The internal combustion engine has been with us for over 100 years now if you can believe that. While the basic operating principles are essentially the same, developments have been achieved, and improved designs created. Of the gasoline powered variety, 2 main variants have emerged in the form of the 2-stroke, and 4-stroke engines. For most people, that doesn’t really mean anything, isn’t a stroke something that people have? We’ll get into the differences so you can understand what this is all about.
2-Stroke Vs 4-Stroke
What Is A Stroke?
Let’s start by defining what we mean by “stroke”. A stroke refers to the movement of the piston during the combustion cycle. The combustion cycle is the process whereby fuel is injected into the cylinder, compressed, ignited, and then the exhaust expelled. Continuous rise and repeat is ultimately how the engine runs. Each step in the combustion cycle is an important part of the engine’s operation.
Intake: The intake valve opens, and the exhaust valve closes while the piston moves down the cylinder, drawing a mixture of air and fuel into the cylinder.
Compression: The intake valve closes and the piston moves back up the cylinder, compressing the air-fuel mixture.
Combustion: The spark plug sparks, igniting the compressed air-fuel mixture which propels the piston down. This is where the energy for engine operation is created.
Exhaust: As the piston moves around and back up, the exhaust valve opens, allowing the gas in the cylinder to be pushed up and out of the engine.
At the end of the day, a 4-stroke engine completes each of these steps one at a time, coming out to, you might have guessed, 4-strokes. From that we can easily tell that a 2-stroke engine completes the compression cycle in two strokes, doubling up in the specific steps.
Which Is Better?
Let’s take a look at some pros and cons of each type. 4-strokes are a lot more efficient then their 2-stroke cousins in that they only burn fuel every 4 strokes. 2-strokes are designed to generally run at a higher RPM and produce more power, but that results in them wearing out faster and requiring more maintenance. Fueling up a 4-stroke is as simple as putting gasoline in the tank and starting up, with 2-strokes you need to mix oil with gas first or you run the risk of the motor seizing up. 4’s are also a more complicated design and end up being harder to work on, 2’s being simpler to easier to work with.
2’s are the ideal choice for smaller motors like lawn mowers, leaf blowers, outboard boat motors, etc. 4’s are used in large equipment like cars, trucks, inboard motors, etc, although 4-strokes are also being used in smaller applications more and more often.
Ultimately which engine is better depends on what application you intend to use it for, and which system you prefer.