In a conventional marine diesel engine the power is produced by hot compressed air igniting fuel sprayed under very high pressure into the cylinder head. A marine diesel engine does not use a carburetor to mix fuel and air or spark plugs to ignite the mixture. Newer engines use an electronic fuel injection system whereby fuel and air are mixed more thoroughly in the pre-combustion chamber before entering the cylinder. Most reciprocating piston internal combustion engines work on one of two mechanical cycles-either the four-stroke cycle or the two-stroke cycle. The Basic Four-Stroke Diesel Engine
From its name, it is obvious there are four strokes in one complete engine cycle. Compression stroke. With both valves closed, the piston moves from BDC to TDC, compressing the air. Power stroke. Exhaust stroke. The Two-Stroke Diesel Engine
The two-stroke engine uses two piston strokes to complete one power stroke and, therefore, fire twice as often as a four-stroke engine.
