Heat induced power loss - The Unofficial BMW M5 Messageboard (m5board.com)

PhilSeastrand · 28th August 2002, 06:39

This was off the original topic so I decided to start another thread.

Quote:

Originally posted by Mpowered5
One other thing, after the mods the heat induced power loss was much worse on 90 degree plus days. It appears that the M5 reduces the timing or cuts fuel injection back as it senses an overheat situation. It appears to correlate to oil temp. Cuts back power hard as you get to 200 degrees. Looks like an oil cooler made be a required mod.

Guy

This is an interesting observation, but does not jive with my experience. During the first Sears Point day, we were getting very high engine temperatures (my water temp even got to the point the computer warned me). However, I never felt any significant power loss.

Greg, you were also seeing high temps, did you notice any power loss?

Since my car is bone stock, I wonder if its somehow related to your mods. I do notice power losses related to air-temps, but not to engine temps.

Barry · 28th August 2002, 07:27

Phil,
I've noticed that the increased ambient temperature which does at some point relate to engine temp, is more associated with power loss than engine temp. Even on our N. Cal "hot " days I notice that the engine feels sluggish even when the engine is in it's normal operating range for cool days. If it were engine temp the mods would lean more towards oil coolers, thermostats and bigger radiators and not cold air intakes (it relates to the amount of oxygen and its combustability in cool vs warm air.)
My 2 cents

stever · 28th August 2002, 07:32

as i best understand Steve Dinan's explanation, there is about a 20hp loss resulting from an "incorrect" location of the intake air sensor which heats up (and shuts down the computer) at low air flow rates

the consequence is that when driving in traffic, it heats up, you demand more power, and the computer is shut down -- when you buy the expensive intake system, Dinan re-locates the sensor --claims that it took hundreds of dyno pulls to figure this out and delayed the release of headers, etc.

on the track it's not a problem because the intake air flow is high -- in Steve's words "it's a drag race problem, not a track problem"

stever · 28th August 2002, 08:04

there is another source of heat-induced power loss in the cooling system -- the oil is cooled by the coolant system, and when the oil gets over about 250F or so it starts to overload the cooling system, the computer again richens the mixture and shuts off some power, then the over-temp light comes on -- this IS a track problem (10 laps at 80F, 8 laps at 95F in my experience) -- same problem with e46 M3's

Dinan needs customer support to develop an oil cooler which is not cheap ($3k) as they haven't sold many e36 oil coolers -- i'd go for the oil cooler, the alternative is cool-off laps in the middle of a session

any Euro sources for M5 oil cooler?