RE: Prior Convictions: Adding lightness

RE: Prior Convictions: Adding lightness

Friday 19th January

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.

 

Author
Discussion

cybersimon

Original Poster:

186 posts

103 months

Friday 19th January
quotequote all
Porsche Cayman 981 Vs 718 ?

greenace

3 posts

149 months

Friday 19th January
quotequote all
See also 4WD v 2WD


Mark Benson

4,842 posts

203 months

Friday 19th January
quotequote all
X350 Jag XJ - I had 2003 V6 as a smoker barge for almost 2 years (I'd intended keeping it a year but it grew on me) - bought on condition so the engine was of secondary concern but I never felt short-changed at all.
Went well on the motorway, always had some poke for overtaking on B roads and was more nimble than you'd expect a drawing-room-on-wheels to be. Plus, close to 30mpg.

Lovely car and I miss it more than I thought I would.

TooMany2cvs

28,696 posts

60 months

Friday 19th January
quotequote all
cybersimon said:
Porsche Cayman 981 Vs 718 ?
"in the same car".

Moving the badge from one car to another doesn't make it the same car.

Herbs

4,269 posts

163 months

Friday 19th January
quotequote all
Agree with the sentiment but surely the V10 R8 is a better car than than the V8?

I assume you are talking about range toppers otherwise there are lots you could add. The SL range for example; SL350, SL500, SL55, SL600 SL63 etc

For the sweet spot is either the SL500 or SL55 AMG
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Krikkit

13,148 posts

115 months

Friday 19th January
quotequote all
Agree on your point Matt - taking weight out of the car is usually to the benefits of its dynamic ability.

That said, the XU5JA and XU9JA in the 205 GTI's were almost identical weight - the difference was <10kg.

TooMany2cvs

28,696 posts

60 months

Friday 19th January
quotequote all
Krikkit said:
Agree on your point Matt - taking weight out of the car is usually to the benefits of its dynamic ability.

That said, the XU5JA and XU9JA in the 205 GTI's were almost identical weight - the difference was <10kg.
Same engine, though - both XUs. The weight savings come where you've got different engine families, usually with differing numbers of cylinders.

The Douvrin-engined CXs were much nicer than the pushrod ones, f'rinstance.

bigbadbikercats

536 posts

142 months

Friday 19th January
quotequote all
Agree with the general point, disagree with some of the specifics - as far as I’m aware there wasn’t a significant difference in weight (or its distribution) between either the 1.6 and 1.9 versions of the Peugeot 205 or the Ducati 916/748.

I’m not going to comment on the Peugeot but I’ve been lucky enough to ride a number of Ducati 748/916 variants back to back on circuits over the years, and what made me consistently prefer the smaller engined variant was its smoother, revvier, more progressive power delivery. A 916 would often have me opening the throttle to exit a corner at a point in its operating range where between a steeply rising torque curve and explosive throttle response I felt (rightly or wrongly) one tiny twitch away from being high-sided to the moon on somebody else’s expensive pride and joy, the 748 in contrast would be spinning a bit faster in a much flatter part of the torque curve and I always felt I could open the throttle sooner, harder, and faster without risk of disaster.

In fairness I should point out that I never actually got bitten by a 916 (I’m probably just not fast enough for it to be a real risk), it just always felt like it might...

Benrad

381 posts

83 months

Friday 19th January
quotequote all
F-Type...

I've driven none of them but it's available with 4, 6 and 8 cylinders. Is anyone claiming the 4 cyl is the pick of the bunch?

Ditto most executive saloons

Otherwise a great point, I just enjoy the chance to fun the exceptions!

yonex

12,364 posts

102 months

Friday 19th January
quotequote all
Caterhams yes, the Rover K cars are better and the bike engined cars incredible. With motorcycles as has been said the smaller bikes have more accessible performance and are generally more agile. Litre bikes now are pushing 200HP and the roads etc are just no match for them. Anyone being honest would have more fun on a smaller bike, but huge power is addictive!

Mammasaid

938 posts

31 months

Friday 19th January
quotequote all
Benrad said:
F-Type...

I've driven none of them but it's available with 4, 6 and 8 cylinders. Is anyone claiming the 4 cyl is the pick of the bunch?

Ditto most executive saloons

Otherwise a great point, I just enjoy the chance to fun the exceptions!
Yes,

Top Gear

Top Gear said:
Objectively this is a better F-Type.
Car Magazine

Car Magazine said:
It’s very good, if not flawless..

tjw110

488 posts

156 months

Friday 19th January
quotequote all
Would you take a New F type 2.0 over a v6 or v8?

Mammasaid

938 posts

31 months

Friday 19th January
quotequote all
tjw110 said:
Would you take a New F type 2.0 over a v6 or v8?
Unfortunately, I'm not in a position take any of them frown

ACW

50 posts

161 months

Friday 19th January
quotequote all
Good points but what was missed was the downshifting (in a manual at least) that can ruin a light car's driveability. Anything lightweight doesn't work great with a big displacement engine because the weight of the rotating mass will often lock up rear tyres, and make it 'chug' at low rpm in around-town driving.

skylarking808

173 posts

20 months

Friday 19th January
quotequote all
My experience with BMW E30's echos this.

The E30 1.8l sport was a better handling/steer than the 2.5l sport. Better balanced so the rear was not as light, and improved direction changes etc.I think this was the reason the original M3 had a four pot?

V8 FOU

2,566 posts

81 months

Friday 19th January
quotequote all
Alfa 147 etc 2.0Ts vs V6.
Difficult call as the V6 is soooo sweet. But it is a whole heap heavier than the 2.0 TS - therefore the TS car handles a lot better.

Ved

3,808 posts

109 months

Friday 19th January
quotequote all
I agree with some of the article but a smaller, typically 4 cylinder engine, will never be as desirable or sound as good as a 6 or 8 and cars a lot of people still buy with the heart, or at least their ears. All three of my cars have 6 cylinder engines and have more capable handling models with smaller engines further down the range:

R32 to GTI
3.0 Outback to 2.0 Outback (both wallowy barges, mind)
3.0 GTV to 2.0 GTV

Noise plays a big part in a car for me and I'll take a drop in finesse to get it.

PHMatt

566 posts

82 months

Friday 19th January
quotequote all
skylarking808 said:
My experience with BMW E30's echos this.

The E30 1.8l sport was a better handling/steer than the 2.5l sport. Better balanced so the rear was not as light, and improved direction changes etc.I think this was the reason the original M3 had a four pot?
Beat me to it.
This likely had something to do with the 6 pots of the time having iron blocks that weighed a st ton though.

Although.... the S54 in the E46 M3 had an iron block whereas the regular M54 6 pots had aluminum and were much lighter,

Strange eh!

PHMatt

566 posts

82 months

Friday 19th January
quotequote all
skylarking808 said:
My experience with BMW E30's echos this.

The E30 1.8l sport was a better handling/steer than the 2.5l sport. Better balanced so the rear was not as light, and improved direction changes etc.I think this was the reason the original M3 had a four pot?
Beat me to it.
This likely had something to do with the 6 pots of the time having iron blocks that weighed a st ton though.

Although.... the S54 in the E46 M3 had an iron block whereas the regular M54 6 pots had aluminum and were much lighter,

Strange eh!

Mound Dawg

1,830 posts

108 months

Friday 19th January
quotequote all
Alfa 75s are the same, yeah the V6 makes a great noise but the extra weight and overlong gearing mean that point to point the four pot Twinspark is a faster car.