Two-Strokes vs. Four-Stroke Engines: Which One Should You Buy?


In go-kart racing, two different engine types are used, 2-stroke and 4-stroke engines. Each engine has its advantages and disadvantages. In this article, I will explain how each engine works, its pros and cons, and which engine is better depending on the use.

What Is A Stroke?

All internal combustion engines contain something called an engine stroke. An engine stroke (also called a power cycle) is an internal combustion cycle sequence of events when fuel is injected into the cylinder, followed by compression, ignition, expansion, exhaust, and intake.

The main difference between these two engines is in applying the strokes, so let’s talk about how each engine works before comparing them in detail, so you can decide which type of engine suits you better.

How Two-Stroke Engines Work

The 2-strokes are smaller and less complex, with a greater power-to-weight ratio than their bigger brothers, 4-stroke. They are mainly used in sprint racing and require less maintenance. 

The way the 2-stroke engine works is as follows:

  • Intake/Compression – The burned gases from the previous cycle go out through the exhaust valve. The compressed air from the cylinder moves into the upper chamber (above the piston) from the upper intake valve. The piston then compresses the fresh air.
  • Combustor/Exhaust – A plug creates a small explosion pushing the piston down. The burned gases are then expelled through an exhaust port.

Pros of a 2-Stroke Engine

  • A two-stroke engine is a smaller and lighter engine.
  • The engine’s turning motion is even, requiring one power stroke for every crankshaft rotation.
  • Because there is no mechanical valve mechanism, these engines’ designs are relatively simple.
  • This engine generates less friction on its components during operation and has improved mechanical efficiency.
  • This engine has a significant power boost with an extremely high power-to-weight ratio, creating extra torque and responsive power.

Cons of a 2-Stroke Engine

  • Two-stroke engines consume more fuel, and only a small amount of fresh charges mix with gasses from the exhaust.
  • You may experience a high amount of vibration or noise during operation.
  • It has a shorter life span.
  • Two-strokes have a narrow power band or range within which they’re most efficient.
  • It may become unstable when idling.
  • Releases more exhaust gases and pollutants than four-stroke engines.

How Four-Stroke Engines Work

The 4-stroke engines are robust, complex, and high-maintenance, built to perform during long races. They are more efficient and will last longer than 2-stroke engines.

The way the 4-stroke engine works is as follows:

  • Intake – When the inlet valve opens, a mixture of air and fuel comes in from the inlet port, pushing the piston down. 
  • Compression – When both inlet and exhaust valves close, the piston pushes up and compresses the mixture of fuel and air which enters the combustion chamber in 1st stroke.
  • Combustion and Power Stroke – A spark plug produces an explosion that pushes down the piston.
  • Exhaust – The exhaust valve is opened, and the piston moves back up. The gas exits the chamber, and the new cycle begins.

Pros of a 4-Stroke Engine

  • Four-stroke engines produce higher torque at lower speeds than two-stroke engines.
  • Offers better fuel efficiency.
  • Produce less pollution due to advanced combustion efficiency.
  • Durable and can handle high levels of use.
  • With the four-stroke engine, you won’t need any extra oil.
  • Produces less noise and vibration than two-cycle engines.

Cons of a 4-Stroke Engine

  • Larger and heavier compared to the two-stroke engine.
  • A larger engine contains more parts, and repairs and maintenance are more complicated and expensive.
  • Because it only gets fuel once every four revolutions of the piston, it’s less powerful than a similar two-stroke engine.
  • This engine design has a complicated gearing system, which makes it difficult to maintain.
  • Regular maintenance is required, increasing the costs of parts and services.

Differences Between 2-Stroke & 4-Stroke Engines

To summarize the difference between the two types of engines, let us compare them side by side in each of the following categories: weight, durability, power, maintenance, and environment. 

Weight

The difference in weight between 2-stoke and 4-stroke engines is significant due to the size and parts that make up these two engines. While the 2-stroke is relatively simple and contains only a few parts, 4-stroke can get quite complex and have twice as many parts, adding to the weight. Because of the extra weight, 4-stroke is not great for short, sprint races, but it will outperform 2-stroke if the race is long. 

Race Durability

If maintained properly, a four-stroke engine will outlast a two-stroke engine because the combustion inside a 4-stroke engine is not as strong, thus putting less pressure on the engine components. 

Power

For an untrained eye, it is easy to confuse power with the number of strokes. The truth is that even the basic two-stroke engine creates more power than a four-stroke engine, delivering that power to the wheels quicker. This is one of the reasons why dirt bikes and motorcycles use 2-stroke engines. 

Maintenance

Maintaining a 4-stroke engine can get quite complex and if you are not a mechanic or don’t know your way around engines, make sure you go with the 2-stroke. Additionally, the complexity of the engine correlates with the parts needed for it to work properly. The more parts you need, the more money you will spend on maintenance. 

Environment

You would think that because a 2-stroke engine had stronger combustion, it is more environmentally friendly, but that is not the case. The 4-stroke engine is by far more efficient and uses far less fuel. So, if you want to help the environment by reducing exhaust gases while still enjoying racing, make sure you go with the 4-stroke engine. 

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