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      07-25-2011, 07:20 AM   #589
vasillalov
Mad Linux Guru On The Loose
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Drives: 2008 335i Sedan
Join Date: Aug 2009
Location: Chicago, IL

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2008 335i E90  [4.00]
Alright folks,

I've been following this thread for a while now gathering information and learning about the overheating/limp mode issues of our engines on the track. While I have not ever taken my car to a real track yet, I do believe that I have some interesting information to contribute:

Last week Chicago (and other part of the country) was hit by a serious heat wave. On couple of days I've seen 100+F daytime temperatures which for Chicago is quite hot. Pair that with 70+% humidity and you have some really nasty weather when it comes to cars.

When I am stuck in traffic in Chicago in such weather conditions, my oil temps will hover at the 240-250F mark, but never exceed that. I have the stock oil cooler and 6MT. I don't have any additional cooling modifications whatsoever. I do also have the Rixter P3 boost gauge which allows me to monitor all kinds of CAN bus data including engine coolant temperature. On a hot day, in traffic, the coolant temperature will go as high as 230-240F.

Last week, it got so hot, that I had to turn on the AC. And to my surprise, the AC dropped BOTH the coolant temperature AND the oil temperature to 180-190F. I was surprised! Not only that this works in traffic, but it also works while romping on the gas pedal on the highway! I did series of WOT pulls from 20mph up to 90 mph and not once did the coolant and oil temps went above 190F. Again, I had the AC on the whole time and the fan was on the 4th speed.

What I think is worth noting here is this:

* The oil temperatures will follow closely the coolant temperatures. That Stett Oil cooler with the 180F thermostat is just a temporary patch. Once the coolant temps get up to 240, there is no way to keep the oil temps at 180F.

* It will be extremely beneficial for track people to cool off their engines by running their cars with AC on. Not only this will circulate the oil through the oil cooler, thus cooling it, but it will drop BOTH the coolant and oil temps to 180-190F.

* If we want to improve our cars to last longer in the track, we should be concentrating on better radiators, cooling fans and airflow to the radiators. I think that going down the path of improving oil cooling is not beneficial unless your car did not come with stock oil cooler.


If someone is willing to test my theory, that would be awesome. Do a track day with your AC on, windows closed and blower fan on speed 4 or higher. You will be amazed.
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Last edited by vasillalov; 07-25-2011 at 07:26 AM.