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The four-stroke engine is more efficient when running at full throttle, while the opposite is the case for the two-stroke engine. When a small car under heavy load runs at half speed, the engine automatically switches to the two-cycle mode, which is then more efficient. The research on this showed a 27% reduction in fuel consumption. [8] [9]
Animation of a two-stroke engine. A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston (one up and one down movement) in one revolution of the crankshaft in contrast to a four-stroke engine which requires four strokes of the piston in two crankshaft revolutions to complete a power cycle.
Four-stroke engine - oil shown in yellow at the bottom. Most four-stroke engines use a crankcase that contains the engine's lubricating oil, as either a wet sump system or the less common dry sump system. Unlike a two-stroke (crankcase-compression) engine, the crankcase in a four-stroke engine is not used for the fuel/air mixture.
The amount of power generated by a piston engine is related to its size (cylinder volume), whether it is a two-stroke engine or four-stroke design, volumetric efficiency, losses, air-to-fuel ratio, the calorific value of the fuel, oxygen content of the air and speed .
Four-stroking is a condition of two-stroke engines where combustion occurs every four strokes or more, rather than every two. Though normal in some instances at idle, extremely high engine speeds, and when letting off the throttle, such firing is uneven, noisy and may, in cases of malfunction, damage the engine if allowed to continue unabated.
A distinctive feature of the PC50 is the use of a four-stroke engine, at a time almost all pedal-equipped mopeds used two-stroke engines. Honda's early development of 50 cc four-stroke engines was a result of Soichiro Honda's dislike of the sharp noise of two-stroke engines. [2] The PC50 used two different engines during its production.
Cutaway model of a MAN B&W two-stroke marine diesel engine with the piston rod attached to a crosshead. In the two-stroke cycle, the four stages of internal combustion engine operation (intake, compression, ignition, exhaust) occur in one 360° revolution of the crank shaft, whereas in a four-stroke engine they take two complete revolutions.
Engine 499 cc (30 cu in), 2-stroke, four-cylinder, liquid-cooled, reed valve induction with YPVS Bore Stroke 56.4 mm × 50.0 mm (2.22 in × 1.97 in) Compression Ratio 6.6:1 Fuel System Mikuni VM26SS 26 mm (1.0 in) carburettor x 4 Lubrication Yamaha Autolube two stroke injection, transmission gear pump. Ignition