Automotive Engine Systems and Components
Domain focus
Automotive Engine Systems and Components tests the four-stroke cycle, major castings and moving parts, valve train, timing, and basic engine measurements. Expect identification, function, and fault-reasoning items.
Core rules
- A four-stroke cycle needs two crankshaft revolutions: intake, compression, power, exhaust. The camshaft turns at half crankshaft speed in a four-stroke engine.
- The piston, rings, connecting rod, crankshaft, flywheel, cylinder head, valves, and camshaft have distinct functions; rings seal combustion gases and control oil.
- Valve clearance is measured with a feeler gauge at the specified position and temperature. Timing marks must align before assembly.
- Engine displacement = swept volume of one cylinder × number of cylinders; swept volume = (π/4) × bore² × stroke. Compression has both valves closed; power begins after ignition.
Worked example
A four-cylinder engine has bore 8 cm and stroke 9 cm. One cylinder volume = (π/4) × 8² × 9 = 452.4 cm³. Four cylinders give about 1,810 cm³, or 1.81 litres. The calculation uses consistent centimetre units and multiplies by cylinder count only after finding one swept volume.
Traps
Confusing bore with stroke, measuring valve clearance at the wrong stroke, ignoring timing marks, and mixing up power stroke with compression stroke cost marks.