore more efficient. But how can this smaller engine provide the power your car needs to keep up with the more powerful cars on the road?
Let's compare a car like the Chevy Camaro, with its big V-8 engine, to our hybrid car with its small gas engine and electric motor. The engine in the Camaro has more than enough power to handle any driving situation. The engine in the hybrid car is powerful enough to move the car along on the freeway, but when it needs to get the car moving in a hurry, or go up a steep hill, it needs help. That "help" comes from the electric motor and battery -- this system steps in to provide the necessary extra power.
The gas engine on a conventional car is sized for the peak power requirement (those few times when you floor the accelerator pedal). In fact, most drivers use the peak power of their engines less than one percent of the time. The hybrid car uses a much smaller engine, one that is sized closer to the average power requirement than to the peak power.
Hybrid EfficiencyBesides a smaller, more efficient engine, today's hybrids use many other tricks to increase fuel efficiency. Some of those tricks will help any type of car get better mileage, and some only apply to a hybrid. To squeeze every last mile out of a gallon of gasoline, a hybrid car can:
• Recover energy and store it in the battery - Whenever you step on the brake pedal in your car, you are removing energy from the car. The faster a car is going, the more kinetic energy it has. The brakes of a car remove this energy and dissipate it in the form of heat. A hybrid car can capture some of this energy and store it in the battery to use later. It does this by using "regenerative braking." That is, instead of just using the brakes to stop the car, the electric motor that drives the hybrid can also slow the car. In this mode, the electric motor acts as a generator and charges the batteries while the car is slowing down.
• Sometimes shut off the engine - A hybrid car does not need to rely on the gasoline engine all of the time because it has an alternate power source -- the electric motor and batteries. So the hybrid car can sometimes turn off the gasoline engine, for example when the vehicle is stopped at a red light.
• Use advanced aerodynamics to reduce drag - When you are driving on the freeway, most of the work your engine does goes into pushing the car through the air. This force is known as aerodynamic drag. This drag force can be reduced in a variety of ways. One sure way is to reduce the frontal area of the car. Think of how a big SUV has to push a much greater area through the air than a tiny sports car.
Reducing disturbances around objects that stick out from the car or eliminating them altogether can also help to improve the aerodynamics. For example, covers over the wheel housings smooth the airflow and reduce drag. And sometimes, mirrors are replaced with small cameras.
• Use low-rolling resistance tires - The tires on most cars are optimized to give a smooth ride, minimize noise, and provide good traction in a variety of weather conditions. But they are rarely optimized for efficiency. In fact, the tires cause a surprising amount of drag while you are driving. Hybrid cars use special tires that are both stiffer and inflated to a higher pressure than conventional tires. The result is that they cause about half the drag of regular tires.
Use lightweight materials - Reducing the overall weight of a car is one easy way to increase the mileage. A lighter vehicle uses less energy each time you accelerate or drive up a hill. Composite materials like carbon fiber or lightweight metals like aluminum and magnesium can be used to reduce weight. What's Available Now?Three hybrid cars are now available in the United States -- the Honda Civic Hybrid, the Honda Insight and the Toyota Prius. We will be discussing the latter two, and although both of these cars are hybrids, they are actually quite different in character.
Coming Soon!
Over the past four years, more than 100,000 hybrids have been sold in the United States. (The Prius and the Honda Civic Hybrid account for the majority of these sales.) Even though that's not a huge percentage of the more than 17 million new cars and trucks that are sold in the U.S. each year, it's enough of an incentive to get more manufacturers on the hybrid bandwagon. Analysts suggest that the market this year, alone, could muster up the sales of the past four combined.
Below are some of the models manufacturers soon plan to integrate into the consumer market.
The Honda Insightshows the layout of the Honda Insight, which is a simplified parallel hybrid. It has an electric motor coupled to the engine at the spot where the flywheel usually goes. Honda calls this system "Integrated Motor Assist." The Insight also has a conventional five-speed manual transmission. For those of you that have trouble changing gears, or prefer an automatic transmission, the Insight CVT is now available. Prices start at $21,280.
The electric motor on the Insight helps in several ways. It can:
• Assist the gasoline engine, providing extra power while the car is accelerating or climbing a hill
• Provide some regenerative braking to capture energy during braking
• Start the engine, eliminating the need for a starter
However, the motor cannot power the car by itself; the gas engine must be running for the car to move. Insight Fuel EfficiencyBecause the Insight was designed to get the best mileage possible, Honda used all of the tricks discussed in the previous section. But the Insight relies mainly on three areas:
- It reduces the weight - Already a small car, the Insight uses a lightweight aluminum body and structure to further reduce weight. By making the car lightweight, Honda was able to use a smaller, lighter engine that could still maintain the performance level we have come to expect from our cars. The Insight weighs less than 1,900 pounds (862 kg), which is 500 pounds (227 kg) less than the lightest Honda Civic.
• It uses a small, efficient engine - The engine in the Insight, shown in Figure 7, weighs only 124 pounds (56 kg) and is a tiny, 1.0-liter three-cylinder that produces 67 horsepower at 5,700 rpm. It incorporates Honda's VTEC system and uses lean burn technology to maximize efficiency. The Insight achieves an EPA mileage rating of 61 mpg/city and 70 mpg/highway. Also, with the additional power provided by the small electric motor, this system is able to accelerate the Insight from 0 to 60 mph in about 11 seconds.
With the electric motor running, the Insight produces 73 horsepower at 5,700 rpm. If you compare that to the engine horsepower alone, it looks like the electric motor only adds 6 horsepower. But the real effectiveness of the electric motor occurs at lower engine speeds. The electric motor on the Insight is rated at 10 kilowatts (about 13 horsepower) at 3,000 rpm.
It's the peak torque numbers that really tell the story. Without the electric motor, the Insight makes its peak torque of 66 pound-feet at 4,800 rpm. With the electric motor, it makes 91 pound-feet at 2,000 rpm. So the motor adds a lot of torque to the low end of the speed range, where the engine is weaker. This is a nice compromise that allows Honda to give a very small engine the feel of a much larger one.
It uses advanced aerodynamics - The Honda Insight is designed using the classical teardrop shape: The back of the car is narrower than the front. (Note that real teardrops do not behave this way aerodynamically. The rear wheels are partially covered by bodywork to provide a smoother shape, and some parts of the underside of the car are enclosed with plastic panels. These tricks result in a drag coefficient of 0.25, which makes it one of the most aerodynamic cars on the market.
Driving the InsightThe Insight is actually not very different from a conventional car once you get behind the wheel. When you accelerate, the gas engine does most of the work. If you accelerate quickly, the electric motor kicks in to provide a little extra power.
When you are cruising along the freeway, the gas engine is doing all of the work. When you slow down by hitting the brakes or letting off the gas, the electric motor kicks in to generate a little electricity to charge the batteries. You never have to plug the Insight into an electrical outlet; the motor generates all of the power needed to charge the battery.
One interesting thing to note is that in the Insight, the manual transmission is separated from the engine and motor by the clutch. This means that if you are the type of driver who likes to put the clutch in or put the car in neutral when you slow down to a stop, you are not going to get any regenerative braking. In order to recover energy when you slow down, the car has to be in gear.
The Honda Insight price starts around $19,570, and the Toyota Prius starts around $20,510. Both cars have a gasoline engine, an electric motor and batteries, but that is where the similarities end.
The Honda Insight, which was introduced in early 2000 in the United States, is designed to get the best possible mileage. Honda used every trick in the book to make the car as efficient as it can be. The Insight is a small, lightweight two-seater with a tiny, high-efficiency gas engine.
The Toyota Prius, which came out in Japan at the end of 1997, is designed to reduce emissions in urban areas. It meets California's super ultra low emissions vehicle (SULEV) standard. It is a four-door sedan that seats five, and the powertrain is capable of accelerating the vehicle to speeds up to 15 mph (24 kph) on electric power alone. The Prius was honored as the 2004 North American Car of the Year.
The Toyota Prius One of the main goals of the Toyota Prius is to improve emissions in urban driving. To accomplish this, Toyota has designed a parallel hybrid powertrain, called the Toyota Hybrid System (THS), that adds some of the benefits of a series hybrid.
Unlike Honda, Toyota has focused primarily on the powertrain to achieve its emissions and mileage goals. The Prius weighs 2,900 pounds (1,315 kg) and has as much interior space and trunk space as a Toyota Corolla. Figure 8 provides a layout of all the pieces.
Efficiency and Reduced EmissionsThe Prius mainly relies on two features to optimize efficiency and reduce emissions:
• Its engine only runs at an efficient speed and load - In order to reduce emissions, the Prius can accelerate to a speed of about 40 mph (64 kph) before switching on the gasoline engine. The engine only starts once the vehicle has passed a certain speed. And once the engine starts, it operates in a narrow speed band.
• It uses a unique power split device - Gasoline engines can be tuned to run most efficiently in certain speed and load ranges. The power split device on the Prius, which we'll talk about in a minute, allows the engine to stay in its most efficient load and speed range most of the time.
Toyota designed the 1.5-liter engine in the Prius to run at a maximum speed of only 5,000 rpm, where it makes 76 horsepower. Keeping the maximum speed of the engine low allows for the use of lighter components that improve efficiency.
The electric motor on the Prius is rated at 67 horsepower from 1,040-5,600 rpm. It produces 295 pound-feet of torque from 0 to 400 rpm, which is more than enough to get the car going without the aid of the gasoline engine.
The "Power Split Device"The power split device is the heart of the Toyota Prius. This is a clever gearbox that hooks the gasoline engine, generator and electric motor together. It allows the car to operate like a parallel hybrid -- the electric motor can power the car by itself, the gas engine can power the car by itself or they can power the car together.
The power split device alsto allows the car to operate like a series hybrid -- the gasoline engine can operate independently of the vehicle speed, charging the batteries or providing power to the wheels as needed. It also acts as a continuously variable transmission (CVT), eliminating the need for a manual or automatic transmission. Finally, because the power split device allows the generator to start the engine, the car does not need a starter. The power split device is a planetary gear set.
The electric motor is connected to the ring gear of the gear set. It is also directly connected to the differential, which drives the wheels. So, whatever speed the electric motor and ring gear spin at determines the speed of the car.
The generator is connected to the sun gear of the gear set, and the engine is connected to the planet carrier. The speed of the ring gear depends on all three components, so they all have to work together at all times to control the output speed.
Videos of the future cars
Relaxation and reference
In 1769, the very first self-propelled road vehicle was a military tractor invented by French engineer and mechanic, Nicolas Joseph Cugnot (1725 - 1804). Cugnot used a steam engine to power his vehicle, built under his instructions at the Paris Arsenal by mechanic Brezin.
It was used by the French Army to haul artillery at a whopping speed of 2 1/2 mph on only three wheels. The vehicle had to stop every ten to fifteen minutes to build up steam power. The steam engine and boiler were separate from the rest of the vehicle and placed in the front (see engraving above). The following year (1770), Cugnot built a steam-powered tricycle that carried four passengers.
In 1771, Cugnot drove one of his road vehicles into a stone wall, making Cugnot the first person to get into a motor vehicle accident. This was the beginning of bad luck for the inventor. After one of Cugnot's patrons died and the other was exiled, the money for Cugnot's road vehicle experiments ended.
Steam engines powered cars by burning fuel that heated water in a boiler, creating steam that expanded and pushed pistons that turned the crankshaft, which then turned the wheels. During the early history of self-propelled vehicles - both road and railroad vehicles were being developed with steam engines. (Cugnot also designed two steam locomotives with engines that never worked well.) Steam engines added so much weight to a vehicle that they proved a poor design for road vehicles; however, steam engines were very successfully used in locomotives. Historians, who accept that early steam-powered road vehicles were automobiles, feel that Nicolas Cugnot was the inventor of the first automobile.
In terms of the lives of average people, there is little doubt that the automobile is the most revolutionary invention in the history of transportation since the wheel.The basic premise of the automobile is simple; choose a wheeled vehicle from the many types typically pulled by horses or oxen, add a motor and create a self-propelled, personal transportation vehicle.
The earliest ancestor of the modern automobile is probably the Fardier, a three-wheeled, steam-powered, 2.3-mph vehicle built in 1771 by Nicolas Joseph Cugnot for the French minister of war. This cumbersome machine was never put into production because it was much slower and harder to operate than a horse-drawn vehicle.
Amedee Bollee, also a Frenchman, built an improved 12-passenger steam car in 1873, but the steam engine proved impractical for a machine that was intended to challenge the speed of a horse-and-buggy. The invention of the practical automobile had to await the invention of a workable internal combustion engine.
The milestone vehicle was built in Germany in 1889 by Gottlieb Daimler and Wilhelm Maybach. Powered by a 1.5 hp, two-cylinder gasoline engine, it had a four-speed transmission and traveled at 10 mph. Another German, Karl Benz, also built a gasoline-powered car the same year. The gasoline-powered automobile, or motor car, remained largely a curiosity for the rest of the nineteenth century, with only a handful being manufactured in Europe and the United States.
The first automobile to be produced in quantity was the 1901 Curved Dash Oldsmobile, which was built in the United States by Ransom E. Olds. Modern automobile mass production, and its use of the modern industrial assembly line, is credited to Henry Ford of Detroit, Michigan, who had built his first gasoline-powered car in 1896. Ford began producing his Model T in 1908, and by 1927, when it was discontinued, over 18 million had rolled off the assembly line.
Bai 2:
About 15000 separate parts are put together to make an automobile. These parts are grouped into several systems. Each system is made up of two or more parts that work together to perform a specific job. Examples are such jobs as braking and steering.
Automotive vehicles are produces in a large variety of sizes and shapes. All have the same basic parts and systems. Today, many of these systems are controlled electronically by one or more electronic control modules (ECM). Some times an ECM is called a computer.
The basic parts and systems in an automobile are the major components. These include:
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A power train
The drive or power train carries power from the engine to the drive wheels (Fig.-18). Major power-train parts may include the clutch, transmission or transaxle, transfer case, driveshaft, and differential. Fig 1 - 9 Shows the layout of these parts for front-wheel drive, rear-wheel drive, and four-wheel drive.
Transmissions and transaxles may either manual or automatic. Automatic transmissions and transaxles automatically shift from one gear ratio to another. The driver takes no action. Manual transmissions and transaxles are shifted by hand.
To shift from one gear radio to another, the driver depresses the clutch pedal and moves the shift lever.
The clutch
Vehicles with a manual transmission or transaxle have a clutch (fig 1.19). It is between the engine and the transmission of transaxle. Before shifting, this disconnects the engine from the transmission or transaxle. Parts in these units may be damages by trying to shift while under load.
Transmissions and transaxles
Transmissions and transaxles look different. They are similar in some ways. Both are gear boxes made up of a metal case containing gears and shafts. The case is filled with oil. The transaxle provides several different forward gear ratios between the engine and the drive wheels Gear ratio is the difference in rotating speed between the engine and the wheels Other positions are reverse and neutral. Reverse allows the vehicle to move backward. Neutral disengages all gears for starting and running the engine without moving the vehicle When an engine is turning slowly, it cannot produce enough power to get the vehicle moving. The transmission gear ratios provide the necessary increase in engine torque supplied by the engine that turns the wheels to move the car.
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A steering system
so the driver can control the direction of vehicle travelThe steering system enables to driver to turn the front wheels left or right. This changes the direction of vehicle travel. Steering starts at the steering wheel in front of the driver. As it is turned, shafts and gears act on linkage, which connects to the front wheels. The wheels swing to the right or left.
The vehicle then follows the direction in which the front wheels point.A few vehicles have four-wheel steering. When the front wheels swing to one side for steering, the rear wheels also swing slightly. This can make parking easier and improve high-speed stability. Four wheel steering is controlled either mechanically or electronically. However, the rear-wheel steering movement is very small compared to that of the front wheel stering.
The engine provides the power to move the car. However, electricity powers most devices on the car The starting motor requires electricity to crank the engine. The ignition system requires electricity to deliver sparks to the cylinders. The fuel-injection system needs electricity to provide fuel. The lights, horns, radio, and air conditioner all require electricity to operate.
The car ha two sources of electricity. One is the battery. The other is the alternator in the charging system. The battery supplies electricity while the engine is off and for cranking the engine. After the engine starts, the alternator recharges the battery and supplies power for the electrical load.
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Springs, shock absorbers, and related parts between the wheels and the car body make up the suspension system spring at each wheel supports the weight of the vehicle and the load it is carrying.
The springs allow the wheels to move up and down as they meet holes and bumps in the road. As the wheels do this, the springs absorb most of the motion. Little up and down movement reaches the body.
A shock absorber at each wheel helps limit spring travel and wheel bounce. Automobile suspension systems use four types of springs. These are coil springs, leaf springs, torsion-bar springs, and air spring Some cars have electronic ride control. It automatically changes the firmness of the shock absorber to suit road conditions. Other cars have an electronic air suspension system. It is similar to electronic ride control. However, rubber bags filled with air (“air springs”) replace the metal springs.
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The engine provides the power to move the car. However, electricity powers most devices on the car The starting motor requires electricity to crank the engine. The ignition system requires electricity to deliver sparks to the cylinders. The fuel-injection system needs electricity to provide fuel. The lights, horns, radio, and air conditioner all require electricity to operate.
The car ha two sources of electricity. One is the battery. The other is the alternator in the charging system. The battery supplies electricity while the engine is off and for cranking the engine. After the engine starts, the alternator recharges the battery and supplies power for the electrical load.
Many devices and systems on the car require an electronic control system for safe and proper operation. They include electronic control of automatic transmissions and transaxles, suspension and steering, and antilock-brake and traction-control systems.
A basic control system has three parts. These are the inputs, the control unit, and the outputs. The inputs are switches and sensors. They provide information to the electronic control module (ECM). It then decides how much change to make, if any.
Then the ECM signals the output devices or actuators to take the required action.
On most engines, an electronic engine control systems (EEC) controls the ignition and fuel injection systems. In the EEC system, the electronic control module usually has a self-diagnostic capability. This means memory stores information about faults or malfunctions that have occurred and perhaps disappeared. A malfunction is an improper or incorrect operation. When recalled from the memory, this stored information helps the technician diagnose and repair the vehicle.
Bai 3:
Introduction
Have you ever opened the hood of your car and wondered what was going on in there? A car engine can look like a big confusing jumble of metal, tubes and wires to the uninitiated.
You might want to know what's going on simply out of curiosity. Or perhaps you are buying a new car, and you hear things like "3.0 liter -6" and "dual overhead cams" and "tuned port fuel injection." What does all of that mean?
If you have ever wondered about this kind of stuff, then read on -- In this article, we'll discuss the basic idea behind an engine and then go into detail about how all the pieces fit together, what can go wrong and how to increase performance.
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The BasicsThe purpose of a gasoline car engine is to convert gasoline into motion so that your car can move. Currently the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is an internal combustion engine -- combustion takes place internally. Two things to note:
• There are different kinds of internal combustion engines. Diesel engines are one form and gas turbine engines are another. See also the articles on HEMI engines, rotary engines and two-stroke engines. Each has its own advantages and disadvantages.
• There is such a thing as an external combustion engine. A steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. Internal combustion is a lot more efficient (takes less fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and GM using steam engines.
Almost all cars today use a reciprocating internal combustion engine because this engine is:
• Relatively efficient (compared to an external combustion engine)
• Relatively inexpensive (compared to a gas turbine)
• Relatively easy to refuel (compared to an electric car)
These advantages beat any other existing technology for moving a car around.
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Combustion is Key To understand the basic idea behind how a reciprocating internal combustion engine works, it is helpful to have a good mental image of how "internal combustion" works. One good example is an old Revolutionary War cannon. You have probably seen these in movies, where the soldiers load the cannon with gun powder and a cannon ball and light it. That is internal combustion, but it is hard to imagine that having anything to do with engines.
A more relevant example might be this: Say that you took a big piece of plastic sewer pipe, maybe 3 inches in diameter and 3 feet long, and you put a cap on one end of it. Then say that you sprayed a little WD-40 into the pipe, or put in a tiny drop of gasoline. Then say that you stuffed a potato down the pipe.
I am not recommending that you do this! But say you did... What we have here is a device commonly known as a potato cannon. When you introduce a spark, you can ignite the fuel.
What is interesting, and the reason we are talking about such a device, is that a potato cannon can launch a potato about 500 feet through the air! There is a huge amount of energy in a tiny drop of gasoline
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Internal CombustionThe potato cannon uses the basic principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!
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Counting cycleThe core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.
Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing-cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles
Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are:
• Intake stroke
• Compression stroke
• Combustion stroke
• Exhaust stroke
Displacement
The combustion chamber is the area where compression and combustion take place. As the piston moves up and down, you can see that the size of the combustion chamber changes. It has some maximum volume as well as a minimum volume. The difference between the maximum and minimum is called the displacement and is measured in liters or CCs (Cubic Centimeters, where 1,000 cubic centimeters equals a liter).
Here are some examples:
• A chainsaw might have a 40 cc engine.
• A motorcycle might have a 500 cc or a 750 cc engine.
• A sports car might have a 5.0 liter (5,000 cc) engine.
Most normal car engines fall somewhere between 1.5 liter (1,500 cc) and 4.0 liters (4,000 cc)
If you have a 4-cylinder engine and each cylinder displaces half a liter, then the entire engine is a "2.0 liter engine." If each cylinder displaces half a liter and there are six cylinders arranged in a V configuration, you have a "3.0 liter V-6."
Generally, the displacement tells you something about how much power an engine can produce. A cylinder that displaces half a liter can hold twice as much fuel/air mixture as a cylinder that displaces a quarter of a liter, and therefore you would expect about twice as much power from the larger cylinder (if everything else is equal). So a 2.0 liter engine is roughly half as powerful as a 4.0 liter engine.
You can get more displacement in an engine either by increasing the number of cylinders or by making the combustion chambers of all the cylinders bigger (or both).
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What Can Go Wrong?So you go out one morning and your engine will turn over but it won't start... What could be wrong? Now that you know how an engine works, you can understand the basic things that can keep an engine from running. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three." Based on the simple engine we have been discussing, here is a quick run-down on how these problems affect your engine:
Bad fuel mix - A bad fuel mix can occur in several ways:
You are out of gas, so the engine is getting air but no fuel.
The air intake might be clogged, so there is fuel but not enough air.
The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.
There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.
Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:
Your piston rings are worn (allowing air/fuel to leak past the piston during compression).
The intake or exhaust valves are not sealing properly, again allowing a leak during compression.
There is a hole in the cylinder.
The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.
Lack of spark - The spark might be nonexistent or weak for a number of reasons:
If your spark plug or the wire leading to it is worn out, the spark will be weak.
If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark.
If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.
Many other things can go wrong. For example:
If the battery is dead, you cannot turn over the engine to start it.
If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run.
If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run.
If someone sticks a potato up your tailpipe, exhaust cannot exit the cylinder so the engine will not run.
If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.
In a properly running engine, all of these factors are within tolerance.
As you can see, an engine has a number of systems that help it do its job of converting fuel into motion. Most of these subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines in the following sections
○The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down,
Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams."
Valve TrainsThe valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down.
Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves, as you see in Figure 5. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams."
Ignition SystemThe ignition system produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness.
Cooling SystemThe cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.
Air intake Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor.
Starting SystemThe starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:
All of the internal friction caused by the piston rings
The compression pressure of any cylinder(s) that happens to be in the compression stroke
The energy needed to open and close valves with the camshaft
All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.
Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor.
Lubrication SystemThe lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings that allow things like the crankshaft and camshafts to rotate freely. In most cars, oil is sucked out of the oil pan by the oil pump, run through the oil filter to remove any grit, and then squirted under high pressure onto bearings and the cylinder walls. The oil then trickles down into the sump, where it is collected again and the cycle repeats.
Fuel SystemThe fuel system pumps gas from the gas tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.
In carburetion, a device called a carburetor mixes gas into air as the air flows into the engine.
In a fuel-injected engine, the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).
Exhaust SystemThe exhaust system includes the exhaust pipe and the muffler. Without a muffler, what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens the sound. The exhaust system also includes a catalytic converter.
Emission ControlThe emission control system in modern cars consists of a catalytic converter, a collection of sensors and actuators, and a computer to monitor and adjust everything. For example, the catalytic converter uses a catalyst and oxygen to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available for the catalyst to work and adjusts things if necessary.
Produce more power
Using all of this information, you can begin to see that there are lots of different ways to make an engine perform better. Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient.
Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit.
Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power.
Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder. See How Turbochargers Work for details.
Cool the incoming air - Compressing air raises its temperature. However, you would like to have the coolest air possible in the cylinder because the hotter the air is, the less it will expand when combustion takes place. Therefore, many turbocharged and supercharged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder.
Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Air resistance can be lessened dramatically by putting two intake valves in each cylinder. Some newer cars are also using polished intake manifolds to eliminate air resistance there. Bigger air filters can also improve air flow.
Let exhaust exit more easily - If air resistance makes it hard for exhaust to exit a cylinder, it robs the engine of power. Air resistance can be lessened by adding a second exhaust valve to each cylinder (a car with two intake and two exhaust valves has four valves per cylinder, which improves performance -- when you hear a car ad tell you the car has four cylinders and 16 valves, what the ad is saying is that the engine has four valves per cylinder). If the exhaust pipe is too small or the muffler has a lot of air resistance, this can cause back-pressure, which has the same effect. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. When you hear that a car has "dual exhaust," the goal is to improve the flow of exhaust by having two exhaust pipes instead of one.
Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction, it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes.
Inject the fuel - Fuel injection allows very precise metering of fuel to each cylinder. This improves performance and fuel economy.
Bai 4:
Introduction the Hybrid
Have you pulled your car up to the gas pump lately and been shocked by the high price of gasoline? As the pump clicked past $20 or $30, maybe you thought about trading in that SUV for something that gets better mileage. Or maybe you're worried that your car is contributing to the greenhouse effect. Or maybe you just want to have the coolest car on the block.
The auto industry now has the technology that might answer all of these needs. It's the hybrid car, and a few manufacturers are selling their versions in the United States. You're probably aware of hybrid cars because they've been in the news a lot. In fact, most automobile manufacturers have announced plans to manufacture their own versions -- you can even expect some hybrid SUVs to hit the streets this year.
How does a hybrid automobile work? What goes on under the hood to give you 20 or 30 more miles per gallon than the standard automobile? And does it pollute less just because it gets better gas mileage? In this article, we'll help you understand how this amazing technology works. We'll show you what is going on in the Toyota and Honda hybrids, and even give you some advice about how to drive one for maximum efficiency!
What Makes it a "Hybrid"?Any vehicle is a hybrid when it combines two or more sources of power. In fact, many people have probably owned a hybrid vehicle at some point. For example, a mo-ped (a motorized pedal bike) is a type of hybrid because it combines the power of a gasoline engine with the pedal power of its rider.
Hybrid vehicles are all around us. Most of the locomotives we see pulling trains are diesel-electric hybrids. Cities like Seattle have diesel-electric buses -- these can draw electric power from overhead wires or run on diesel when they are away from the wires. Giant mining trucks are often diesel-electric hybrids.
Submarines are also hybrid vehicles -- some the engine on a hybrid is smaller and uses advanced technologies to reduce emissions and increase efficiency.
• Fuel tank - The fuel tank in a hybrid is the energy storage device for the gasoline engine. Gasoline has a much higher energy density than batteries do. For example, it takes about 1,000 pounds of batteries to store as much energy as 1 gallon (7 pounds) of gasoline.
• Electric motor - The electric motor on a hybrid car is very sophisticated. Advanced electronics allow it to act as a motor as well as a generator. For example, when it needs to, it can draw energy from the batteries to accelerate the car. But acting as a generator, it can slow the car down and return energy to the batteries.
• Generator - The generator is similar to an electric motor, but it acts only to produce electrical power. It is used mostly on series hybrids.
• Batteries - The batteries in a hybrid car are the energy storage device for the electric motor. Unlike the gasoline in the fuel tank, which can only power the gasoline engine, the electric motor on a hybrid car can put energy into the batteries as well as draw energy from them.
• Transmission - The transmission on a hybrid car performs the same basic function as the transmission on a conventional car. Some hybrids, like the Honda Insight, have conventional transmissions. Others, like the Toyota Prius, have radically different ones, which we'll talk about later.
Why Build Such a Complex Car?You might wonder why anyone would build such a complicated machine when most people are perfectly happy with their gasoline-powered cars. The reason is twofold: to reduce tailpipe emissions and to improve mileage. These goals are actually tightly interwoven.
California emissions standards dictate how much of each type of pollution a car is allowed to emit in California. The amount is usually specified in grams per mile (g/mi). For example, the low emissions vehicle (LEV) standard allows 3.4 g/mi of carbon monoxide.
The key thing here is that the amount of pollution allowed does not depend on the mileage your car gets. But a car that burns twice as much gas to go a mile will generate approximately twice as much pollution. That pollution will have to be removed by the emissions control equipment on the car. So decreasing the fuel consumption of the car is one of the surest ways to decrease emissions.
Carbon dioxide (CO2) is another type of pollution a car produces. The U.S. government does not regulate it, but scientists suspect that it contributes to global warming. Since it is not regulated, a car has no devices for removing CO2 from the exhaust, so a car that burns twice as much gas adds twice as much CO2 to the atmosphere.
Automakers in the U.S. have another strong incentive to improve mileage. They are required by law to meet Corporate Average Fuel Economy (CAFE) standards. The current standards require that the average mileage of all the new cars sold by an automaker should be 27.5 mpg (8.55 liters per 100 km). This means that if an automaker sells one hybrid car that gets 60 mpg (3.92 liters per 100 km), it can then sell four big, expensive luxury cars that only get 20 mpg (11.76 liters per 100 km)!
Evolution of the HybridThe hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while overcoming the shortcomings of an electric car.
The Problem with Gas-powered CarsTo be useful to you or me, a car must meet certain minimum requirements. The car should be able to:
• Drive at least 300 miles (482 km) between re-fueling
• Be refueled quickly and easily
• Keep up with the other traffic on the road
A gasoline car meets these requirements but produces a relatively large amount of pollution and generally gets poor gas mileage. An electric car, on the other hand, produces almost no pollution, but it can only go 50 to 100 miles (80 to 161 km) between charges. And the problem has been that it is very slow and inconvenient to recharge.
A driver's desire for quick acceleration causes our cars to be much less efficient than they could be. You may have noticed that a car with a less powerful engine gets better gas mileage than an identical car with a more powerful engine. Just look at the window stickers on new cars at a dealership for a city and highway mpg comparison.
The amazing thing is that most of what we require a car to do uses only a small percentage of its horsepower! When you are driving along the freeway at 60 mph (96.6 kph), your car engine has to provide the power to do three things:
Overcome the aerodynamic drag caused by pushing the car through the air
• Overcome all of the friction in the car's components such as the tires, transmission, axles and brakes
• Provide power for accessories like air conditioning, power steering and headlights
For most cars, doing all this requires less than 20 horsepower! So, why do you need a car with 200 horsepower? So you can "floor it," which is the only time you use all that power. The rest of the time, you use considerably less power than you have available.
Smaller Engines are More EfficientMost cars require a relatively big engine to produce enough power to accelerate the car quickly. In a small engine, however, the efficiency can be improved by using smaller, lighter parts, by reducing the number of cylinders and by operating the engine closer to its maximum load.
There are several reasons why smaller engines are more efficient than big ones:
• The big engine is heavier than the small engine, so the car uses extra energy every time it accelerates or drives up a hill.
• The pistons and other internal components are heavier, requiring more energy each time they go up and down in the cylinder.
• The displacement of the cylinders is larger, so more fuel is required by each cylinder.
• Bigger engines usually have more cylinders, and each cylinder uses fuel every time the engine fires, even if the car isn't moving.
This explains why two of the same model cars with different engines can get different mileage. If both cars are driving along the freeway at the same speed, the one with the smaller engine uses less energy. Both engines have to output the same amount of power to drive the car, but the small engine uses less power to drive itself.
Hybrid PerformanceThe key to a hybrid car is that the gasoline engine can be much smaller than the one in a conventional car and therefore more efficient. But how can this smaller engine provide the power your car needs to keep up with the more powerful cars on the road?
Let's compare a car like the Chevy Camaro, with its big V-8 engine, to our hybrid car with its small gas engine and electric motor. The engine in the Camaro has more than enough power to handle any driving situation. The engine in the hybrid car is powerful enough to move the car along on the freeway, but when it needs to get the car moving in a hurry, or go up a steep hill, it needs help. That "help" comes from the electric motor and battery -- this system steps in to provide the necessary extra power.
The gas engine on a conventional car is sized for the peak power requirement (those few times when you floor the accelerator pedal). In fact, most drivers use the peak power of their engines less than one percent of the time. The hybrid car uses a much smaller engine, one that is sized closer to the average power requirement than to the peak power.
Hybrid EfficiencyBesides a smaller, more efficient engine, today's hybrids use many other tricks to increase fuel efficiency. Some of those tricks will help any type of car get better mileage, and some only apply to a hybrid. To squeeze every last mile out of a gallon of gasoline, a hybrid car can:
• Recover energy and store it in the battery - Whenever you step on the brake pedal in your car, you are removing energy from the car. The faster a car is going, the more kinetic energy it has. The brakes of a car remove this energy and dissipate it in the form of heat. A hybrid car can capture some of this energy and store it in the battery to use later. It does this by using "regenerative braking." That is, instead of just using the brakes to stop the car, the electric motor that drives the hybrid can also slow the car. In this mode, the electric motor acts as a generator and charges the batteries while the car is slowing down.
• Sometimes shut off the engine - A hybrid car does not need to rely on the gasoline engine all of the time because it has an alternate power source -- the electric motor and batteries. So the hybrid car can sometimes turn off the gasoline engine, for example when the vehicle is stopped at a red light.
• Use advanced aerodynamics to reduce drag - When you are driving on the freeway, most of the work your engine does goes into pushing the car through the air. This force is known as aerodynamic drag. This drag force can be reduced in a variety of ways. One sure way is to reduce the frontal area of the car. Think of how a big SUV has to push a much greater area through the air than a tiny sports car.
Reducing disturbances around objects that stick out from the car or eliminating them altogether can also help to improve the aerodynamics. For example, covers over the wheel housings smooth the airflow and reduce drag. And sometimes, mirrors are replaced with small cameras.
• Use low-rolling resistance tires - The tires on most cars are optimized to give a smooth ride, minimize noise, and provide good traction in a variety of weather conditions. But they are rarely optimized for efficiency. In fact, the tires cause a surprising amount of drag while you are driving. Hybrid cars use special tires that are both stiffer and inflated to a higher pressure than conventional tires. The result is that they cause about half the drag of regular tires.
Use lightweight materials - Reducing the overall weight of a car is one easy way to increase the mileage. A lighter vehicle uses less energy each time you accelerate or drive up a hill. Composite materials like carbon fiber or lightweight metals like aluminum and magnesium can be used to reduce weight. What's Available Now?Three hybrid cars are now available in the United States -- the Honda Civic Hybrid, the Honda Insight and the Toyota Prius. We will be discussing the latter two, and although both of these cars are hybrids, they are actually quite different in character.
Coming Soon!
Over the past four years, more than 100,000 hybrids have been sold in the United States. (The Prius and the Honda Civic Hybrid account for the majority of these sales.) Even though that's not a huge percentage of the more than 17 million new cars and trucks that are sold in the U.S. each year, it's enough of an incentive to get more manufacturers on the hybrid bandwagon. Analysts suggest that the market this year, alone, could muster up the sales of the past four combined.
Below are some of the models manufacturers soon plan to integrate into the consumer market.
The Honda Insightshows the layout of the Honda Insight, which is a simplified parallel hybrid. It has an electric motor coupled to the engine at the spot where the flywheel usually goes. Honda calls this system "Integrated Motor Assist." The Insight also has a conventional five-speed manual transmission. For those of you that have trouble changing gears, or prefer an automatic transmission, the Insight CVT is now available. Prices start at $21,280.
The electric motor on the Insight helps in several ways. It can:
• Assist the gasoline engine, providing extra power while the car is accelerating or climbing a hill
• Provide some regenerative braking to capture energy during braking
• Start the engine, eliminating the need for a starter
However, the motor cannot power the car by itself; the gas engine must be running for the car to move. Insight Fuel EfficiencyBecause the Insight was designed to get the best mileage possible, Honda used all of the tricks discussed in the previous section. But the Insight relies mainly on three areas:
- It reduces the weight - Already a small car, the Insight uses a lightweight aluminum body and structure to further reduce weight. By making the car lightweight, Honda was able to use a smaller, lighter engine that could still maintain the performance level we have come to expect from our cars. The Insight weighs less than 1,900 pounds (862 kg), which is 500 pounds (227 kg) less than the lightest Honda Civic.
• It uses a small, efficient engine - The engine in the Insight, shown in Figure 7, weighs only 124 pounds (56 kg) and is a tiny, 1.0-liter three-cylinder that produces 67 horsepower at 5,700 rpm. It incorporates Honda's VTEC system and uses lean burn technology to maximize efficiency. The Insight achieves an EPA mileage rating of 61 mpg/city and 70 mpg/highway. Also, with the additional power provided by the small electric motor, this system is able to accelerate the Insight from 0 to 60 mph in about 11 seconds.
With the electric motor running, the Insight produces 73 horsepower at 5,700 rpm. If you compare that to the engine horsepower alone, it looks like the electric motor only adds 6 horsepower. But the real effectiveness of the electric motor occurs at lower engine speeds. The electric motor on the Insight is rated at 10 kilowatts (about 13 horsepower) at 3,000 rpm.
It's the peak torque numbers that really tell the story. Without the electric motor, the Insight makes its peak torque of 66 pound-feet at 4,800 rpm. With the electric motor, it makes 91 pound-feet at 2,000 rpm. So the motor adds a lot of torque to the low end of the speed range, where the engine is weaker. This is a nice compromise that allows Honda to give a very small engine the feel of a much larger one.
It uses advanced aerodynamics - The Honda Insight is designed using the classical teardrop shape: The back of the car is narrower than the front. (Note that real teardrops do not behave this way aerodynamically. The rear wheels are partially covered by bodywork to provide a smoother shape, and some parts of the underside of the car are enclosed with plastic panels. These tricks result in a drag coefficient of 0.25, which makes it one of the most aerodynamic cars on the market.
Driving the InsightThe Insight is actually not very different from a conventional car once you get behind the wheel. When you accelerate, the gas engine does most of the work. If you accelerate quickly, the electric motor kicks in to provide a little extra power.
When you are cruising along the freeway, the gas engine is doing all of the work. When you slow down by hitting the brakes or letting off the gas, the electric motor kicks in to generate a little electricity to charge the batteries. You never have to plug the Insight into an electrical outlet; the motor generates all of the power needed to charge the battery.
One interesting thing to note is that in the Insight, the manual transmission is separated from the engine and motor by the clutch. This means that if you are the type of driver who likes to put the clutch in or put the car in neutral when you slow down to a stop, you are not going to get any regenerative braking. In order to recover energy when you slow down, the car has to be in gear.
The Honda Insight price starts around $19,570, and the Toyota Prius starts around $20,510. Both cars have a gasoline engine, an electric motor and batteries, but that is where the similarities end.
The Honda Insight, which was introduced in early 2000 in the United States, is designed to get the best possible mileage. Honda used every trick in the book to make the car as efficient as it can be. The Insight is a small, lightweight two-seater with a tiny, high-efficiency gas engine.
The Toyota Prius, which came out in Japan at the end of 1997, is designed to reduce emissions in urban areas. It meets California's super ultra low emissions vehicle (SULEV) standard. It is a four-door sedan that seats five, and the powertrain is capable of accelerating the vehicle to speeds up to 15 mph (24 kph) on electric power alone. The Prius was honored as the 2004 North American Car of the Year.
The Toyota Prius One of the main goals of the Toyota Prius is to improve emissions in urban driving. To accomplish this, Toyota has designed a parallel hybrid powertrain, called the Toyota Hybrid System (THS), that adds some of the benefits of a series hybrid.
Unlike Honda, Toyota has focused primarily on the powertrain to achieve its emissions and mileage goals. The Prius weighs 2,900 pounds (1,315 kg) and has as much interior space and trunk space as a Toyota Corolla. Figure 8 provides a layout of all the pieces.
Efficiency and Reduced EmissionsThe Prius mainly relies on two features to optimize efficiency and reduce emissions:
• Its engine only runs at an efficient speed and load - In order to reduce emissions, the Prius can accelerate to a speed of about 40 mph (64 kph) before switching on the gasoline engine. The engine only starts once the vehicle has passed a certain speed. And once the engine starts, it operates in a narrow speed band.
• It uses a unique power split device - Gasoline engines can be tuned to run most efficiently in certain speed and load ranges. The power split device on the Prius, which we'll talk about in a minute, allows the engine to stay in its most efficient load and speed range most of the time.
Toyota designed the 1.5-liter engine in the Prius to run at a maximum speed of only 5,000 rpm, where it makes 76 horsepower. Keeping the maximum speed of the engine low allows for the use of lighter components that improve efficiency.
The electric motor on the Prius is rated at 67 horsepower from 1,040-5,600 rpm. It produces 295 pound-feet of torque from 0 to 400 rpm, which is more than enough to get the car going without the aid of the gasoline engine.
The "Power Split Device"The power split device is the heart of the Toyota Prius. This is a clever gearbox that hooks the gasoline engine, generator and electric motor together. It allows the car to operate like a parallel hybrid -- the electric motor can power the car by itself, the gas engine can power the car by itself or they can power the car together.
The power split device alsto allows the car to operate like a series hybrid -- the gasoline engine can operate independently of the vehicle speed, charging the batteries or providing power to the wheels as needed. It also acts as a continuously variable transmission (CVT), eliminating the need for a manual or automatic transmission. Finally, because the power split device allows the generator to start the engine, the car does not need a starter. The power split device is a planetary gear set.
The electric motor is connected to the ring gear of the gear set. It is also directly connected to the differential, which drives the wheels. So, whatever speed the electric motor and ring gear spin at determines the speed of the car.
The generator is connected to the sun gear of the gear set, and the engine is connected to the planet carrier. The speed of the ring gear depends on all three components, so they all have to work together at all times to control the output speed.
Videos of the future cars
Relaxation and reference
