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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]
Four-stroke cycle used in gasoline/petrol engines: intake (1), compression (2), power (3), and exhaust (4). The right blue side is the intake port and the left brown side is the exhaust port. The cylinder wall is a thin sleeve surrounding the piston head which creates a space for the combustion of fuel and the genesis of mechanical energy.
(A four-stroke engine requires four strokes of the piston to complete a power cycle, in two crankshaft revolutions.) In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust (or scavenging) functions occurring at the same time.
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.
The induction stroke is the first phase in a four-stroke (e.g. Otto cycle or Diesel cycle) engine.It involves the downward movement of the piston, creating a partial vacuum that draws an air-fuel mixture (or air alone, in the case of a direct injection engine) into the combustion chamber.
A "twingle" is a four-stroke twin-cylinder engine with an altered firing order designed to give power pulses similar to a single-cylinder four-stroke engine. Inline twins with a 360° crankpin offset or flat-twins can be easily converted into twingles by firing both of the cylinders at the same time and installing a camshaft or camshafts that ...
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.
The advantage of the split-single engine compared to a conventional two-stroke engine is that the split-single can give better exhaust scavenging while minimizing the loss of fresh fuel/air charge through the exhaust port. As a consequence, a split-single engine can deliver better economy, and may run better at small throttle openings.