1.5L 3-cylinder Dragon engine of the Ford Bronco Sport.
A 3-cylinder engine is a type of internal combustion engine that has three cylinders arranged in-line. With stricter fuel economy and emission standards, more auto makers equip their cars, crossovers and even small SUVs with 3-cylinder engines. What are the pros and cons of a 3-cylinder engine compared to a conventional 4-cylinder motor?
Fuel Efficiency. The 3-cylinder engine is lighter and has fewer moving parts, which means less friction. This makes a 3-cylinder engine more fuel efficient than a similar 4-cylinder engine.
Lower Emissions. For the reasons described above, 3-cylinder engines tend to produce less emissions than 4-cylinder engines, making them more environmentally friendly.
Cheaper to produce. Compared to similar 4-cylinder engines, 3-cylinder engines have fewer parts and use less metal. This makes the manufacturing process cheaper.
More space under the hood. Since a 3-cylinder engine is shorter than a 4-cylinder engine, there is more space under the hood. This allows car designers more flexibility. It also makes a 3-cylinder engine more accessible and easier to work on.
Cheaper to replace spark plugs. Since there is one fewer spark plug to replace, this maintenance task will cost less than in a 4-cylinder engine.
Inherent vibration. In a 4-cylinder engine, there is a natural balance as 2 pistons are going up and two pistons are going down. 3-cylinder engines are more difficult to balance which means extra measures must be taken to reduce vibration inherent to the design. That said, we test drove several modern cars with a 3-cylinder engine and the difference in vibration is barely noticeable.
3-cylinder engines are typically louder than 4- or 6-cylinder engines. One reason is that 4- or 6-cylinder engines are heavier and have more oil and coolant and as a result, absorb the noise better.
3-cylinder engines are less likely to last for as long as comparable 4-cylinder engines. This is because 3 pistons have to work harder than 4 pistons in a 4-cylinder engine.
Limited power. The 3-cylinder engine is a smaller engine with limited power.
Considering the previous point, most 3-cylinder powered cars require a turbocharger in order to deliver necessary power when accelerating or merging. The turbocharger adds complexity. Many 4-cylinder cars don't have turbochargers, as a 4-cylinder engine can deliver more power without a turbocharger.
Why are 3-cylinder engines more noisy?
Sound of a 3-cylinder 1.5L engine. Ford Bronco Sport
4-cylinder engines are naturally 'balanced' since when two pistons are moving up, two other pistons are moving down. In 3-cylinder engines, one piston moves up at a time. This creates more vibration. 3-cylinder engines are also smaller and lighter. This means there is less metal as well as less oil and cooling fluid to absorb the noise. The video shows the 1.5L 3-cylinder engine of the 2021 Ford Bronco Sport.
What is the life of a 3-cylinder engine?
1.3L 3-cylinder engine of the Chevrolet Trailblazer.
At the moment, there are not that many modern 3-cylinder cars to be able to see how long they last, but we can estimate. We know that a good 4-cylinder engine can easily last for over 200,000 miles. This means a good 3-cylinder engine should last for at least 170-180K miles with good care.
The difference is that a smaller 3-cylinder engine has to work harder to accelerate the vehicle compared to a 4-cylinder engine. That's why some V8s, for example, last for over 500,000 miles.