Which one is more efficient? A four stroke engine or a two stroke and why?

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Answered by: padmaja

  • Oct 5th, 2006

although four stroke engine is more frequently used 2STROKE engine is more effiecient because for every 2 strokes there is a power stroke.for same power generation 2STROKE ENGINE is compact

Showing Answers 1 - 37 of 37 Answers


  • Sep 5th, 2006

Four stroke is more efficient than two stroke, because due to the factors like their effeciency, speed, milage (in practical) and fuel consumption...


  • Sep 5th, 2006

four stroke

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murali dharan

  • Sep 7th, 2006

four stroke.because in the four stroke engine ,power stroke occures two times in a cycle rotation....


  • Sep 16th, 2006

4 Stroke engine is more efficient primarly bcoz of the prescence of valves which precisely control the flow of charge into the chamber and exit the exhaust gases with proper timing which is hard to achieve by ports in a 2 stroke engine.


  • Oct 5th, 2006

although four stroke engine is more frequently used 2STROKE engine is more effiecient because for every 2 strokes there is a power stroke.for same power generation 2STROKE ENGINE is compact


  • Oct 7th, 2006

four stroke engine is eff than 2 stroke bcos @ full load & half load, the fuel consumption is effective and economical

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  • Oct 13th, 2006

2 stroke - simple google search will tell u why

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  • Oct 14th, 2006

four stroke engine is more efficient because the less wastage of gas .A power stroke is completed in two revolution of crank so more power is generated.its efficiency is also high


  • Oct 14th, 2006

4 stock engine is more eff then 2 st eng because the fule consumpiton of 4 st eng is lesser then the 2 sto eng & noise also lesser in 4 st eng

Maruthi reddy

  • Oct 16th, 2006

A 4-Stroke egine is more efficient than a 2 stroke engine.


  • Oct 23rd, 2006

Four Stroke is more efficient, based on fuel consumption, since it has to follow 4cycles.


  • Dec 4th, 2006

four stroke engine is more efficient becoz in them valves are used whereas in two stroke engine ports are used so the leaking of combusted mixtures is more in two stroke compared to four stroke .actually combusted mixtures are accounted for the power generation.so the generated power is less in two stroke engine

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  • Dec 5th, 2006

2 stroke is efficient.

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  • Jan 23rd, 2007

If you refer to efficiency in fuel, a 4 stroke engine is definitly better due to the presence of valves and because there is only one power stroke for every 4 stroke, so fuel is injected only in 1 stroke.But 2 stroke engines are used in high power applications, because it provides more number of power strokes which makes it more powerfull. Power of 2 stroke is more but efficiency of 4 stroke is higher.


  • Mar 15th, 2007

Hello padmaja

What u said is absolutely wrong. 2 stroke is not at all more efficent than 4 stroke why because more fuel is taken out by exaust gases and one more thing is its not possible to expand whole gases in power stroke due to overlapping of expansion stroke and transfer of charge into engine cylinder.

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john shafin

  • Apr 7th, 2007

first of all the question is not clear!looking from thermal efficiency side two stroke is more efficient as padmaja said..but in terms of fuel economy four stroke engine is more efficient...

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  • Jul 5th, 2007

Absolutely 4-stroke engine because scavengining losses are very less in 4-stroke engines where as incase of 2-stroke engines it is very high and one more reason is power is produced for every 2 strokes of the piston it means friction losses are high and fuel consumption is also high.

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Arun Narayanan

  • Jul 16th, 2007

The thermal efficiency of a 4-stroke is more than that of a 2-stroke.
But for same size of engine a 2-stroke produces about 1.8 times the power of 4-stroke.

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  • Aug 7th, 2007

A four stroke engine is more efficient than a 2 stroke engine because in 2 stroke because,The actual compression starts when ports are completely closed by the upward movement of the piston after few degree revolution of the crank shaft. Thus, the actual compression ratio and thermal efficiency 2 stroke engine is less than the 4 stroke engine for the same dimesions and more over there is a lot of wear and tear of moving parts

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  • Sep 6th, 2007

A four stroke engine is more efficient. bcoz here power is developed in every alternate revolutions of crankshaft. Here power developed will be more due to homogenious mixing of air fuel. But number of revolutions will be less. Incase of 2s power will be less. Revolutions will be more, low thermall efficiency and abnormal fuel combusion due to scavenging.


  • Oct 23rd, 2007

4 stroke is more efficient because of the valve, which are not in 2 stroke engines.the fuel is not wasted in 4 stroke as the valves operate in predetermined time interval and in 2 stroke the ports are always in open, which causes some unburned fuel to go out with exhaust gases..

Comparison of two stroke and four stroke engines...

2 stroke engine: in 2 stroke engine one power stroke is obtained from 2 strokes of piston or one revolution of crank shaft..

4 stroke engine: in 4 stroke engine one power stroke is obtained from 4 strokes of piston two revolution of crank shaft..

For the same speed and given size 2 stroke engine produces more power then 4 stroke engine. but due to scavenging the thermal
efficiency is more compared to 2 stroke engines.


  • Dec 11th, 2008

A two stroke engine is more efficient than four stroke.because a two stroke engine produces power in one revolution of the crankshaft whereas four stroke engine in two revolution. As a result the power developed by two stoke will be double than four stroke. but the heat developed will be more so strong cooling system should be used in case of two stroke.

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  • Dec 27th, 2008

Four stroke for efficiency, fuel consumption and mileage. 2 stroke is for speed alone.

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  • Nov 1st, 2009

When we talk about efficiency then 4-stroke is better than 2-stroke. Although for same size of engine power of 2-stroke is more b'coz in one revolution of crankshaft one power stoke is produced. For same amount of power 2-stroke is lighter but altogether taking all parameter in consideration 4-stroke is more efficient.

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  • Mar 28th, 2010

In thermal efficiency the 4 stroke is more than 2 stroke because fuel consumptiont in 2 stroke is high than 4 stroke due absence of valves (there is just a hole in 2 stoke engine). 

In mechanical power the 2 stroke engine is more efficient than 4 stroke engine because of crankshaft laps.

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A Four stroke engine is more efficient as compare to Two stroke engine, Because a Four stoke engine consumed less fuel and also wear and tear is also less due to which maintenance cost is also  less, hence life is long and most important think is, it is helpfull to saved to the petrol, but in case of two stroke engine it opposite to four stroke engine.

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  • Aug 5th, 2011

Two stroke means one rotation of shaft to complete the cycle
four stroke means two rotation of shaft to complete the cycle
better power in two stroke and better fuel efficiency in four stroke

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sanket mahadik

  • Aug 6th, 2011

4stroke engine is most efficient engine. Even the 2 stroke engine power output is more.losses of power in 2 stroke engine is also more.we cant provide better coiling system to two stroke engine.

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Although,power developed in two stroke engine is more but four stroke engines are more efficient because as in the absence of suction and exhaust stroke amt. of air inducted become less thereby mechanical and thermal efficiency of an two stroke is less where as it is more in case of 4stroke engine.another factors are use of valve mechanism.

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Pradeep sharma

  • Nov 25th, 2011

4 stroke is more efficient due 2 its better milage, less wear & tear of parts, contain valves prevent frm leakage, deliver one power stroke in 4 cyle.

But in case of power, 2 stroke is better. it delivered 1 .8 times more power than 4 stroke.

Bt overall view favoured to 4 stroke engine.

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  • Dec 19th, 2011

2 stock engine is more efficient than 4 strock, because Power generation for 2 strock required one strock of compression and one strock of discahrge, while for the same power a 4 strock engine required One strock of Intack,One strock of Compression, one strock of Expansion and one strock of discharge, So power output at the flywheel take more time in 4 strock then in 2 strock , thus consmue more fuel.

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