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Two-Stroke Engine vs. Four-Stroke Engine

Have you ever heard the phrase, “The more things change, the more they stay the same.”? No matter how automobiles improve and change, the gasoline-powered combustible engine, at its core, remains the same. 

Closeup view of a v10 engine

Sure, you know your vehicle has an engine. Otherwise, you wouldn’t get very far. But do you know whether your engine is a four-stroke or two-stroke engine? 

If you’re driving a modern vehicle, it’s likely a four-stroke engine. 

What is the difference between a two-stroke and four-stroke engine, anyway? What makes one better than the other? 

In short, it depends on what the application is. In some cases, a two-stroke engine may be more beneficial than a four-stroke engine and vice versa. Learn more about each kind of engine and what makes them so different.

What Is A Stroke?

A “stroke” is the piston’s completion of a cycle during the combustion process.  

An engine’s essential job is to create combustion to generate power. During the engine’s combustion process, the piston moves up and down in the cylinder, completing a stroke. 

  • When the piston moves up, it goes to the “top dead center” (TDC) closer to the engine’s valves.
  • It is further away from the engine’s valves when it moves down to the “bottom dead center” (BDC).

What Is Combustion Revolution?

car engine cylinders

A combustion revolution is the mixing of fuel and air into the piston, ignition, and dispersal of exhaust. 

The piston moves down within the cylinder during the intake process to allow the gasoline and air mixture in the combustion chamber. Compression occurs when the piston travels back up to compress the gasses. 

Once this is complete, combustion occurs with the assistance of the spark plug to ignite the gas. Once the ignition is complete, the piston travels back up the cylinder, opening the exhaust valve to expel any exhaust left behind.  

Two-Stroke Engine vs. A Four-Stroke Engine

The difference between a two-stroke and a four-stroke engine is how quickly the combustion cycle occurs, based on the number of times the piston must travel up and down during each cycle.

What Is A Four-Stroke Engine

On a four-stroke engine, the piston completes two strokes during each cycle, which includes:

  • One stroke during compression 
  • One stroke for exhaust expulsion
  • A return stroke

The spark plugs ignite only once for every other revolution, producing power for every four strokes of the piston. 

Additionally, four-stroke engines do not demand a mixture of fuel and oil, as there is a separate area for oil. Four-stroke engines are commonly found in most cars and trucks, as well as in lawnmowers and go-karts.

What Is A Two-Stroke Engine?

With a two-stroke engine, the whole combustion process consists of one stroke of the piston: 

  • A compression stroke occurs after the ignition of the compressed fuel. 
  • On the return stroke, the exhaust expels, and the following mixture of fuel enters the cylinder. 

Additionally, the spark plugs fire only once every revolution, producing power once every two strokes of the piston. 

Smaller vehicles use two-stroke engines, such as lawn tools, boat motors, remote-controlled cars, and dirt bikes.

Significant Differences Between Two- and Four-Stroke Engines:

  • Four-stroke engines are more efficient due to less demand for fuel. Fuel is consumed once every four strokes versus two.
  • Four-stroke engines are better for the environment due to reduced emissions. A two-stroke engine releases burnt oil into the air in addition to the exhaust produced. 
  • Two-stroke engines are easier and less costly to fix due to their simple design. They possess ports instead of valves, whereas four-stroke engines have more components, which cost more to maintain or repair.
  • Two-stroke engines are much noisier than the four-stroke engine, as they produce a high-pitched whirring sound.
  • While four-stroke engines may last longer, they are not as powerful as their higher RPM two-stroke counterparts.

Engine Performance

While each engine type has its strengths and weaknesses, neither is generally superior to the other. It’s like comparing apples to oranges. 

new car engine

While the two-stroke engine has a faster cycle, it produces significant power without increasing movement. It’s ideal for high-performance off-road vehicles and lawn tools that depend on a low power-to-weight ratio. 

Four-stroke engines are best for multi-cylinder engines, such as cars, trucks, SUVs, and large vehicles. You don’t see two-stroke engines used in cars anymore due to their poor emissions. Additionally, four-stroke engines have better reliability and are easier to control.

Quality Repairs For Your Four-Stroke Engine

The next time you’re mowing your lawn, trimming your hedges, or taking a dirt bike out for some off-road adventures, you’ll understand the difference between your two-stroke and four-stroke engine and may even notice the difference in performance.

However, if you ever run into issues with your vehicle’s engine, let the Service Advisors and Technicians at Sun Devil Auto help. 

Our ASE-Certified Technicians are well-versed in everything under the hood. We offer comprehensive engine repair services for all makes and models of most cars and light trucks. 

If your check engine light is on, don’t ignore it. Bring it to your local Sun Devil Auto today for a free engine diagnosis scan.