Two Strokes & Four Strokes Diesel and Gas Engines

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 Two-Stroke Engines


A two-stroke engine is a combustion engine that completes the cycle in two movements of the piston compared to twice that number for a four-stroke engine.

This increased efficiency is accomplished by using the beginning of the compression stroke and the end of the combustion stroke to perform simultaneously the intake and exhaust (or scavenging) functions.

The four "cycles" (intake, compression, power, exhaust) occur in one revolution, while in a Two-stroke engine it occurs in two complete revolutions



INTAKE  &  EXHAUST

First Stroke: Intake + Exhaust for Gas engine

In a two-stroke gas engine, the mixture (Air, Gasoline + oil), is injected into the combustion chamber by differential pressure at the first stroke




Get here the Marine Diesel Engines Book where you can find all the information on this and many other topics.



INTAKE & EXHAUST (Diesel)

Toward the end of the stroke, the piston exposes the intake port, allowing the compressed fuel/air mixture in the crankcase to escape around the piston into the main cylinder. This expels the exhaust gasses out the exhaust port, usually controlled for the exhaust valves.

Unfortunately, some of the fresh fuel mixtures are usually expelled as well.


The Four-Stroke Cycle (Diesel Engines)



Intake Stroke

Intake Valves open  and  Exhaust valves  closed
Air enters during the intake stroke when the piston is going down.


Compression Stroke

Intake  &  Exhaust Valves remain closed. Air is compressed and just before the piston reaches the top dead center, the fuel is injected.



Learn more in the following video




Power Stroke

Intake  &  Exhaust Valves remain closed. The intake and exhaust valves remain closed to seal the combustion chamber.



Exhaust Stroke

Intake Valves closed and Exhaust Valves open. The exhaust valve opens as the piston moves up and forces the combustion gases out of the cylinder. Near TDC the exhaust valve closes, the intake valve opens, and the cycle starts again.



Schedule a Video Call with Mr. Lopez for remote troubleshooting


Learn more about Marine Technical Training at www.mttedu.org

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