BMW and M Power Owners

Are other points not being ignored However? Cars have a greater number of systems to power compared to 10 or 15 years ago, all of which use additional fuel. Stopping distances are shorter thanks to better grip, which uses more fuel.
They're generally bigger which means greater air resistance and thus more fuel. I think they've done rather well to maintain or even improve efficiency like they have.
 
Turbos do increase efficiency. They reduce pumping losses and are ideal for cruising on motorway.

Can't fault the 3.0 turbo engines for their ability to do everything. The V8 is horrendous on fuel even on motorways
 
[TW]Fox said:
What?

Tyre rolling resistance is at an all-time low..
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You can't have low rolling resistance without decreasing braking performance. Therefore to increase stopping power you have to compromise on efficiency. Yes the balance is better than it's ever been but if you want performance tyres you have to put up with increased fuel usage.
 
Dis86 said:
You can't have low rolling resistance without decreasing braking performance. Therefore to increase stopping power you have to compromise on efficiency. Yes the balance is better than it's ever been but if you want performance tyres you have to put up with increased fuel usage.
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Fuel usage with performance tyres has been improving continually for years and years.

I remember the dramatic effect fitting a set of Eagle F1 GSD3 used to have!
 
Modern tyres have got wider which will always be a big factor rather than just looking at rolling resistance performance evolution.

10 yrs ago there wasn't the focus on weight as we see now. Aerodynamic I've generally got better but the frontal areas of cars now are massive due to pedestrian safety.

It's things like turbos, downsizing (to keep the performance )and direct injection that have really moved petrol efficiency on
 
Simon said:
Modern tyres have got wider which will always be a big factor rather than just looking at rolling resistance performance evolution.
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The tyre width changes were a long time ago though - a 1990 5 530i had 205 width tyres, my 2001 530i has 265 width tyres and my 2015 530 has tyres just 10mm wider.

On the 3 Series the 19 inch tyre width hasn't changed in a decade...
 
Dis86 said:
You can't have low rolling resistance without decreasing braking performance. Therefore to increase stopping power you have to compromise on efficiency. Yes the balance is better than it's ever been but if you want performance tyres you have to put up with increased fuel usage.
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Yes you can, you just tune the belt reinforcement and select different compounds.
 
Jonnycoupe said:
Yes you can, you just tune the belt reinforcement and select different compounds.
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No. You're still striking a balance between the two there. Yes a tyre of a different compound may be better than a tyre of another but you're then paying more for the compound. Within the same compound you can push towards braking efficiency or rolling resistance reduction.
Not both.
The two forces oppose one another. You cannot change physics.
 
[TW]Fox said:
So you're saying that that if you had two identical engines but one had a turbo, it would be more fuel efficient by a material margin?
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I would expect they are more fuel efficient with a turbo when cruising mainly down to the low down torque they provide allowing a tall 8th gear. I can't remember the exact revs but generally in top gear the turbo engines are at least 1000revs lower over the NA engines.

I assume the main reason holding back fuel efficiency is the strict emission rules.
 
Dis86 said:
No. You're still striking a balance between the two there. Yes a tyre of a different compound may be better than a tyre of another but you're then paying more for the compound. Within the same compound you can push towards braking efficiency or rolling resistance reduction.
Not both.
The two forces oppose one another. You cannot change physics.
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No one would 'lock' a compound like you suggest. You are confusing tyre mu with tyre RRc (rolling resistance coefficient). Pirrelli give a clue with their Cinturato range.

You can not change cliche comments... only challenge them.
 
[TW]Fox said:
We are specifically discussing 3 litre BMWs though so why do that?



So you're saying that that if you had two identical engines but one had a turbo, it would be more fuel efficient by a material margin?
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Yes and far more material of a difference than tyres !

Changing tyres is relatively cheap for OEMs, certainly incrementally.

Turbos are not. If tyres were the solution for the CO2 challenges of the OEM we would see a lot more super efficient tyres (and probably thinner with more aerodynamic wheels). However sticking a turbo on gives such an big improvement that it is worth the cost and performance driven tyres.

PV diagrams and the reduction in pumping losses make the benefit of a turbo very clear. You are using waste energy to do something.

What sort of increase did you see on tyres ? I recall you jumping on people who made 2-3mpg claims due to 98Ron fuel.

[TW]Fox said:
We are specifically discussing 3 litre BMWs though so why do that?
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So why was a 3 series your example?

What about 1 series tyre sizes ?
 
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Simon said:
What sort of increase did you see on tyres ? I recall you jumping on people who made 2-3mpg claims due to 98Ron fuel.
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You recall badly then as I've never jumped on people for suggesting a car designed for 98 Ron fuel would be less efficient when run on 95 ron. It even specifically stated that in my cars handbook and I've quoted from it on here in the past.

Tyre wise I increased consumption almost 10% moving to the GS D3 and gradually got it back with subsequent iterations of the Assymetric. The GSD3 was notorious for high rolling resistance.
 
Jonnycoupe said:
No one would 'lock' a compound like you suggest. You are confusing tyre mu with tyre RRc (rolling resistance coefficient). Pirrelli give a clue with their Cinturato range.

You can not change cliche comments... only challenge them.
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But we're not talking about a fundamental change to tyre design that occurred 50 years ago. We're not talking about race or track tyres. We're talking about standard road tyres which at the budget end of the market will probably have had the same compound for the last 20 years and all that will change is the surface patterns. At the premium end then Yes, the compound will change but the design of a tyre will still favour efficiency or performance. Otherwise why do we have the same companies producing multiple tyres at the same or similar price ranges with a focus on one or the other?
 
Simon said:
So why was a 3 series your example?
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People are discussing consumption on the 1 series, 3 series and 5 series.

What about 1 series tyre sizes ?
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There has been no change in tyre size on the 135 since the original 1 Series, though there is now an optional 19 inch wheel which is 10mm wider tyre wise. But the 18 inch option remains the same.

There was a big jump in tyre sizes some years ago but it's very much calmed down now, I guess we reached the point of diminishing returns.
 
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