Difference Between Two-Stroke And Four-Stroke

The key difference between two-stroke and four-stroke is that a 4-stroke engine completes one power stroke in four stages, which corresponds to two full revolutions of its crankshaft, whereas a 2-stroke engine accomplishes a power stroke in two stages, equivalent to one complete revolution of its crankshaft.

What is Two Stroke?

In a 2-stroke engine, the entire combustion process occurs within a single piston stroke. This includes compression, ignition of the compressed fuel, exhaust expulsion during the return stroke, and intake of a fresh fuel-air mixture.

The spark plugs ignite once per revolution, generating power every two piston strokes. Additionally, 2-stroke engines necessitate mixing oil with the fuel in advance.

What is Four Stroke?

In a 4-stroke engine, the piston performs two strokes in a single revolution: a compression stroke and an exhaust stroke, followed by a return stroke.

The spark plugs ignite the fuel-air mixture once every two revolutions, resulting in power generation occurring every four piston strokes. These engines have a dedicated oil compartment, eliminating the need for mixing fuel and oil beforehand.

Two Stroke Vs Four Stroke

The primary difference between two stroke and four stroke is given below:

AspectTwo StrokesFour Strokes
Crankshaft Revolutions per Power StrokeOneTwo
Torque GenerationHighLess
Fuel Inlet/OutletPortValves
Thermal EfficiencyLesserHigher
Power-to-Weight RatioLargerLesser
Smoke Generation and EfficiencyMore smoke, less efficiencyLess smoke, more efficiency
Lubricating Oil RequirementMoreLess
Wear and TearMore due to poor lubricationLess
Manufacturing CostCheaper and simplerExpensive due to lubrication and valves
Weight and NoiseLighter and noisierHeavier with a heavy flywheel, less noisy

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