Drop in temp has to be map tstat related. I think it just caught you by surprise. The relatively cool ambient combined with the computer deciding to cool off.

It's very dramatic on the n55 motor. When tstat opens it also kicks the coolant pump 67% faster and ECT temp drops from 109 to 95 in well under a minute maybe half.

This will happen any time you hit a hill and engine develops load. If it's a small hill, temp might only drop to 100 or high 90s but even just a bit of throttle to overtake and temps will drop 5-8c.

On n62 with standard coolant pump the change might not be as fast, but with big ass radiator just need water flow and it'll cool shit down right quick.

I'm sure you always have ac on but if it cycled on right at the same time, I'm sure the parameters are set to keep things cooler when AC running.

Interesting about no aux fan.

My car only has aux fan.


–awr–

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)