Those who run their A4 C5 on road course tracks may find this helpful.

I began running my A4 on track in early 2011, Saturday was Track Day 26.

It became clear early on that keeping the drive train cool would require some modifications. By December 2014 I had already installed a DeWitts radiator with transmission cooler and engine oil cooler along with a B&M finned aluminum Transmission pan (two extra quarts). The transmission had been routinely going over 250 degrees on track so I installed the following auxiliary cooler, December 2014.


2014 tube and fin cooler before center air dam re installed.

This cooler helped for another seven years and seemed fine at Laguna Seca. But I got faster -- incrementally the transmission temperatures crept up -- especially after several sessions on track. Then I moved to Arizona and began driving at Arizona Motorsports Park, just West of the greater Phoenix area. For the last two years at AMP in April and May, transmission temperatures began hitting 250 at about lap 9, I was coming off track a lap early.

Two weeks ago I installed an LDP 47391 low pressure drop parallel flow auxiliary cooler, rated for a 40,000 pounds gross weight vehicle:





47391 installed, center air dam reinstalled.


The new 40,000 pound gross vehicle weight auxiliary transmission cooler absolutely works. Saturday April 15th at the end of the 3rd session with outside air climbing through 80, the transmission temperature never passed 205 F. In February, same track, OLD COOLER on a cooler day, after the 3rd session I came off track one lap early with the transmission temperature going through 250 F.

Downside is that the engine coolant temperature on 3rd session peaked at 230 F, 10 degrees higher than before. My competing theories are that --the new auxiliary cooler is slowing air flow through the radiator--or that the heat rejection of the new cooler is challenging the radiator capacity. (??) The radiator is a high capacity aluminum one made by DeWitts that I put in in September of 2013.

The good news is that both coolant and transmission temperatures dropped rapidly during cool down lap.

The new cooler is mounted similar to the old but with new brackets and is about 3/4 inch clear of the condenser, just like the condenser is about 3/4 inch clear of the radiator. Flow is hot from trans to radiator cooler, to auxiliary cooler, back to trans. I used 3/8" hoses and managed a shorter hose route by routing the hoses from the top of the cooler to avoid an air block, through the passenger side of the radiator shroud directly to upper radiator trans connection and return to trans.

I am not going to complain. On the other hand I may adjust the coolant antifreeze ratio to 25% instead of 50% and add water wetter. The coolant is due for a change anyway.

 

This is why, on my Camaro, I installed an engine oil cooler behind the radiator. My priority is to manage water temps.



On my Z06, I installed an oil cooler behind the license plate and ducted it. Again, I did not want to add heat to the water from the oil. Were I in your shoes, I'd have added a ducted cooler fed by the front bumper hole that's screened on a Z06 and where the fog lights go on a coupe.
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Great info. Thanks.
I wonder if it might run cooler yet if you were to bypass the radiator cooler?
If you think about it, the coolest the radiator portion can cool the fluid would be the temp of the coolant.
Sure wood be an interesting experiment.

205 is no issue at all.