Let's compare 4.0T heat exchanges...

[Vol 4.0T]

s6

[markreed]

I would be curious to see what the addition of a larger heat exchanger alone would do...more surface area and a high fluid capacity.

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[LW3]

What year/model do you have?

[markreed]

Same...

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[MadAboutCars]

My MY16 has the same smaller looking unit, but today after driving over 100km, parking for 1/2 and hour, and then driving for another 10 minutes the temperature of that unit on the front outside, using a laser temperature gauge, was only 35C. The thin black radiator above it was 61C. The smaller unit at the bottom is quite thick compared to the other units shown above in this thread. I don't know what the black radiator is, but the main silver radiator seems to be behind it.

[jfeger]

I'm probably totally wrong here...but here goes anyway....

I took a look at the hose and connection diagram for the cooling system. The interesting thing is, the charged air cooling path appears to tie into the transmission cooling path. Additionally, I can't make sense of the hose connections from the charged air heat exchanger into the turbos. They appear to get mixed in with the engine cooling path at some point. I'm sure I'm reading it wrong, but it certainly appears to share the coolant fluid throughout all the same systems. I counted an ATF cooler, oil cooler, charged air cooler, engine cooler/radiator, all with hoses seemingly connected.

The manual provided a key that identified "green" as charged air cooling system, "orange" as the ATF cooling system, and a few others. In the end, they all joined at some point, and more interesting, the turbos were only connected with "orange", which was ATF according to the key.


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[jfeger]

My MY16 has the same smaller looking unit, but today after driving over 100km, parking for 1/2 and hour, and then driving for another 10 minutes the temperature of that unit on the front outside, using a laser temperature gauge, was only 35C. The thin black radiator above it was 61C. The smaller unit at the bottom is quite thick compared to the other units shown above in this thread. I don't know what the black radiator is, but the main silver radiator seems to be behind it.

You should have an engine cooler/radiator, the charged air cooler, and the HVAC system up there.