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Increasingly strict regulations from the European Union have encouraged vehicle manufacturers to produce smaller and smaller engines in order to comply with homologation standards. The most common strategy has been the use of three-cylinder engines, which are completely replacing the classic “inline 4-cylinder” engines.
However, engine miniaturization brings a series of advantages as well as drawbacks. In this article, we will discuss all the pros and cons of this type of engine, which is increasingly present in the automotive fleet:
Main advantages of 3-cylinder engines
Do 3-cylinder engines have any kind of advantage? Believe it or not, they do. They are as follows:
Lower fuel consumption
Having fewer cylinders and moving parts reduces internal friction, which translates into lower fuel expenditure. In addition, less energy is wasted in the form of heat. This is the main reason why manufacturers have decided to use this type of engine.
Optimized pollutant emissions
That lower friction mentioned in the previous paragraph allows the vehicle to use less fuel, and therefore, fewer exhaust gases harmful to the environment are generated. Thus, strict anti-pollution regulations are better met. Or at least, they make it easier to pass emission tests.
Lower production costs
Simplifying parts and manufacturing processes through a three-cylinder motorization reduces expenses for the assembler. We could say this translates into a lower price for the final buyer, but… looking at the current market, we’ll skip that thought. In short, this point also benefits the manufacturer quite a bit, since they can offer a specification sheet similar to the one they provided when producing four-cylinder engines, but at a lower cost.
Better space utilization
The shorter length frees up useful capacity in the engine compartment, benefiting designers and technicians. This is interesting for making room to place the turbo, or even to install auxiliary systems.
Lower maintenance cost
Fewer spark plugs, less oil… Although 3-cylinder engines are not necessarily superior in reliability—nor do they have more economical maintenance per se—it is true that we can perform somewhat more economical routine maintenance by having smaller blocks.
Disadvantages of 3-cylinder engines
Knowing that even in the advantages section we dropped a few negative points, it won’t surprise you to learn that this type of engine has a good collection of disadvantages. They are as follows:
Higher vibrations
If diesel engines seemed rough to you in terms of vibrations, three-cylinder engines won’t disappoint you in this aspect either. Four-cylinder engines self-balance because they have a “symmetrical” design. At the same time that two pistons go up, the other two go down. Three-cylinder engines cannot do that, since we will never have two cylinders performing the same stroke at the same time. And that makes the car vibrate more.
Higher noise
A direct consequence of the vibration itself. Vibrations that are not dampened translate into noise. If the car is not well insulated, we will have a vehicle that is excessively noisy, especially when driving on the highway at high speeds of 100 or 120 kilometers per hour.
Shorter lifespan
If three do the work of four, those three are subjected to higher stress. And it is an open secret that this type of engine is not expected to reach the high durability of a conventional four-cylinder, no matter how much manufacturers tell us there are no differences regarding lifespan.
If you want your three-cylinder engine to last, you will have to pamper it and service it more frequently. This point is also great for manufacturers, as it allows them to make more money with their official repair shops.
Limited performance
Historically, many utility vehicles and city cars have mounted 3-cylinder engines. They were never criticized regarding performance because these are not exactly cars where power matters. However, this is indeed a problem when they try to sell us compact vehicles and even sedans and SUVs of considerable size with this type of engine.
To compensate for the lack of muscle, almost all three-cylinder engines sold today come with a turbocharger. However, we cannot say that this element fully compensates for the lack of power, since the turbo never acts when we are moving at low revolutions, which is when we will notice the most that we have a vehicle that does not respond like the old ones.
Higher consumption under stress conditions
Remember when we said at the beginning that three-cylinder engines are great for passing homologation tests? Well, at this point we have another quite large can of worms we can open. Three-cylinder engines are designed to be low-consumption engines. However, efficiency goes out the window under maximum stress conditions, such as driving at highway speeds during a hot summer day.
Small blocks tend to overheat more than medium and large blocks. When there is excess temperature in the engine, the mixture can ignite before the spark/compression occurs, which is highly detrimental to the engine, as it can break completely. This phenomenon is known as “engine knock” or “detonation”, and manufacturers try to avoid it entirely. To do this, the only real existing solution is to inject more fuel into the cylinders to reduce the temperature. Therefore, higher consumption.
Almost all inline 3-cylinder engines sold today have this Achilles’ heel. You won’t see it reflected in the technical data sheet, nor in the WLTP cycle, obviously. Therefore, if you need a car for long road trips, our recommendation is that you forget about this type of engine. On the other hand, if you are going to make more normal use of the vehicle, they shouldn’t give you many problems.