Difference Between 2-Stroke and 4-Stroke Engines

April 30, 2022

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Automotive engines have transformed over the years, but two main petrol powered combustion engine designs remain the same over the decades – the 2-stroke and the 4-stroke. While we’re sure you’ve at least heard these terms before, do you really know the difference between them? How do they work, and which is better? Read on to learn about the difference between 2-stroke and 4-stroke engines.

What is a 2-Stroke Engine?

In such a type of engine, the entire combustion cycle is completed with only one piston stroke. It consists of a compression stroke followed by the explosion of the compressed fuel. Then after the return stroke, the exhaust is let out and hence a fresh fuel mixture moves into the cylinder. The spark plugs fire once in every single revolution, and therefore power is produced once in every 2-strokes of the piston. It is to be noted that such engines require the oil to be pre-mixed in with the fuel.

Working of 2-Stroke Engine

What is a 4-Stroke Engine?

In such a type of engine, the piston completes its two-strokes during each revolution. It consists of one compression stroke and then one exhaust stroke, afterward each will have a return stroke. The spark plugs fire only once during one next revolution. Therefore the power is produced in every four-strokes of the piston. It is to be noted that there is no requirement pre-mixing of fuel and oil. This is because they have a separate compartment for the oil.

Working of 4-Stroke Engine

The important difference between 2-stroke and 4-stroke engines:

Parameter	2-Stroke	4-Stroke
Inlet and Outlet	It is using the port for fuel’s outlet and inlet.	It is using valves for the outlet and inlet of a fuel.
Torque	It creates high torque.	It creates less torque.
Number of Revolutions	The number of revolutions of the crankshaft during one power stroke is one.	The number of revolutions of the crankshaft during one power stroke is two.
Thermal Efficiency	These engines are having lesser thermal efficiency.	These engines are having higher thermal efficiency.
Weight and Noise Level	These engines are lighter but noisy.	These engines are heavier due to its flywheel but are less noisy.
Power to Weight Ratio	The power to weight ratio is larger.	The power to weight ratio is lesser.
Cost Factor	These are cheaper due to a simple manufacturing process.	These are expensive due to the tough manufacturing of lubrication and valves.
Smoke Level	It generates more smoke with less efficiency.	It generates less smoke with more efficiency.
Need of Oiling	It needs more lubricating oil due to oil burning with the fuel.	It needs less lubricating oil.
Wear and Tear Factor	More wear and tear due to poor lubrication.	Less wear and tear.
Examples	Outdoor power equipment such as chainsaws, blowers, trimmers and hedge trimmers use a two-stroke motor. You can also use a two-stroke engine in transportation and equipment devices such as outboard motors, motorcycles or dirt bikes.	Four-stroke engines are found in anything from go-karts, lawnmowers and dirt bikes, right up to the typical internal combustion engine in your vehicle.