M settings and resulting fuel economy

[steakandchips]

Hi,

Does anyone think that the more sporty settings on modern M cars are actually less economical on a long motorway journey? Common sense would tell me that cruising at a steady 80mph in seventh gear will require exactly the same amount of fuel no matter which mappings the throttle, suspension and gearbox are set to. I imagine city driving would probably be less economical in M1 and M2 but I wonder how much difference setting your car to Sport rather then Efficient really makes. Anybody found any great difference in the real world?

S&C

[RichardM5]

In my M6, selecting the Sport+ throttle setting causes the engine temperature to drop by about 20 degrees, 102/3 -> 83/4. Running cooler will decrease efficiency. If you use D with Sport or Sport+ settings it will hold a lower gear longer which will decrease efficiency.

[theboss]

I read about this the other day...

http://f10.m5post.com/forums/showthread.php?t=5888...

BMW M Head of Engine Development said:

By selecting the Sport or Sport plus accelerator mode, we can really feel the additional boost to the response. How does that work?

In Sport or Sport plus mode, a suitable VALVETRONIC controller and the waste gates keep the turbocharger in the higher speed range. Normally, the waste gate used to regulate the charging pressure opens so that the exhaust gas flows out with the minimum possible loss. Pressure is built up again only when I hit the accelerator. For an improved response, I leave the waste gate closed until I need it for regulating. The exhaust gas then always passes over the turbine, which then runs at a considerably higher speed. When even more power is demanded, it is immediately available. However, I have a gradually rising counterpressure that causes a slight rise in consumption.

[Wills2]

Interesting, so sport/+ modes spin up the turbos to give a more instant response I like that!

How does that correlate to the engine running cooler?

[steakandchips]

I wonder if any of this talk about turbos spooling is related to an issue I've been having recently. When I'm moving at relatively low speeds, say between 20mph and 50mph, if I press the throttle I occasionally seem to get a momentary loss of power, with an almost imperceptible lurch as the car loses momentum, before everything pulls itself together and I start to accelerate again. It doesn't last for more than a second or two but it's a definite loss of power.

It's not at all like the usual turbo lag that I've noticed since I've had the car (2013 F10 M5) which has always been consistent and isn't too noticeable. This is something inconsistent and certainly noticeable. Perhaps some gremlin in the engine management? It's not been bad enough or happening often enough to take to the dealer but I'll mention it when the car goes in for an oil service in July (incidentally, the car still hasn't asked for a single drop of oil in almost 15,000 miles).

Does this sound familiar to anyone?

S&C

[Wills2]

I've not noticed that exactly but the car does vary in its response from time to time.

One thing I have noticed is that when in D1 it some times will stay in 2nd when I come to a stop and some times drop to 1st. It seems to be random but it can cause issues as 1st gear needs very little throttle to get moving 2nd needs more so when pulling out into traffic it's slightly disconcerting when it decides on 2nd gear but you haven't noticed.

Edited by Wills2 on Tuesday 28th April 17:14

[theboss]

Wills2 said:

I've noticed that exactly but the car does vary in its response from time to time.

One thing I have noticed is that when in D1 it some times will stay in 2nd when I come to a stop and some times drop to 1st. It seems to be random but it can cause issues as 1st gear needs very little throttle to get moving 2nd needs more so when pulling out into traffic it's slightly disconcerting when it decides on 2nd gear but you haven't noticed.

Can't shed any light on the responsiveness issue, but I've had exactly the same with 1st/2nd when coming to a halt in D1. I wouldn't mind if it were entirely consistent either way, but given that throttle input required for the take-up varies enormously between the two, its slightly disconcerting that it varies randomly.

[Wills2]

In traffic and urban driving I'd prefer that it starts in 2nd all the time as the longer gear means smoother progress and I like the pick up and allows more throttle input and you can be more positive and lean on the torque.

But it does require a lot more input as you say.

[davewhitt]

i read somewhere that in d1 when the car has warmed up it should always start in 2nd gear. there is a default setting that stops this if you have a worn clutch, or other clutch related faults

[joscal]

Wills2 said:

I've not noticed that exactly but the car does vary in its response from time to time.

One thing I have noticed is that when in D1 it some times will stay in 2nd when I come to a stop and some times drop to 1st. It seems to be random but it can cause issues as 1st gear needs very little throttle to get moving 2nd needs more so when pulling out into traffic it's slightly disconcerting when it decides on 2nd gear but you haven't noticed.

Edited by Wills2 on Tuesday 28th April 17:14

Mine does this too, can't figure out the parameters but definitely irritating until you notice.