Difference Between 4-Stroke And 2-Stroke Engine
The fundamental difference between the four-stroke engine and the two-stroke engine is how the induction and exhaust processes take place. In the four-stroke engine, there are separate strokes for the induction and exhaust processes. In the two-stroke engine, however, both the induction and exhaust processes take place with the same stroke. The process that involves both induction and exhaust is called scavenging, or simply a gas exchange process.
Let's understand about both strokes engines.
4-Stroke Engine:
A four-stroke engine is an internal combustion engine in which the piston completes four separate strokes while turning the crankshaft.
A four-stroke engine is an internal combustion engine in which the piston completes four separate strokes while turning the crankshaft.
2-Stroke Engine:
A two-stroke engine is an engine that completes a power cycle with two strokes of the piston during only one crankshaft revolution.
A two-stroke engine is an engine that completes a power cycle with two strokes of the piston during only one crankshaft revolution.
Difference between both 4-Stroke and 2-Stroke Engines as follows
1) Revolution of Crankshaft:
4-Stroke: It has two revolutions of the crankshaft during one power stroke.
2-Stroke: It has one revolution of the crankshaft during one power stroke.
4-Stroke: It has two revolutions of the crankshaft during one power stroke.
2-Stroke: It has one revolution of the crankshaft during one power stroke.
2) Power Produce:
4-Stroke: Power produce is less.
2-Stroke: Theoretically power produce is twice that of the four-stroke engines for the same size.
4-Stroke: Power produce is less.
2-Stroke: Theoretically power produce is twice that of the four-stroke engines for the same size.
(Power to weight ratio is more in 2-Stroke Engines than 4-Stroke Engines).
3) Absence of Oil ring:
4-Stroke: Presence of Oil ring in 4-Stroke Engine.
2-Stroke: Absence of Oil ring in 2-Stroke Engine.
4-Stroke: Presence of Oil ring in 4-Stroke Engine.
2-Stroke: Absence of Oil ring in 2-Stroke Engine.
4) Valve Mechanism :
4-Stroke: Presence of Valve mechanism (inlet and exhaust valves) in 4-Stroke Engine.
2-Stroke: Absence of Valve mechanism in 2-Stroke Engine.
4-Stroke: Presence of Valve mechanism (inlet and exhaust valves) in 4-Stroke Engine.
2-Stroke: Absence of Valve mechanism in 2-Stroke Engine.
5) Construction:
4-Stroke: Construction is more complex than a 2-stroke Engine due to the presence of a Valve mechanism.
2-Stroke: construction is simple than a 4-Stroke Engine due to the absence of a valve mechanism.
4-Stroke: Construction is more complex than a 2-stroke Engine due to the presence of a Valve mechanism.
2-Stroke: construction is simple than a 4-Stroke Engine due to the absence of a valve mechanism.
6) Flywheel Size:
4-Stroke: The size of the flywheel is heavier than the 2-Stroke Engine.
2-Stroke: The size of the flywheel is lighter than the 4-Stoke Engine.
4-Stroke: The size of the flywheel is heavier than the 2-Stroke Engine.
2-Stroke: The size of the flywheel is lighter than the 4-Stoke Engine.
7) Transfer Port:
4-Stroke: Absence of transfer port
2-Stroke: Presence of transfer port.
4-Stroke: Absence of transfer port
2-Stroke: Presence of transfer port.
8) Weight:
4-Stroke: Weight is more than 2-Stroke Engine.
2-Stroke: Weight is less than 4-Stroke Engine due to fewer components used in engine construction.
4-Stroke: Weight is more than 2-Stroke Engine.
2-Stroke: Weight is less than 4-Stroke Engine due to fewer components used in engine construction.
9) Crankcase:
4-Stroke: Only engine oil is present in the crankcase of the 4-Stroke Engine.
2-Stroke: It has a premixed lubrication system and hence it contains both Engine oil and fuel in the crankcase.
4-Stroke: Only engine oil is present in the crankcase of the 4-Stroke Engine.
2-Stroke: It has a premixed lubrication system and hence it contains both Engine oil and fuel in the crankcase.
10) Fuel Efficiency:
4-Stroke: The fuel Efficiency of a 4-Stroke Engine is more than a 2-Stroke Engine because practically the consumption of fuel per rotation of the crankshaft is less in a 4-Stroke Engine.
2-Stroke: The fuel Efficiency of a 2-Stroke Engine is lower as during scavenging, both inlet and exhaust ports are open simultaneously for some time, some part of fresh charges containing fuel escapes with the exhaust.
4-Stroke: The fuel Efficiency of a 4-Stroke Engine is more than a 2-Stroke Engine because practically the consumption of fuel per rotation of the crankshaft is less in a 4-Stroke Engine.
2-Stroke: The fuel Efficiency of a 2-Stroke Engine is lower as during scavenging, both inlet and exhaust ports are open simultaneously for some time, some part of fresh charges containing fuel escapes with the exhaust.
11) Engine Performance:
4-Stroke: there are separate intake and exhaust strokes for fresh and burnt charges that make lesser issues of engine performance in 4-Stroke engine compared to 2-Stroke.
2-Stroke: Fresh air charge always mixes with exhaust which makes engine performance down.
4-Stroke: there are separate intake and exhaust strokes for fresh and burnt charges that make lesser issues of engine performance in 4-Stroke engine compared to 2-Stroke.
2-Stroke: Fresh air charge always mixes with exhaust which makes engine performance down.
12) Noise:
4-Stroke: It is much quieter due to design construction.
2-Stroke: It is significantly louder and has a distinctive, high-pitched "buzzing" sound.
4-Stroke: It is much quieter due to design construction.
2-Stroke: It is significantly louder and has a distinctive, high-pitched "buzzing" sound.
13) Thermal Efficiency:
4-Stroke: It has more thermal efficiency as it generates power in 2 revolutions of the crankshaft.
2-Stroke: It has less thermal efficiency.
4-Stroke: It has more thermal efficiency as it generates power in 2 revolutions of the crankshaft.
2-Stroke: It has less thermal efficiency.
14) Friction Loss:
4-Stroke: Friction loss is more due to more parts in engine design.
2-Stroke: Friction loss is less due to fewer parts available.
4-Stroke: Friction loss is more due to more parts in engine design.
2-Stroke: Friction loss is less due to fewer parts available.
15) Initial and Maintenance cost:
4-Stroke: Initial and maintenance costs are more as it has more parts and complex design than 2-Stroke.
2-Stroke: Initial and maintenance costs are less as they are much simpler designs, making them easier to fix.
4-Stroke: Initial and maintenance costs are more as it has more parts and complex design than 2-Stroke.
2-Stroke: Initial and maintenance costs are less as they are much simpler designs, making them easier to fix.
16) RPM:
4-Stroke: Creates higher torque at a lower RPM.
2-Stroke: Creates more torque at a higher RPM.
4-Stroke: Creates higher torque at a lower RPM.
2-Stroke: Creates more torque at a higher RPM.
17) Effect on Environment:
4-Stroke: 4-Stroke Engine is more environmentally friendly as oil and fuel do not mix.
2-Stroke: Requires pre-mixing of oil and fuel where burnt oil is also released into the air with the exhaust and makes an effect on the environment.
4-Stroke: 4-Stroke Engine is more environmentally friendly as oil and fuel do not mix.
2-Stroke: Requires pre-mixing of oil and fuel where burnt oil is also released into the air with the exhaust and makes an effect on the environment.
18) Application:
4-Stroke: Used where efficiency is important such as cars, buses, trucks, etc.
2-Stroke: 2-stroke (air-cooled) petrol engines in lawnmowers, scooters, etc. 2-stroke diesel engines are mostly used for ship propulsion.
4-Stroke: Used where efficiency is important such as cars, buses, trucks, etc.
2-Stroke: 2-stroke (air-cooled) petrol engines in lawnmowers, scooters, etc. 2-stroke diesel engines are mostly used for ship propulsion.
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