BASIC ENGINE OPERATION
There are two basic types of gasoline-powered piston engines: Four-stroke and two-stroke.
FOUR-STROKE ENGINES This most common type of engine, found in cars, trucks and many motorcycles, goes through four “strokes” or “cycles” of operation:
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1. Intake As the piston moves downward, the intake valve opens, and a mixture of air and gasoline vapor (air/ fuel) is sucked into the cylinder. 2. Compression As the piston reaches its lowest point (bottom dead center) and then moves back upward, the intake valve closes, and the air/fuel mixture is compressed. 3. Power When the piston is near the top of its travel (top dead center), the spark plug “fires,” which ignites the air/fuel mixture. The pressure from the burning fuel forces the piston downward. 4. Exhaust As the piston then moves back upward, the exhaust valve opens, and the burnt gases are pushed out of the cylinder. The cycles then repeat. Four-Stroke Engine Advantages: Durable and efficient. Can be tuned for a combination of high power, low fuel consumption and low emissions. Four-Stroke Engine Disadvantages: Requires complex control systems to produce the optimal combination of power, fuel consumption and emissions.
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