Two-Stroke vs. Four-Stroke Engines: Which Is Better for Your Needs?

2-Stroke and 4-Stroke engines are two of the most common engines you’ll find on many large applications. However, smaller applications also use them. While their usefulness cannot be over-emphasized, some people are often caught between which to choose, which is better or perhaps serves their needs.

Generally, the best way to figure this out is to first understand the engines and their mode of operation. So before we answer the question, 2 stroke vs 4 stroke which is better, let’s first see what they are, including applications they are best suited for.

2 stroke engine

2-stroke engines typically take two strokes or stages to complete a cycle. One stroke is when the piston goes from the top centre to the bottom of the cylinder. So it takes this engine going through this phase twice to produce power.

Or better explained, a 2-cycle engine completes a combustion cycle (intake, compressing, igniting, combustion and emission) twice to output energy. Power production is usually fast because it takes just two revolutions to complete a power cycle.

You will mostly find them on powerful outdoor applications such as chainsaws, trimmers, blowers etc. Two-cycle engines can also be found on smaller applications like dirt bikes, motorcycles, etc.

Pros and cons of 2-stroke engine

Just like most things out there, nothing is perfect. A 2-cycle engine has its highs and lows, let’s take a look.

Pros

The advantages of a 2-stroke engine include;

Less weight and space: Two-stroke engines utilize a design that requires the use of few components. This invariably makes it weigh less and occupy smaller space compared to a four-stroke engine.

Simple design: A two-stroke engine has a relatively simple design as its mode of operation is simply straightforward. It doesn’t use additional components like valves or cams; rather, they use ports. Their simple design also makes them easy to repair.

High RPMs: Because of fewer moving parts, a two-cycle engine can run higher RPMs compared to a four-stroke engine.

Increased efficiency: Friction is reduced during operation which invariably increases mechanical efficiency.

Versatile: The engine can work well under any temperature—cold or hot.

Fast power production: The engine features inlet and exhaust ports which makes it easier for air and emissions to enter and leave respectively. This ultimately makes power generation faster.

Cons

Having highlighted the pros, what are the disadvantages of a 2-stroke engine?

Low fuel efficiency: Fuel consumption is faster in a two-stroke engine as it consumes fuel after every two strokes. This makes it consume more fuel than a 4-stroke engine.

High emissions: A 2-stroke engine utilizes a mixture of fuel and oil which doesn’t burn completely, hence, leading to a higher pollution rate.

Loud harsh sound: Combustion in a two-stroke engine occurs very fast during each stroke, causing higher pressure waves to travel through the engine and exhaust. This invariably results in more noise and vibration during operation.

Not durable: Because 2-stroke engines are built to run at higher RPMs, the engine is susceptible to wear and tear and therefore has a shorter lifespan.

Rough idling: 2-stroke engines experience intense vibration during operation and hence may be unstable when idling.

Low-speed range: Even at optimal performance, the engine has a lower-speed range compared to 4-speed.

4-Stroke engine

Four-stroke engines go through four stages or revolutions to complete a cycle. Unlike two-stroke engines, they go through the combustion cycle (intake, compressing, igniting, combustion and emission) four times to output power. Because it goes through longer strokes, a 4-cycle engine will take a longer time to start compared to a 2-cycle engine.

4-stroke engines are more versatile and you will find them in a range of powerful applications and vehicles. This includes the lawnmower, the most common application fitted with a 4-stroke engine. Others include Cat C18 engines, 7cc RC engines, etc.

Pros and cons of 4-stroke engine

Here are the highs and lows of a 4-stroke engine

Pros

The following are the advantages of a 4-stroke engine.

Higher torque: Produces higher torque even at lower RPM compared to two-stroke engines.

Better fuel economy: A four-stroke engine uses fuel once every four strokes, hence consuming less fuel than a 2-stroke engine.

Eco-friendly: A 4-stroke engine produces less emissions since the engine does not require a mixture of oil and fuel.

Quieter operation: During operation, a four-stroke engine Produces less noise and vibration because of its slower rate of operation.

Durable: A 4-stroke engine can take a higher amount of wear and tear and, hence, has a longer lifespan than 2-stroke engines. So if you’re wondering, which is more reliable, 2 or 4-stroke? You have your answer. 

Cons

Having explored its pros, here are the disadvantages of a 4-stroke engine.

Heavier: Four-stroke engine design requires the use of more parts such as the use of a valve mechanism which invariably increases its weight.

Less powerful: Power generation is usually slower since the engine only produces energy after every four strokes, making the engine less powerful compared to a two-stroke engine.

Expensive maintenance: Four-stroke engines use more components. The use of more parts makes repair complicated which invariably increases maintenance and repair costs.

Complications during repairs: Complications can arise during maintenance since a four-stroke engine utilizes more parts such as gears and chain mechanisms.

High maintenance cost: A four-stroke design requires regular maintenance which invariably increases the cost of service.

Difference between 2-stroke and 4-stroke engines

The major difference between a 2-stroke and a 4-stroke engine is the mode of operation which typically influences how fast power is released. A 2-stroke engine completes each power cycle with one crankshaft revolution resulting in immediate release of power. Four-stroke engines on the other hand complete each power cycle with two crankshaft revolutions.

Aside from the mode of operation, the fastest way to differentiate a 2-stroke from a 4-stroke engine is to look at the fuel tank. If there is oil in the gasoline, what you have there is a 2-stroke engine; these engines run on a mixture of gasoline and oil.

A 4-stroke engine however does not need a mixture of oil and gasoline and therefore has separate tanks for gasoline and oil.

Another way to differentiate a 2-stroke from 4-stroke engine is to look for valves. Unlike 4-stroke engines, 2-stroke engines do not use valves or cams, instead they have ports.

Again the carburetor/intake manifold on a 2-stroke engine is positioned at the lower end of the cylinder whereas in a 4-stroke, they are located at the higher part and head of the cylinder.

You can also look for labeling stickers on the engine. On a four-stroke engine, you will see the description “No fuel mixing or Four stroke”. Another way of differentiating both is to look at the exhaust manifold. A wet or oil carbon deposit indicates a 2-stroke engine while a dry carbon deposit indicates a 4-stroke engine.

Or realistically, you might not need to differentiate anymore as most engines used today are four strokes. 2 cycle engines have become almost non-existent. However, here is a quick view of the differences between a 2 and 4-stroke engine.

2-stroke vs 4-stroke, which is better?

Having walked you through both engines and their pros and cons, it’s easier to decide which is better. Now to answer the question, which is better, a two-stroke or four-stroke engine? Realistically, one cannot give a straightforward answer as to which is better.

Which engine is better is subjective as it depends on what you want from the engine and your application. For example, since 2-stroke outputs power faster, they are more suited for racing applications. However, if you want something more durable with a more stable power output, a 4-stroke engine is your go-to option. 

Final words

This article has provided an answer to the question, 2 stroke vs 4 stroke, which is better. The best way to know is to look at the 2 stroke vs 4 stroke pros and cons and consider your application.

But generally, a 2 stroke engine is perfect for high-performance applications as they output power faster. However, if you own an application that needs a more steady rather than fast output and durability, then a 4-stroke engine is just perfect for you.