3-cylinder engine vibration, noise, and reliability: Still a problem?

Arif · Jan 24, 2021 10:45 AM

3-cylinder engine vibration, noise, and reliability: Still a problem? 01

In the recent years, we have welcomed some new three-cylinder engine cars to the world – the Nissan Almera 1.0 turbo, Honda City 1.0 turbo (Thailand), Proton X50, and more excitingly, the Toyota GR Yaris.

3-cylinder engine vibration, noise, and reliability: Still a problem? 02

Even Christian von Koenigsegg has channelled his genius into developing a 600 HP three-cylinder engine. With these developments however, some of us still remain very sceptical of them.

3-cylinder engine vibration, noise, and reliability: Still a problem? 03

We will never forget the underpowered three pots in tiny cars like the Perodua Kancil and Perodua Kelisa. Sure, they were economical, but boy you would never forget how hard the engines shook the whole car. 

3-cylinder engine vibration, noise, and reliability: Still a problem? 01

Legend. Photo: housedoktor

Have things improved over the years for three-cylinder engines when comes to vibration and noise?

Vibration

3-cylinder engine vibration, noise, and reliability: Still a problem? 02

The core problem with three-cylinder engines is the uneven number of cylinders. It’s not so easy to cancel out the forces. Five-cylinder engines have the same problem too (or try one-cylinder). 

3-cylinder engine vibration, noise, and reliability: Still a problem? 03

3-cylinder (red) vibrates more than 4-cylinder (blue). The gap closes at higher RPM. (Research by Honda)

Over the years, many solutions have been shown to help reduce this imbalance. Obvious ones are counterweighted crankshafts and balancing shafts.

And then there are further measure that can be taken like reducing the weight of reciprocating parts (e.g., Honda 1.0 turbo) and asymmetrical oil pump impellers (e.g., Proton 3-cylinder).

3-cylinder engine vibration, noise, and reliability: Still a problem? 04

The Thai-spec Honda City 1.0 Turbo's crankshaft is smaller and lighter. (to reduce weight of reciprocating parts)

However, it's still hard for a 3-cylinder to beat the naturally cancelled out forces of an even-numbered-cylinder engine. Look at the graph above and you will see that the three-cylinder still vibrates more.

What manufacturers can do to reduce feelings of vibration in the cabin are improved engine mounts and chassis design.

Noise

3-cylinder engine vibration, noise, and reliability: Still a problem? 05

Noise level against engine speed. 3-cylinder engine is red, 4-cylinder engine is blue

At low rpms, three cylinder engines can be louder than 4-cylinder engines. The difference becomes less obvious at higher rpms. That's what research from Honda shows on its new 1.0-litre turbo engine.

Although we must say from our experience with three-cylinder engines, the noise inside the cabin is not much different than a four banger since sound insulation materials play a big part too.

We test the noise levels of all the cars we review at 0 km/h (with AC on and off), 60 km/h, 90 km/h, and 110 km/h. Here’s what the numbers look like:

Cabin Noise Levels (dB)
  2020 Honda City 1.5 V 2019 Proton Persona 1.6  2020 Nissan Almera 1.0 VLT
0km/h (AC off) 39 42 38
0 km/h (AC on) 46 47 46
60 km/h 65 63 62
90 km/h 68 66 66
110 km/h 70 70 68

In the case of the 3-cylinder Nissan Almera, its can even be quieter than its 4-cylinder rivals. (Of course, sound insulation plays a big part here)

Reliability

There is absolutely no reason for a three-cylinder engine to be less reliable than a four-cylinder engine if both are built with the same material and build quality.

3-cylinder engine vibration, noise, and reliability: Still a problem? 06

Reliability issues of three-cylinder engines stem from the fact that they were usually “budget” products. Hence engine architecture could have been optimised to reduce cost and lower grade materials could be used too.

With tighter emission rules these days, three-cylinder engines are no longer “budget” products. They have become the norm and some have even become premium products.

3-cylinder engine vibration, noise, and reliability: Still a problem? 07

The three-cylinder engine in a Perodua Kancil, Nissan Almera, Proton X50, Toyota GR Yaris, and Koenigsegg Gemera are built on totally different budgets and that greatly affects the quality and reliability.

Have there been terrible 3-cylinder engines?

Well yes definitely. Some car models have even returned to 4-cylinder engines from 3-cylinder engines because they didn't turn out as well as planned. Case in point, the GAC GS3 that switched to three cylinders in 2019 and reverted to four cylinders in 2020.

As for the issue of engine mount wear, it relates closely to the vibrational forces of engine. We do not deny that poorly balanced engines will wear out engine mounts faster. 

Summary

3-cylinder engine vibration, noise, and reliability: Still a problem? 08

The main issue with 3-cylinder engines is vibration, and various developments have been made to reduce it. In terms of noise levels, three-cylinder engines are comparable to the standard four-cylinder. They just sound different. And when it comes to reliability, three-cylinder engines are no longer just “budget” products. Sure, some three cylinders are inferior, but they are not all made the same.
 

Arif

Writer

Previously an engineer in an automotive manufacturing company and a highway concessionaire. A part-time research student on biofuels and diesel engines. Obsessed with vehicle electrification and the future of transportation.

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