ASVAB Auto Information practice

In a conventional four-stroke engine, intake draws the charge in, compression squeezes it, the power stroke turns released energy into piston motion, and exhaust removes burned gases.

The crankshaft converts piston motion into rotation. The camshaft controls valve timing. A spark-ignition engine uses spark plugs; a diesel engine normally ignites fuel through the heat of compressed air.

The fuel system supplies fuel, the intake system supplies air, and the ignition system initiates combustion in a spark-ignition engine. The exhaust system carries combustion gases away.

Lubrication reduces friction and wear and helps carry heat away. The cooling system controls engine temperature: coolant carries heat, the radiator transfers heat to air, and a thermostat regulates coolant flow in a conventional system.

The transmission changes the relationship between engine speed and drive-wheel speed. Lower gearing can provide greater wheel torque at a given engine torque, with a corresponding speed tradeoff.

A differential allows driven wheels to rotate at different speeds while turning. A clutch in a conventional manual transmission can disconnect the engine from the transmission for starting and gear changes.

Brakes slow a vehicle by converting motion energy mainly into heat. Steering changes the direction of the wheels. Suspension supports the vehicle while allowing wheels to respond to uneven surfaces.

Springs store and release energy as the suspension moves; dampers reduce continued bouncing. Learn the function of each component before using a symptom to compare possible faults.

A warning or symptom may have several causes. In a multiple-choice question, use the stated observations to identify which component or system is most consistent with the evidence.

Do not assume that every vehicle uses the same layout. Questions about a conventional engine or a named braking system apply to that setup, not automatically to every modern hybrid or electric vehicle.