Prior Convictions: Adding lightness

Matt ponders why a smaller engine often makes for a better car...

Aha, a small engine is coming to the Bentley Bentayga SUV. Well, a smaller engine, these things being relative, after all. The Bentayga, which has until now been offered with a 6.0-litre W12 will shortly arrive with a 4.0-litre, twin turbocharged V8 motor beneath a bonnet that remains of considerable girth.

Considerable enough girth that the Bentayga's quoted kerb weight will go from 2,440kg for the W12, to 2,395kg for the V8, which doesn't sound like much of a loss in the scheme of things, because it isn't. Those 45kg only represent a 1.8 per cent reduction in weight over the W12.

But there are two things of note: one, all of that weight is over the nose and, two, has there ever been a case where a lighter engine has not made for a better car?

I don't think there has. And the reasons it should do are obvious enough. Fit a lighter component and it takes less effort to turn it and less effort to control the its movement over bumps, it takes less effort to stop and less effort to steer. So, all else being equal, you improve a car's ride, handling, braking and steering; although probably not acceleration because, y'know, bigger engine, more power.

But sod the power for a minute. There's only so much pleasure you can get from acceleration, and it doesn't last very long. Yet improved ride, handling and steering give you benefits all of the time.

Cases in point, then? The Peugeot 205 GTi 1.6 was, purists said, sweeter than the 1.9; the Audi R8 with a V8 was more agile than the V10 that joined it later; the Jaguar XK with a naturally-aspirated V8 was more pleasing, even senior ride and handling engineers would admit, than the supercharged XKR. No ordinary, cooking model of a daily hatchback is better to drive with a diesel engine. Caterham 7s were - are - at their best with lighter motors; I had an HPC with a Vauxhall engine and despite other accepted dynamic items of choice - no interior, 13-inch wheels, and so on, the steering was heavy and a contemporary Rover K-series car was nicer. This stuff extends beyond cars, too: Ducati's 748 was said to handle better than the 916, and the whole 600cc sports bike class has a reputation for being more agile than 1.0-litre machines.

And of course there are the Bentley examples. Never, since Bentley first put a V8 and a W12 engine in the same car at the same time, has the bigger motor been a better car, usually to Bentley's slight resignation.

This time it's meant to be different. The W12 has always been a very short motor but in its latest redesign it's lighter, too, and is meant to sound better. But physics matters. I know 45kg doesn't sound like a lot but it'll make a difference. Just how much, we'll find out soon enough. And although I won't pre-judge any new car, if it isn't a nicer car to drive than the W12, I think that would put it in a class of one.

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cybersimon

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