Difference between 4 stroke and 2 stroke engine

In this post, I am going to tell you about the difference between two stroke and four stroke engines. The main difference between them is that in 2 stroke engine the crankshaft revolves two times to complete its working cycle whereas in 4 stroke, the crankshaft does 2 revolutions to complete its working cycle.

Let’s try to understand their differences in detail.

Two Stroke Engine

Difference between 4 stroke and 2 stroke engine

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Four Stroke Engine

Difference between 4 stroke and 2 stroke engine

Difference Between 2 Stroke and 4 Stroke Engines

S.No.Four stroke engineTwo stroke engine1.It has one power stroke for every two revolutions of the crankshaft.It has one power stroke for each revolution of the crankshaft.2.A heavy flywheel is required and the engine runs unbalanced because turning moment on the crankshaft is not even due to one power stroke for every two revolutions of the crankshaft.A lighter flywheel is required and the engine runs balanced because turning moment is more even due to one power stroke for each revolution of the crankshaft.3.Engine is heavy in Weight.Engine is lighter in weight.4.Engine design is complicated due to the valve mechanism.Engine design is simple due to the absence of valve mechanism.5.It is costlier.Less cost than 4 stroke engine. 

6.

Less mechanical efficiency due to more friction in many parts.More mechanical efficiency due to less friction on a few parts.7.More output due to full fresh charge intake and full burnt gas exhaust.Less output due to mixing of fresh charge with the hot burnt gases.8.The engine runs cooler. It means that Temperature runs on lower temperatures.Engine runs hotter. It means that the engine temperature is higher as compared with two stroke engines.9.The engine may be air-cooled or water-cooled.The engine is air-cooled.10.Less fuel consumption and complete burning of fuel.More fuel consumption and a small amount of fresh charge is mixed with exhaust gases.11.The engine requires more space.The engine requires less space.12.Complicated lubricating system.Simple lubricating system.13.Less noise is created by the engine.More noise is created by the engine.14.The engine consists of an inlet and exhaust valve.The engine consists of inlet and exhaust ports.15.More thermal efficiency.Less thermal efficiency.16.It consumes less lubricating oil.It consumes more lubricating oil.17.Less wear and tear of moving parts.More wear and tear of moving parts.18.Used in cars, buses, trucks, etc.Used in mopeds, scooters, motorcycles etc.

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Image Source: http://en.wikipedia.org/wiki/Four-stroke_engine

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2stroke / 4stroke

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What’s the difference between 2-stroke and 4-stroke engines?

 Fuel for a 2-stroke engine has a small amount of oil mixed into it. It is called a “2-stroke” because just one up and down movement of the piston—the 2 strokes—performs the full cycle of intake, compression, combustion and exhaust. No intake or exhaust valves are used and instead, small holes called scavenging ports in the cylinder wall are used for drawing in air and expelling exhaust. Because combustion takes place with each revolution of the crankshaft with a 2-stroke, this format puts out more power than a 4-stroke engine and the power has more instantaneous delivery. This are some reasons why 2-stroke engines have a long history of use on many different types of motorcycles.
 However, concern for more environmentally friendly performance grew and 4-stroke engines are now the norm because they inherently have better fuel economy and less exhaust smoke. As of 2019, the only 2-stroke motorcycles Yamaha makes are for closed-course competition and some models for export. Nonetheless, Yamaha 2-stroke products have a simple, lightweight construction and comparatively easy maintenance, and their high reliability keeps them popular in many regions. Today, Yamaha 2-stroke snowmobiles are used to traverse the icy cold environment of Russia, and our 2-stroke outboard engines are widely used across Africa for fishery. And, many motorcycle enthusiasts continue to love 2-strokes for their punchy, breathtaking feeling of acceleration.
 As for 4-stroke engines, they run on gasoline without any oil mixed in and the piston goes up and down two times for every combustion cycle, hence it’s called a “4-stroke.” However, 4-stroke engines require valves for both the intake and exhaust that must operate with high precision, making this engine format more complex, heavier and other disadvantages. But they provide stable power delivery, good fuel efficiency, cleaner emissions and more. This is why almost all two-wheelers, from big motorcycles to small scooters, use 4-stroke engines.

 

Difference between 4 stroke and 2 stroke engine

 

 

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