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Smaller, More Efficient Engines Work Harder; Noise Suppression More Important

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2014 Mitsubishi Mirage ES  -  Driven, April 2014

2014 Mitsubishi Mirage ES - Driven, April 2014

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For a long time in the U.S. car market, bigger was better.

From engines to bodywork, size meant luxury and performance. But recently, manufacturers and customers alike have got used to a new concept: downsizing.

In terms of engines, this means doing more with less. But engineers have encountered a new problem to deal with in smaller engines: noise, vibration and harshness (NVH).

As anyone who has driven more than a few cars in their lifetime will know, you typically need to work a small engine harder to make the same progress as you would in a larger-engined car.

This is most apparent when driving up a steep hill, for example.

As a result, and contrary to expectations, a small, fuel-sipping engine can actually be noisier and more vibratory than a large gas-guzzling engine.

Now that three-cylinder engines are becoming more common--a layout naturally unbalanced by the odd number of firing pulses each cycle--automakers are really having to work hard to maintain expected standards of refinement. Some are rejecting the engines altogether on refinement grounds.

Speaking to Wards Auto, Chrysler's senior NVH manager Bernie Swanson says that "fuel economy needs will drive engine noise".

That doesn't mean that all efficient vehicles will be less refined than their thirstier counterparts. But it does mean designing-in refinement, rather than addressing it with layers of sound-deadening material afterwards.

Mark Stickler, powertrain NVH manager at Ford, says the company has NVH targets at every level.

That also applies to the manufacturers whose components they use--companies making injectors or turbochargers must ensure the parts meet Ford's standards before they even go on the car.

If you cut out noise early on, then you don't need to correct it with heavy layers of soundproofing material later--weighing down the car, negating the efficiency benefits sought by smaller engines in the first place.

Active noise canceling is also useful, canceling out unpleasant noises by playing a sound with opposing wavelengths through the speakers.

Ford has previously explained its system when used on the Fusion Hybrid. The engine's firing order creates a certain resonant sound that wouldn't be pleasant for passengers--so the noise is canceled out by clever audio technology.

One thing is for sure, though: Downsizing isn't easy for automakers.

Amid concerns that smaller, turbocharged engines aren't that efficient in the real world, and others that the complex units are less reliable than more basic engines of old, customers are having to get used to very different engines than the ones they're familiar with.

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