Four-stroke internal combustion engine – valves, ignition and the work diagram

Design & TechnologyMechanical EngineeringAges 16–17

A cutaway view of one cylinder of a four-stroke engine: the piston, connecting rod, rotating crankshaft, and the intake and exhaust valves opening and closing in the right phase. Click Run to watch the four strokes — intake, compression, power (combustion and expansion), exhaust — play out over two crankshaft revolutions (720°), with the spark plug firing (petrol engine) or the injector spraying fuel (diesel engine) near the end of the compression stroke. The p–V work diagram is drawn in real time; change the rpm and load to see power and torque change.