High temps affecting performance ?

[Timberwolf]

I have to say despite the obvious lack of sharpness the car has due to extreme 90+ degree temps, it still pulls very hard. The water to air intercoolers seem to do their job with a few highway pulls. I don't know about track duty, but for street, I'm impressed.

[M54ccibo]

IMHO I take dyno results with a grain of salt. If there is not adequate airflow over the intercooler radiators I assume that the ECU is going to back off boost to prevent overheating, thus, a large shift in WHP. In real-world driving if there is a power loss it I'd guess it isn't close to 50 WHP. A number of us here in SoCal have made multiple WOT runs in the heat and this is not a major issue. Sitting in traffic, then running WOT for 3/4 mile will be, just as forcing heat soak will cause the dyno results shown.

Like I stated above, when the airflow is disrupted to the radiators - as was the case at COTA under lead-follow as we hit 145-150MPH before hard braking - the car would go into "reduce temp mode" for 30 sec. That is after WOT for 3/4 of a mile, ambient temp over 90, track temp even higher. Keep in mind this this did not happen to the lead car. Also asked the instructors if they experienced this and they said no. Oh, and if you kept the speed under 130MPH - no issues.

I'd argue that the empirical data shows disturbing the airflow to the intercooler radiators causes issues. Not saying there isn't a potential heat soak problem, rather, that is only the case if airflow is compromised, and this issue's magnitude is proportional to compromised cooling.

Not to mention the fact that no matter the number of fans you put in front of the car on the dyno the fluid dynamics at play are not even close to what the car encounters while moving forward. You just cannot replicate the areas of high and low pressure and the movement of air while still. Had a long discussion with Dr. Biermann about this, specifically on the oil cooler and the effect of Bernoulli's principle.

[noushy]

Wow thanks for the info. Absolutely my M6 loses power over 90 degrees ambient temp when the humidity is high. I had pulled into my dealership to talk to the parts manager, car cooled off in the service bay (temp read 80). When I left about 30 mins later the car was breaking loose in second gear. About 15 mins later the temp read 96 and the car was significantly slower almost sluggish like turbo lag. Not sure how to quantify the loss but it is noticeable. I think humidity plays just as big a role as temp.

Noushy

[mstmng]

Originally Posted by Simon H

Just felt like, the car didnt have its usual surge of torque, going up through the rev range. I know one of the tuners, early on in the cars release, said that the M5 suffers with heat soak, and i think i felt it a little today.

felt the difference as well, was pushing car hard the other night and next day car felt "exhausted" after night during 30* day

[04S]

I have pushed the car in 90+ degrees here and never had an issue. I have also tracked the car pretty hard on an 85 degree day with no issue.

Per M54ccibo's comments though, I was not in either case following another car but was out in the open with clean airflow over the car.

I have experienced the car go into limp mode on hotlaps of the old Philip Island grand prix circuit in Victoria with the BMW driving instructors, twice, on 80+ degree days, but in each case the car had less than 5km of fuel range left which I think explains the limp mode.