Four-Stroke Engine

Four-Strokes

                    A four-stroke engine is an internal combustion engine in which the piston completes four  separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed: Intake: Also known as induction or suction.

Comparison of 4-Stroke & 2-Stroke Cycle Engine

• 4-STROKE ENGINE

1. All events are completed in 4-strokesof the piston or 2 revolution of crank shaft i.e.,there is one power stroke for every 2 revolution of crank shaft.
2. Contains valves and the valves are actuated by cam mechanism. 
3. The charge is directly admitted into the engine cylinder. 
4. Torque is not uniform, requires heavier flywheel.
5. Volumetric efficiency is more due to  more time for suction.
6. Thermal efficiency is high.

      4-Stroke & 2-Stroke Cycle

• 2-STROKE ENGINE 

1. All events are completed in 2-strokes of the piston or 1 revolution of crankshaft i.e., there is one power stroke for every revolution of crank shaft. 
2. Doesn't have valves and only ports are provided. There ports are closed by piston. 
3. The charge first enters the crankease, and therefore crank is made gas tight. 
4. Torque is more uniform, requires lighter flywheel. 
5. Volumetric efficiency is low due to lesser time for suction. 
6. Thermal efficiency is low.

4-stroke engine

We will see how the 4-stroke engine works.  See full video