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What is the Difference between a Two-Stroke and a Four-Stroke Engine?

If you own a car, motorcycle, or any other type of vehicle, you must have come across the terms "2- stroke or 4- stroke combustion engine" at one time or another. Here, we have compiled the differences between the two to help you understand the basic working.

Understanding Combustion Engines

The engines in our vehicles are referred to as "internal combustion engines" because they produce power by the combustion process. Each combustion cycle takes place inside the cylinders and depends upon the upward and downward "strokes" of pistons. It comprises of following steps:

  • Intake of air and fuel- pistons move downward to allow the air and gas/fuel to enter while the intake valve is open.
  • Compression of gases- intake valve closes and pistons move up to compress the air, fuel mixture.
  • Combustion of gases- spark plug ignites the compressed gases to produce a burst of power.
  • Exhaust of waste fumes- with the exhaust valve opened, the piston moves up to remove the combustion by-products.

2-Stroke VS 4-Stroke engines

As is evident from the names, the main difference between the two engine types is based upon the pistons' movements.

In a 4-stroke engine, the whole combustion cycle is completed in 4 strokes of the piston; a downward movement to let the air in, an upward stroke to compress the gases, down movement as a power stroke due to ignition and combustion of gases, and the last upward exhaust motion. In contrast, a 2- stroke engine completes the combustion cycle in just one piston revolution or 2- strokes; upward and downward.

Other differences between the two types of engines include:

  • the spark plug ignites at every revolution in a 2-stroke engine, whereas it does so every other revolution in a 4-stroke engine.
  • 4-stroke engines have a separate compartment for oil, in contrast to a 2-stroke engine that uses a mixture of oil and fuel for ignition.
  • 4-stroke engines are quieter and more efficient. Alternatively, 2- stroke engines are noisy but lighter and cheaper.

Applications

4-stroke engines, being more reliable, are used in cars, buses, trucks, and other vehicles. 2-stroke engines are commonly found in smaller appliances and vehicles such as motorcycles etc. No matter what is the type of engine, it requires regular maintenance. If you find yourself in need of engine repair, visit our auto repair shop to get exceptional services.