Engines Cycle
Two-stroke
This system manages to pack one power stroke into every two strokes of the piston (up-down). This is achieved by exhausting and re-charging the cylinder simultaneously. The steps involved here are:
1. Intake and exhaust occur at bottom dead center. Some form of pressure is needed, either crankcase compression or super-charging.
2. Compression stroke: Fuel-air mix compressed and ignited.
In case of Diesel: Air compressed, fuel injected and self ignited
3. Power stroke: piston is pushed downwards by the hot exhaust gases.
Four-stroke
Engines based on the four-stroke ("Otto cycle") have one power stroke for every four strokes (up-down-up-down) and employ spark plug ignition. Combustion occurs rapidly, and during combustion the volume varies little ("constant volume").They are used in cars, larger boats, some motorcycles, and many light aircraft. They are generally quieter, more efficient, and larger than their two-stroke counterparts.
The steps involved here are:
1. Intake stroke: Air and vaporized fuel are drawn in.
2. Compression stroke: Fuel vapor and air are compressed and ignited.
3. Combustion stroke: Fuel combusts and piston is pushed downwards.
4. Exhaust stroke: Exhaust is driven out. During the 1st, 2nd, and 4th stroke the piston is relying on power and the momentum generated by the other pistons.
In that case, a four cylinder engine would be less powerful than a six or eight cylinder engine.
Diesel cycle
Most truck and automotive diesel engines use a cycle reminiscent of a four-stroke cycle, but with a compression heating ignition system, rather than needing a separate ignition system. This variation is called the diesel cycle.In the diesel cycle, diesel fuel is injected directly into the cylinder so that combustion occurs at constant pressure, as the piston moves.
Diesel Engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol engine (known as a gasoline engine in North America) or gas engine (using a gaseous fuel, not gasoline), which uses the Otto cycle, in which an air-fuel mixture is ignited by a spark plug.
The diesel cycle was invented by Rudolf Diesel and it has the highest thermal efficiency of any regular internal or external combustion engine due to its very high compression ratio. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) often have a thermal efficiency which exceeds 50%.
The diesel is similar to the four stroke, but uses a different method to ignite the fuel.
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For more details on 2-Stoke & 4-Stoke Internal Combustion Engines, follow the link given below- Back<< Internal Combustion Engines
The diesel cycle was invented by Rudolf Diesel and it has the highest thermal efficiency of any regular internal or external combustion engine due to its very high compression ratio. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) often have a thermal efficiency which exceeds 50%.
The diesel is similar to the four stroke, but uses a different method to ignite the fuel.
For more details on 2-Stoke & 4-Stoke Internal Combustion Engines, follow the link given below- Back<< Internal Combustion Engines
Intake
The intake valve opens, and fresh air (containing no fuel), is drawn into the cylinder. Compression
As the piston rises, the air is compressed, causing its temperature to rise. At the end of the compression stroke, the air is hot enough to ignite fuel. Injection
Near the top of the compression stroke, the fuel injector drives fuel into the cylinder. The fuel immediately ignites upon contact with the hot compressed air. Power
As the fuel burns, the gas in the cylinder heats and expands, driving the piston. Exhaust
The exhaust valve opens, and the exhaust is driven out of the cylinder. 
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