Engine Fundamentals

How the four-stroke engine works and its major systems.

~8 min read·3 sections·4 key terms

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The Four Strokes

A four-stroke gasoline engine cycle: INTAKE (air/fuel in), COMPRESSION (piston compresses the mixture), POWER (spark ignites it, pushing the piston down), and EXHAUST (burned gases out). Remember 'Suck, Squeeze, Bang, Blow.'

The crankshaft converts the pistons' up-and-down motion into rotation. Valves (controlled by the camshaft) open and close to let air/fuel in and exhaust out.

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Key Components

• PISTONS & RINGS — move in the cylinders; rings seal compression and control oil. • CRANKSHAFT — converts motion to rotation. • CAMSHAFT & VALVES — time the intake/exhaust. • TIMING BELT/CHAIN — synchronizes the crankshaft and camshaft. On an INTERFERENCE engine, a broken timing belt can bend valves (serious damage).

Compression, spark, and fuel (in the right amounts and timing) are needed for combustion.

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Lubrication & Cooling

• LUBRICATION — engine oil reduces friction and wear, cools, and cleans. The oil pump circulates it; the filter removes debris. Low oil/pressure causes rapid engine damage. • COOLING — coolant (antifreeze + water) absorbs heat and releases it at the radiator; the THERMOSTAT regulates temperature, and the water pump circulates coolant.

Overheating warps heads and blows head gaskets — a top cause of major engine damage.

📖 Key Terms

Four-stroke cycle: Intake, compression, power, exhaust ('suck, squeeze, bang, blow').
Interference engine: An engine where a broken timing belt lets valves hit pistons.
Thermostat: Regulates engine temperature by controlling coolant flow.
Timing belt/chain: Synchronizes the crankshaft and camshaft.

💡 Exam Tips

▸Four strokes: intake, compression, power, exhaust.
▸On an interference engine, a broken timing belt can bend valves.
▸The thermostat regulates engine temperature.
▸Combustion needs compression, spark, and the right fuel mixture/timing.