2-Stroke VS 4-Stroke Engine | Difference between 2-Stroke and 4-Stroke (2024)

Table of Contents

Two-stroke engines and four-stroke engines are most commonly used all over the world for different applications. They are usually used in different vehicles. The main difference between a two-stroke engine and a four-stroke engine is, a two-stroke engine completes a power cycle in just two piston strokes while a four-stroke engine completes a power cycle in four piston strokes. This article mainly explains the 2-stroke engine vs the 4-stroke engine.

Difference between the 2-stroke engine and the 4-stroke engine

The two-stroke engine and four-stroke engine are different because they use different revolutions of the crankshaft and different numbers of piston strokes to complete a power cycle.

In a 2-stroke engine, all the four stages (intake, compression, power, and exhaust) of a power cycle complete in just two strokes of the piston while, in a 4-stroke engine, all the four stages (intake, compression, power, and exhaust) of a power cycle complete in four strokes of the piston.

What is a Two-Stroke Engine?

A 2-stroke engine is a reciprocating engine that uses two strokes of the piston to complete power. In this engine, intake and compression processes are completed in the first stroke of the piston, while power and exhaust processes occur in the second stroke.
It completes one revolution of the crankshaft after the completion of one power cycle.
These have low weight.

Read More: Types and Working of 2-stroke Engine

What is a Four-Stroke Engine?

A four-stroke engine is an IC engine that completes a power cycle after the completion of four-piston strokes. In this engine, intake, compression, power, and exhaust processes occur in different strokes.
This engine completes two revolutions of the crankshaft after the completion of one power cycle.
It has a quiet operation.

Read More: Working of Four-stroke Engine

2-Stroke Engine Vs 4-Stroke Engine

The main difference between a two-stroke engine and the four-stroke engine is given below:

Two Strokes	Four Stroke
This engine produces one revolution of the crankshaft after one power cycle.	This engine produces two revolutions of the crankshaft after one power cycle.
It completes a working cycle in two strokes of the piston. It generates high torque.	It completes a working cycle in four strokes of the piston. of the
The 2-stroke engine produces higher torque at a higher speed (rpm).	The 4-stroke engine produces less torque at high speed (rpm).
It can’t produce higher torque at low speeds (rpm).	This engine has the ability to produce higher torque at low speeds (rpm).
A 2-stroke engine has inlet and outlet ports for fuel suction and discharge.	A 4-stroke engine has an inlet valve and outlet valve for fuel suction and discharge.
It has low thermal efficiency.	It has high thermal efficiency.
This engine has a higher power-to-weight ratio.	This engine has a lower power-to-weight ratio.
The 2-stroke engine produces more smoke.	4-stroke engines produce less smoke.
When the oil ignites with the fuel, the engine needs more lubricating oil.	This engine needs lower lubricating oil.
It has high wear & tear issues because of poor lubrication.	These engines have lower wear & tear issues.
These engines have a low cost. Engines are cheaper and are simple for manufacturing.	These have a high cost due to extra rotating parts.
They have a simple design.	These have complex construction due to the additional parts.
These engines are not environmental-friendly.	4-stroke engines are environmental-friendly.
They have low weight and small size.	They have high weight and large size.
They produce high noise.	They have quiet operation.
A two-stroke engine needs a small space for installation.	A four-stroke engine requires a large space for installation due to its large size.
A 2-stroke engine has higher output power than a 4-stroke engine.	These engines have lower output power than two-stroke engines.
It produces more heat due to that it requires higher lubrication and cooling.	It produces less heat.
These have high heat losses.	These have lower heat losses.
They have less volumetric efficiency.	They have higher volumetric efficiency.
These engines have lower moving parts.	These have higher moving parts.
Two-stroke engines are most common in light-duty applications.	Four-stroke engines are most common in heavy-duty applications.
They are most commonly used in applications like ship propulsion, military tanks, scooters, and motorcycles.	They are most commonly used in applications like aircraft, modern bikes, motorboats, vans, buses, and trucks.

How to choose which Engine is Right for You?

The right selection of an engine for a vehicle is a very important factor for the good operation of the vehicle. When you want to select a 2-stroke engine or 4-stroke engine for your vehicle, you must keep in mind the below-given factors:

Fuel consumption: The amount of fuel consumed by an engine or other equipment is known as fuel consumption. This consumption of fuel varies according to the engine type and speed. The quantity of the fuel consumption also specifies by the manufacturer through a performance curve. Therefore, before buying any engine, you must know the type of your engine (whether a 2-stroke or 4-stroke engine) and your engine’s fuel consumption quantity and make a purchase according to your budget.
Engine efficiency: The amount of fuel energy that an engine converts into useful work is known as engine efficiency. The petrol engine has efficiency from 25% to 30%. You must look at the efficiency of the engine before buying the engine because the higher the engine efficiency, the higher will be its fuel economy.
Emissions: The emission process in an engine occurs due to unburn gases. This is also an important factor that needs to keep in mind for the selection of an engine. In the case of a 4-stroke engine and a 2-stroke engine, the 4-stroke engine emits fewer exhaust gases than the two-stroke engine.
Weight: the two-stroke engine has a lower weight than a four-stroke engine. You must choose the engine according to the capability of your vehicle. It is recommended to choose a four-stroke engine for heavy-duty vehicles like buses, trucks, airplanes, vans, etc. You must choose a 2-stroke engine if you want to use your vehicle for light-duty applications like motorcycles, bikes and vans etc.

FAQ Section

Why does oil in a 2-stroke engine need to change?

In a 2-stroke engine, the oil must be changed because this oil supports cooling the cylinder and piston by their proper lubrication. If you do not properly lubricate to cylinder and piston, the metals may melt and crush each other, metals can move past each other and deform permanently, and high friction can wear parts out and clog the engine. Therefore, it is advisable to keep changing the oil to keep the engine running properly.

Why don't we have a three-stroke engine?

In order to operate the engine, four important processes must be performed:

Intake
Compression
Power
Exhaust

In the case of the three-stroke engine, you will need to select only three strokes from the above-given strokes by leaving one stroke. Such an engine is not possible because it is impossible to produce power in four operations with three strokes.

Are 2-Stroke Engines Bad for the Environment?

The 2-stroke engine is not environmental-friendly. The reason is that these engines have ports due to that waste heat leaves the cylinder and generates emissions.

Which engine is more noisy?

A 2-stroke engine generates more noise than a 4-stroke engine.

Why 2-Stroke engine is Faster?

A 2-stroke engine completes a power cycle in just two strokes instead of 4 strokes. Therefore, it completes a power cycle faster than 4-stroke engines. 2-stroke engines also have few parts and are lightweight. A good power-to-weight ratio and high engine rpm play a vital role to enhance vehicle performance.

Give some examples of a two-stroke engine.

Two-stroke engines are used in small applications such as bikes, motorcycles, boat motors, chainsaws, lawn tools, and remote-controlled cars.

Less wear and tear occurs in which type of engine?

In the 4-stroke engine, less wear and tear occurs.

Working of Two-stroke Engine
Working of Four-stroke Engine
Types of Engines
Different types of IC Engines