Differentiate Between 2 Stroke & 4 Stroke Engines

Differentiate Between 2 Stroke & 4 Stroke Engines



Completes a single rotation of the crankshaft after completing one cycle. 

After completing one cycle, It completes 2 rotations of the crankshaft.

There are 3 ports in a cylinder block: Inlet port, exhaust port & transfer port. 

There are only 2 ports inlet and exhaust valves.

There is a fresh charge that mixes with the exhaust gas and the combustion chamber resulting in poor thermal efficiency.

Scavenging of exhaust gases is nearly complete due to better thermal efficiency.

Generally cooled, simple designed and easy to maintain.

Water cooling systems are complicated in design & maintenance is difficult.

Mechanical efficiency increases as the number of moving parts decreases. 

Mechanical efficiency is less as the number of moving parts are used. 

Lighter flywheel required - less cyclic oscillation due to working stroke at each revolution.

A heavier flywheel is required to limit cyclic oscillation as the motor's stroke is generated every two revolutions.

Advantages and Disadvantages of 2 Stroke and 4 Stroke Engine 

Advantages of 2 Stroke Engine

  1. Simple Design and Construction : It's easy because there are no valves, just inlet and outlet ports.

  1. More Powerful : In a two-stroke engine every alternate stroke is power stroke unlike four-stroke one in which power gets delivered once every four strokes this gives a significant power boost also the acceleration will be higher and power delivery will be uniform due to the same reason.

  1. Position doesn't matter : Two-stroke engine can work in any position as lubrication is done through the means of fuel (as the fuel passes by through the whole cylinder and crankcase).

Disadvantages of 2 Stroke Engine

  1. Less fuel efficiency  : For each piston power stroke, fuel is consumed with each reciprocating stroke, which makes the engine more fuel efficient, even though it produces uniform power.

  1. Oil addition could be expensive : Two-stroke engines require an oil-air-fuel mixture to lubricate the crankshaft and cylinder walls; these oils can empty your pocket.

  1. More Pollution : A 2 stroke engine produces a lot of pollution. The combustion of oil added in the mixture produces a lot of smoke which leads to air pollution.

  1. Wastage of fuel : Sometimes the fresh charge that is in the process of combustion goes out with the exhaust, resulting in a waste of fuel and also affecting the power delivered by the engine.

  1. Improper Combustion : The exhaust gases often get trapped inside the combustion chamber this makes the fresh charge impure therefore maximum power doesn't get delivered because of improper and incomplete combustion.

Advantages of 4 Stroke Engine

  1. More Torque : In general, four-stroke engines always make extra work than two-stroke engines at low RPM. Although two-stroke ones are hired to work at higher RPM, it has a lot to do with fuel efficiency.

  1. More fuel efficiency : Compared to 2 stroke engines, 4 stroke engines have greater fuel efficiency.

  1. Less pollution : As power is generated once every four strokes and also as no oil or lubricant is added to the fuel, a four-stroke engine produces less pollution.

  1. More durability : We all know that more the engine runs quicker it wears out two-stroke engines are designed for high RPM if an engine can go for 10,000 revolutions per minute before it wears out a four-stroke engine with 100 revolutions per minute will run for 100 minutes than the other two-stroke engine which has a higher RPM of 500 and we'll run for only 20 minutes.

  1. No extra addition of oil : Only moving parts need immediate lubrication; No additional oil or lubricant is added to the fuel.

Disadvantages of 4 Stroke Engine 

  1. Complicated Design : Four-stroke engines have complex valve mechanisms that are operated and controlled by gears and chains. Also, there are many parts to consider, which makes troubleshooting more difficult.

  1. Less Powerful : As power gets delivered once every two rotations of crankshaft for strokes hence four-stroke is less powerful.

  1. Expensive : A four-stroke engine has much more parts than a two-stroke engine so they often require repairs which leads to greater expense.


Agriculture Sprayers and Dusters by ASPEE Group Of Companies, India. www.aspee.com

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American Spring & Pressing Works Pvt. Ltd. popularly known as ASPEE, a pioneer in the field of agricultural equipment, was established in 1946.


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