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Chapter: Mechanical Engineering : Internal Combustion Engines

Comparison Between Four Stroke Cycle And Two Stroke Cycle Engine (Merits And Demerits)

Merits And Demerits - Different Between Four Stroke Cycle And Two Stroke Cycle Engine

COMPARISON BETWEEN FOUR STROKE CYCLE AND TWO STROKE CYCLE ENGINE (MERITS AND DEMERITS):

 


 

Two Stroke Cycle Engine

 

Merits:   One   power   stroke   in   one revolution of the crankshaft

 

Power  developed  for  the  same  engine speed  theoretically  twice  that  of  a  four stroke engine

 

Simple design and lighter in construction for the same power

 

Merits: Uniform torque is obtained. Hence a lighter fly wheel can be used

 

Design  of  ports  is  simpler.  Hence  initial cost is less

 

Mechanical efficiency is high. No moving parts like cam, follower, rocker arm valves etc.,

 

Merits: Starting is easy

 

These engines are generally air cooled

 

Four Stroke Cycle Engine

 

Demerits:  One  power  stroke  in  two revolutions of the crank shaft

 

Power  developed  for  the  same  engine  speed  is  theoretically  half  that  of  two stroke engine.

 

For the same power complicated design and heavier in construction

 

Demerits:  Non  uniform  torque  on  the crankshaft.  Hence  a  heavier  flywheel  is required for balancing.

 

Design  valve  mechanism  is  difficult.  Hence initial cost is more.

 

Mechanical  efficiency  is  less.  Power  is lost  due  to  friction  caused  by  valve mechanism

 

Demerits: Starting is not so easy

 

These engines are generally water cooled.

 

 

COMPARISON BETWEEN FOUR STROKE CYCLE AND TWO STROKE CYCLE ENGINE (MERITS AND DEMERITS):

 


 

Two Stroke Cycle Engine

 

DeMerits: Consumption of lubricating oil is more, because less time is available to remove the heat

 

More wear and tear of moving parts.

 

Some of the fresh air fuel mixture may escape with exhaust gases. Hence fuel consumption is more

 

DeMerits: Thermal efficiency is less.

 

It produces more noise due to sudden release of exhaust gases

 

Scavenging is poor, since exhaust port is open only for a short time

 

Merits: Poor scavenging leads to mixing of fresh charge with exhaust gases. This results in poor performance, slow running

 

Used in light vehicles, like bikes, scooters, mopeds, etc.

 

Four Stroke Cycle Engine

 

Merits: Consumption of lubricating oil is less, because more time is allowed for removing heat from the cylinder.

 

Less wear and tear of parts is less

 

Fuel cannot escape with exhaust gases. Hence fuel consumption is less.

 

Merits: Thermal efficiency is more.

 

Noise is less is less. Exhaust gases are released in separate stroke.

 

Scavenging is better, since there is a separate exhaust stroke for the removal of exhaust gases

 

Demerits: Better performance and efficiency is more

 

 

Used in heavy vehicles, like buses, lorries, trucks etc.

 

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Mechanical Engineering : Internal Combustion Engines : Comparison Between Four Stroke Cycle And Two Stroke Cycle Engine (Merits And Demerits) |


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