If your car doesn't start in the morning, you should check three things first: the battery, the fuel level and the spark plugs. It is easy to repair these faults. If the battery is flat, you should recharge it. If this doesn't work, you should replace it. If the petrol tank is empty, fill it up. If the spark plugs are dirty, clean them, and if the gap in a spark plug is too narrow or too wide, adjust it to the correct width.
Section 12
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Let's look closer at the engine components that operate together to generate power. The basic unit of the engine is the piston which moves up and down inside a cylinder. As air is compressed in the cylinder, fuel is injected on top of the piston. Under high pressure the fuel mixes with the hot air end self-ignites causing combustion. The force of the combustion pushes the piston and connecting rod down turning the crankshaft and flywheel which drive other components.
During engine operation the piston goes through four strokes: intake, compression, power and exhaust. During the four strokes, the piston moves down and up to complete cycles.
Intake: During the intake stroke the piston moves down in the cylinder pulling air past an open intake valve into the combustion chamber.
Compression: During the compression stroke all valves are closed, and piston moves up in the cylinder compressing the air. As the air molecules are compressed the air temperature increases dramatically to about 1000° F (537° C). As the piston nears the top of its stroke, fuel is injected into the combustion chamber on top of the piston. The fuel mixes with the hot compressed air and causes combustion.
Power: During the power stroke the valves are closed as the forces from combustion push the piston and connecting rod down, thereby turning the crankshaft. The heat energy has now been converted into mechanical power.
Exhaust: During the exhaust stroke the inertial force of the turning flywheel helps continue the rotation of the crankshaft to push the piston up again in the cylinder forcing the burned gases out the open exhaust valve. This completes the four strokes of the piston. These four strokes are repeated over and over as the engine operates.
Diesel engine offers the following advantages over automotive-type gasoline engines:
Fuel economy
Diesel engines have higher compression ratios and therefore burn fuel more completely and efficiently.
Reliability
Diesel engines have no electrical ignition system to fail or be maintained. They are built with heavy-duty parts to withstand the higher compression ratios and to operate for long periods with minimum breakdown. In on-highway trucks for instance, diesel engines have a projected service life of many hundreds of thousands of miles.
Power
It depends on engine size, but diesel engines generally produce more torque and power output than gasoline engines.
QUESTIONS
1.What takes place in the combustion chamber during the intake stroke?
2.What takes place in the cylinder during the compression stroke?
3.What takes place in the combustion chamber during the power stroke?
4.What takes place in the combustion chamber during the exhaust stroke?
5.What advantages do diesel engines offer?
Section 13
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The Саr and the Environment
Most of us know that cars cause air pollution. Scientists tell us that if we don't do something soon, we will be unable to repair the damage that we are causing to our planet. What are some of the things we can do to help?
Buy a fuel-efficient car and keep it that way
Good gas is a way to stop pollution. Choose a car that is friendly to the environment when you buy one.
Keep your car tuned up
A car that badly tuned releases more pollutants into the air. If you keep track of your gas mileage, you'll know when something is wrong. A badly tuned car uses almost 10% more gas than a well-tuned car. Other ways to waste gas are:
Idling your car unnecessarily. If you are stopped for longer than a minute, it is more fuel efficient to turn off your engine.
Using dirty fuel filters. Dirty fuel filters waste gas.
Air Conditioner Maintenance. Of course, this causes a big problem for both us and our mechanics. Our mechanics will have to make sure that there are no leaks, and fix them if there are, before they can add any R-12 (freon) to our air conditioning systems. Naturally, this cost will be passed along to us.
Section 14
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