I recently purchased the Scan Gauge II to keep track of some data that the car doesn't supply by itself. It is fantastic btw, and if you don't have one you should consider getting one...Anyway, I wanted it to keep track of my boost PSI and my coolant temperature because the minis obviously don't provide that information.

After some experimentation, I found something pretty interesting.
After and only after the car is fully warmed up, I can decrease the coolant temp by around 50 degrees just by turning my air on inside the car to the highest or second highest levels. Anything less than that and the coolant temp revolves around 225. I have tried this multiple times during the day, at night, with the AC on and off and no matter what, if the coolant is at normal operating temperature of 225 and I turn the inside air on to high within 4 minutes, the coolant temp backs down to 175-185, depending on the day. Today it was around 182 and the outside air was about 95 here I Pennsylvania.

Has anyone else witnessed this? If anyone else has a Scan Gauge II can you please try this and see if you are getting the same results?
My first thought was that it was something goofy with the scan gauge, I mean, how could turning on your air dramatically decrease the temperature of your coolant? If it does work, however, that would be awesome. In theory that should be able to dramatically increase the life of the engine if its running at a cooler temp.

Another interesting observation was that in the initial warm up of the car (ie. After starting it after its been sitting for a while) the coolant temperature will not stay at 175-185 or go down to that temperature, no matter what I do with the fans until the car reaches the normal operating temp of 225. Once it hits that 225 initially and I run my air, it drops to 175-185.

 

Yup, and on 2013 models sport mode does the same thing (keeps the temps lower).. I'm ALWAYS in sport mode because of this.

The car will always hit 225 and then start cooling. I believe it does this to ensure the car is at *full* temperature before starting the cooling process.

On short trips with a hot car, I always wait for my oil and coolant temps to drop to 190/180 before turning the car off.

BTW, send the gauge back to Linear Logic if you have an N18 motor, you can get oil temp and pressure on the scan gauge as well. The shipping to them is not free, but the coding and return shipping is.

 

Yup, my 2014 justa does exactly the same thing. It's normal. As for how, remember, EVERYTHING is computer controlled. BMWs computer programmers can cool or not cool the engine any way they want. As for why, ask BMW (just don't expect an answer) !!

 

I was just going to suggest sending the unit back because they sell units specifically for your make and model car, something the standard unit doesn't share.

 

Yeah I was really hoping that I could get oil temp and pressure but it doesn't look like the scan gauge gives me that info as it exists now. I remember someone saying that sport mode keep temps cooler and when I tried it, the temperature didn't change at all. I also have a 2010 r56 with the N14 so there are clearly differences between that one and some of the newer ones.