[Alpina_B3_Lux]

I just noticed this thread and thought I could chime in with some food for thought from my own personal experience.

I've been tracking my car regularly on the Nürburgring in Germany, and am also driving quite a lot on the unlimited Autobahn. My car is a manual transmission and I have the AR design oil cooler (mounted in front of the water radiator) plus the stock oil cooler.

I've never had a limp mode while driving or tracking. However, the Nürburgring is not very hard on oil temperatures even if you do hard laps, as it is a rather fast circuit and the engine is cooled quite well through the air; much better for example than on the Hockenheimring or the smaller Grand Prix circuit at the 'Ring. When doing hard laps, the oil temps rise until about 130 degrees Celsius (266 Fahrenheit). I would describe myself an intermediate driver, so there's probably still some margin involved in this.

When flooring it on the Autobahn and driving at speeds higher than 220 km/h for a longer period of time (for example several minutes), the oil temperature goes up very quickly to almost 130 degrees Celsius. If going beyond 250 km/h, it even exceeds 130 degrees and goes until approximately 135 degrees (275 Fahrenheit). It cools down fairly quickly once I go off the throttle.

Datalogs with the BT cable confirmed this. Although this is not yet in limp-mode territory, I'm nevertheless of the opinion that the AR design oil cooler is not in an optimal location. It partially covers the water radiator, thus preventing it from being cooled by airflow, and most probably heats it up as well (although I would have to document this phenomenon further with datalogging). That is probably exacerbated with AT cars as their heatload is bigger due to the transmission being cooled as well.

I've also had the AR design aluminium radiator in my car for a few months, until it developed a leak and had to be removed again. While I had it in my car, the car heated up much more slowly (noticeable in particular in winter), but didn't seem to gain in oil temperature resistance. I can only guess as to the reasons, but I do believe that it's at least partly due to the location of the additional oil cooler.

Looking back I believe that currently the STETT oil cooler (stage 2) with the modified thermostat is probably the best solution for an oil cooler, as it replaces (if I understand it correctly) the stock cooler with a bigger core and removes (or replaces) the stock thermostat (which also helps quite a bit I think).

A garage in Germany I know quite well have now also developed a full-aluminium radiator that has the same size as the stock radiator (so no more fitting issues as I had them with the AR design radiator), but can transfer much more heat due to its design. It's costly though (around 1000 EUR), which is why I do not currently consider installing it.

Alpina_B3_Lux