Reduced power due to winter blend?

[Daxos]

This is only based on my butt dyno, but I feel like my car hasn't been pulling as strong ever since I filled up with winter blend. I'm still using 93 octane and there's not a massive difference, but it does feel like it is not pulling as strong.

Now I was always under the impression cars would make more HP or make higher HP more consistently during winter due to colder temperatures, but in my case the opposite seems to be the case.

Is it possible this is due to the winter blend?

[CanAutM3]

Modern FI engines are able to compensate for atmospheric conditions. So it is quite possible your S55 is simply holding back on boost to not exceed the rated power.

[aerostar]

Originally Posted by Daxos

This is only based on my butt dyno, but I feel like my car hasn't been pulling as strong ever since I filled up with winter blend. I'm still using 93 octane and there's not a massive difference, but it does feel like it is not pulling as strong.

Now I was always under the impression cars would make more HP or make higher HP more consistently during winter due to colder temperatures, but in my case the opposite seems to be the case.

Is it possible this is due to the winter blend?

Usually turbo motors will feel much faster in the cold, yes.

Do you have winter tires on?

[Daxos]

No winter tires. 265/295 MPSS. To clarify, my car is modded as well. VF Stage 2 ECU tune, TCU tune, Akrapovic downpipes, midpipe and rear exhaust, VRSF Chargepipes, Dinan Heat Exchanger, AFE filter and charcoal filters have been removed.

Maybe I'm just imaging it since I don't have any dyno numbers to back it up but it could swear it felt slower the last time I drove it.

[madpacket]

Here is a gadget that will precisely measure your car's performance. It has nice iPhone app if that's your platform. Otherwise a removable memory card for reporting.

http://www.racelogic.co.uk/usastore/...uct=VBOX-Sport

[MonacoMurphy]

Most probably a traction, or lack thereof, issue.

You always drive with TC off? Then you're spinning but maybe not so much you can feel it, but just enough. Or you have TC on and its just kicking in all the time.

[psedog]

I agree with Murphy. The roads are colder so your rubber isn't going to be as stick as it would in the summer time.

[BhamDavid]

Winter blend gasoline has more lightweight volatiles which vaporize at a lower temperature to aid starting. As a result, a gallon of winter gasoline will weigh slightly less than summer gasoline. Less mass equals less BTU content therefore less power output.

But this should be more than offset by the increased mass of cooler air since the ratio of air to gas is just under 15 to 1.

I'd agree with those that think decreased traction is the issue here.

[Daxos]

Thanks for the feedback everyone. I don't think this was a traction issue as I went WOT in fourth on the highway. I was in MDM mode but didn't feel any slippage and the traction light didn't come on, either.

It was the first time I actually took the car out in cold weather (sub 40 degrees F) and had my TCU/ECU reset just a few weeks prior because of what appeared to be a slipping clutch. Is it possible the ECU was learning cold weather driving habits?

[CanAutM3]

Originally Posted by BhamDavid

Winter blend gasoline has more lightweight volatiles which vaporize at a lower temperature to aid starting. As a result, a gallon of winter gasoline will weigh slightly less than summer gasoline. Less mass equals less BTU content therefore less power output.

But this should be more than offset by the increased mass of cooler air since the ratio of air to gas is just under 15 to 1.

I'd agree with those that think decreased traction is the issue here.

How much a gallon weighs is irrelevant here since the engines are not tuned to run on volume. The "15:1" (sic) ratio you mention is a mass ratio. It's about the calorific value of the fuel (how much heat energy is released per unit weight of fuel).

[BhamDavid]

Originally Posted by CanAutM3

How much a gallon weighs is irrelevant here since the engines are not tuned to run on volume. The "15:1" (sic) ratio you mention is a mass ratio. It's about the calorific value of the fuel (how much heat energy is released per unit weight of fuel).

So your saying that the engine KNOWS the weight of the fuel? Not buying it. The injection is timed. It runs on volume.

[E90Fleet]

Originally Posted by BhamDavid

So your saying that the engine KNOWS the weight of the fuel? Not buying it. The injection is timed. It runs on volume.

Simply,

The fuel and air burns per weight, not volume. (chemistry)
The weight of the air is determined by the DME using the intake hot film air mass meters.

The fuel is injected using time.
If the fuel weight changes the resulting exhaust gas will change
The before catalyst oxygen sensors will pick up the change and the DME will alter the injection time to correct.

The S55 like all modern BMW direct Injection gasoline engines can adjust each injector individually.
The engine DME runs periodic tests per cylinder to determine the exact flow rate for each injector and adjusts each to get each cylinder running the same ( Hence why adaptions have to be cleared when injectors are replaced)


So it does not know the mass of the fuel before it enters the cylinder, but it determines if the correct mass was injected after it was burnt. If the ratio is incorrect, it very quickly changes the injection time to correct.

[Lups]

Originally Posted by Daxos

Thanks for the feedback everyone. I don't think this was a traction issue as I went WOT in fourth on the highway. I was in MDM mode but didn't feel any slippage and the traction light didn't come on, either.

It was the first time I actually took the car out in cold weather (sub 40 degrees F) and had my TCU/ECU reset just a few weeks prior because of what appeared to be a slipping clutch. Is it possible the ECU was learning cold weather driving habits?

Mdm mode, issue solved.

The tc in the USA is not only harmful, it is insane. Get euro coding but be very aware if you're in a dct.

According to my observations us drivers are very much having a winter nap when we get even close to 32f.

I went to as far as to 27f with mine and losing power was never an issue. (traction was issue after hitting 40f)

I did 30 something k with my F82, but I've also driven one in - 32c (around -20, a bit more) temperatures in Finland. I for the few k's I did not see a drop in power. I did look like a pussy a lot though

[Lups]

Originally Posted by BhamDavid

So your saying that the engine KNOWS the weight of the fuel? Not buying it. The injection is timed. It runs on volume.

So cold weather= more fuel since it (come on Americans and Canadians, help me out with the word!) goes smaller? That means engines run better in cool air which is basically what everyone has ever written.

They intake the amount they are restricted to intake, how much energy the amount taken has in it or how well it can be used can be measured.

(I don't write engineer in English)

[psedog]

Originally Posted by Lups

So cold weather= more fuel since it (come on Americans and Canadians, help me out with the word!) goes smaller? That means engines run better in cool air which is basically what everyone has ever written.

They intake the amount they are restricted to intake, how much energy the amount taken has in it or how well it can be used can be measured.

(I don't write engineer in English)

The word you're looking for is concentrated.

[CanAutM3]

Originally Posted by BhamDavid

So your saying that the engine KNOWS the weight of the fuel? Not buying it. The injection is timed. It runs on volume.

E90Fleet beat me to it.

Further, the density of the fuel also changes with temperature. The colder it gets, the more mass of fuel you're getting for a given volume. The DME also needs to correct for that.

Also consider that when you buy gas at the pump, they are really selling it to you by mass and not volume, even if the pump says gallons or liters. Notice the small print that says volume corrected to X temperature (15degC in Canada). That's because they are selling you an energy content and energy content is proportional to mass, not volume.

[Lups]

Originally Posted by psedog

The word you're looking for is concentrated.

Yeah, it was. Thanks man!

I still think those evil little shits (engineers) come up with words like that just to mess with the normal people.

[Alpine300zhp]

Originally Posted by Daxos

This is only based on my butt dyno, but I feel like my car hasn't been pulling as strong ever since I filled up with winter blend. I'm still using 93 octane and there's not a massive difference, but it does feel like it is not pulling as strong.

Now I was always under the impression cars would make more HP or make higher HP more consistently during winter due to colder temperatures, but in my case the opposite seems to be the case.

Is it possible this is due to the winter blend?

I cannot speak to winter blend, but I do notice a difference if I do not use Shell 93 octane. My car pulls harder and gets better fuel economy on Shell versus other gasoline brands. The next closest in performance is Chevron. I am not making this up, I have done it enough times that I know it is true.