I've read that they don't want to beset by drivers who worry over the course of a day that their car is running too hot. Easier to dumb the thing down than educate the owners. You know that isn't true, right?

 

This is quite common practice in automobiles for at least the last ten years or more. The temp gauge is buffered so that it reads a specific temp (175 in the case of Potsche) and doesn't read higher until some higher threshold is met. They don't want owners stressing over the fact there temp gauge reads 175 on day and 185 the next. The average motorist isn't smart enough the realize that once the thermostat opens, the engine will run at variable temperatures above that depending upon load and ambient temperature.

 

You are absolutely right about the water temp guage. I have a OBDII bluetooth adapter I use with a Driod app called Torque. It monitors realtime values for most of the car performance sensors and can read and reset fault codes.

The coolant temps on my car run higher than the dash gauge indicated 175. I can't remember exact temps right now. Water temps also fluctuate where as the dash guage never moves. The oil temp guage seems to more represent real oil temp. I just recently got the OBDII adapter and have not had a chance to see what is going on with water temps on the track. I wish I new now what was going on on the track with water temps so I would know if the third radiator is necessary. $189 is a good deal.

Another cool sensor I have monitored, is the intake temp in realtime. When I'm sitting still idoling, intake temps rise alot and fast. It's unbelievable when you start moving how fast and how much intake air temps drop. IMHO the stock intake is truly a cold air intake induction system. I can't imagine how the two most popular aftermark systems being sold could possibly do as good or better. No wonder race teams use the stock system wrapped in insulation.

 

Great stuff! When you do get a chance to get real water temp readings on the track please post your findings. Before and after radiator results could earn you a place in 6SPD history

 

I believe the important thing here is the oil temperature. I saw 25-30F drop in oil temperature with the 3rd radiator in my 09 C2S 6 speed. A friend with an identical car except PDK saw a 35F drop in oil temperature. He went from a 270F to a 235F oil temp on track. That is worthwhile.

 

Since PDK cars come with third radiator. Does that radiator cool engine water or transmission oil?

 

Not all PDK cars came with the third radiator. I can't remember when they were added. My '11' GTS PDK came standard the third radiator.

On both the 6 speed and PDK the extra cooling capacity is directed at the water. Since the oil cooler is oil to water you get added benefit reduce oil temps.

 

early '09 PDK cars came without 3rd radiator then after some time factory started putting them on every PDK car to fight overheat. it seems to me a proper solution would be to add tranny oil radiator instead.

 

Adding a larger transmission oil cooler would most likely be more difficult due to packaging than adding the third radiator in front. However, it would most likely be an easier item to optimize for heat transfer.

The extra front mount radiator will still reduce the heat load on the trans and engine.