Again we are talking going fast in 22 F or -5 C (below freezing temps). When I go fast at normal ambient temperatures (up to 200 mph - speedo indicated) my engine temp is normal. I am guessing that the extreme ambient cold air at super high speeds combined with the intercoolers really cools the engine down. The question really is, is it safe to maintain that speed for prolonged times at gauge indicated engine temp of 115 F? Did anyone drive in cold weather at below freezing ambient temps this fast or am I the only one?

And yes once I backed off and drove at 70 mph the gauge temp returned to normal pretty swiftly 15-20 secs.

 

Thought 22F is +5C not -5C, just googled 22F in celsius but didnt pay attention to the "-" in front... So my experience is at +5 maybe a bit lower... not -5, so just forget what I said, but I still doubt our engines will warm like 20C in 15seconds.. But did some pulls @ -5C till 170mph with my 335i, nothing wrong with those runs

 

Operating properly the thermostat will close and not allow hardly any coolant to circulate to the radiators and will instead circulate within the engine itself. You aren't going to get so much cooling from the airstream that engine temps drop like that with a properly operating thermostat IMO. Datalog your IAT, I bet it's warmer than you think. Something isn't right!

Safe? Your engine will richen the mixture thinking it's in warmup at the very least. No idea what the rest of the components might be doing but IMO it's not a great idea.

 

Well you can doubt if you like but I am simply reporting my observations. My car sits happily at 176 F / 80 C all day long at normal ambient temps. This is the first time I went 170 mph in 22 F / -5 C and my engine temps went down to 115 F. Once I backed off it climbed back to normal within 20 secs.

The question remains. Is it safe to keep on pushing with gauge indicated temp of 115 F albeit car being properly warmed up before it happens?

 

Where is the gauge reading temps from? Also I doubt my thermostat is at fault as it otherwise works without a hiccup at above freezing ambient temps. ;-).

 

http://www.renntech.org/forums/topic...ensor-install/

At 200MPH your engine should be producing plenty of heat and more than a few RPM. It's possible your pushing the thermostat open and I certainly wouldn't consider it "normal" and dismiss it. The thermostat is what regulates the engine temp and your's is falling below it's target temp.

 

I am not dismissing it. This is why am I asking if anyone else had this. But it is curious that my thermostat is operating normally in all but this "going fast in sub zero ambient temp" condition.

 

That's quite a long time to get the coolant up to operating temp. Mine gets up to temp within a few minutes with easy driving. If I had to guess, your T-stat is stuck open or partially stuck open. Should be a pretty cheap and easy repair if you DIY.

 

Reason I ask, is there's a chance the radiators had not seen any real heat yet and the cooling mass of the 'cold'/frontal cooling system brought the engine temps down quickly, not a thermostat fault per se, it is doing it job by opening from high-engine temp demands, but will not respond quickly enough to exactly regulate system temp at ~180*. 30L cooling system + accurate gauge= wild swing.
Hope that made sense.
Try the same run again but with milder acceleration and see what it does.

 

Makes sense to me.

 

Temp issues is my past (not in the porsche) was caused either by:
malfunctioning thermostat
malfunctioning waterpump
air in the system
wrong coolant type or too much water in the mix.

I don't think I read any details on your coolant type or level, check all that before looking into thermostat. How many miles on the clock?

 

UPDATE:

I observed this on the fly. I cannot talk about accuracy of the gauge. All I know is that my car runs without issues. As car was idling in the garage (warm) fans came on at the right temperature! So thermostat is working! This is an issue in below zero ambient super-fast driving condition only.

Yesterday, I went out again and did "below- zero" run again. I couldn't get to 170+ mph (traffic & not on the autobahn) but managed 150 mph. Up to 150 mph temp is rock solid at 176 F. But the needle on the gauge dips just a bit to the negative at 150 mph (I am guessing 165). So, it seems that the cold weather does something to the cooling of our cars in below-zero environment. My question still remains... is it safe to push our cars in such condition when the engine temp is reading below normal operating temperature?

 

I didn't say it took 20 min. I drove for 20 minutes before I accelerated to 170 mph. Mine gets warm in 2-3 minutes in normal conditions too. But few minutes in 22 F (-5 C) :-0 ? I don't think so mate. It takes about 10. ;-).

 

I am thinking; thermostat temporarily stuck in open position, therefore over-cooling takes place as extra-cold air is pushing in via the rads? One of those (it-works-but-it-doesn't work) issues.

Will change thermostat first. It is 10 years old.

 

been following this, and though i also dont have much experience at sustained 170 lol while watching my temp gauge but i would agree, keep it simple and swap out the t-stat. any 10+ year parts particularly "oft" replaceable ones such as a t-stat should begin there! you're right to swap it!..

and not for nothin. these cars are not at 178/182 op temp in a cpl minutes. thats for sure. try 7/10 mins! tell me if you can check your oil in a few minutes from a cold start esp in temps such as you've described. the gauge will tell that story. love that traffic limited you to only 150 though nice neighborhood! lol.