Auxiliary Radiator Delete

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Worth pointing out that the aux radiators are not actuive all the time but thermostat controlled.

I think what Dave was meaning that of course surface area is everything with radiators however one extra aux rad (which lets be honest, isn't that big or efficient and a good 1/3 of it is covered by the bumper vent anyway) isn't going to add sufficient surface area such that when the car isn't moving it's going to have any noticable difference. I'd wager changing the main rad for an ali or copper version or tripple pass (if the pump could take the extra pressure) would give a much higher cooling effect than one very small extra rad.

Otherwise why do cars have radiator fans if the area is sufficient?

If this was the case then it would have been far easier for audi to put the aux rads infront of the main rad in terms of airflow and packaging however they didn't. The ones they did put in front are very wide and thin so as to not obscure the main rad as much as possible.

[00-Schneider]

Everybody is free in choice

Deinstalling wasn´t an option for me - reasons had been given. As far as the speed limit in the States is that rigid - i wouldn´t care about the aux rad at all.

In Germany, it´s a little different. We torture our cars

[00-Schneider]

Worth pointing out that the aux radiators are not actuive all the time but thermostat controlled.

Correct, but the thermostat is never completely closed - there´s always water flow in the aux rads - otherwhise you would have air in the system after changing the coolant.

Just check it out...drive afew minutes with normals revs...then stop and touch the aux rad...YES, it´s warm! The aux rad thermostats open at the same time than the one for the main rad.

IMHO, Audi calculated the needed rad surface for the V8 engine in the A4 B7. After they found out, that there´s not enough space to realise that surface on one single rad, they splitted it up to 3 rads in total.

Just my 2 cents...

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Worth pointing out that the aux radiators are not actuive all the time but thermostat controlled.

Correct, but the thermostat is never completely closed - there´s always water flow in the aux rads - otherwhise you would have air in the system after changing the coolant.

Fair point - I've been trying to find out more about the aux rad thermostats. The study guide is a bit vague on them.
If you change the coolant properly you wouldn't have air - you have to run the car to operating temp and refill anyway.

IMHO, Audi calculated the needed rad surface for the V8 engine in the A4 B7. After they found out, that there´s not enough space to realise that surface on one single rad, they splitted it up to 3 rads in total.

But that has to cover a wide set of operating conditions - say 46c ambient in Dubai for example with aircon on etc. One point is that the supercharged cars have been tested with one aux rad on the 'ring and have been fine and thats going to be alot harder than sitting at 155ish with great airflow and medium rpm.

[BlingBling]

Out of interest how many rads does the C5 S6 have?

[00-Schneider]

As long you drive and get enough airflow to the rads - no problem...even on the Ring.

But - and this is standard in Germany - imagine to push the car really hard for some time and then you´ll get stuck into traffic jam...then you´ll need the calculated rad surface to avoid head gasket failures.

Overheating isn´t a prob on the RS4, because the guys fitted this car with 3 rads - BUT it can get a problem, because the engine bay is fully packed and there´s only very little airflow.

The first thing is did on my car was removing the stupid anti-noise-mat under the hood...this senseless thing allows the engine even better to get really hot...

[PetrolDave]

I think what Dave was meaning that of course surface area is everything with radiators however one extra aux rad (which lets be honest, isn't that big or efficient and a good 1/3 of it is covered by the bumper vent anyway) isn't going to add sufficient surface area such that when the car isn't moving it's going to have any noticable difference.

That's exactly what I was pointing out.

Could the idea of restoring, or even increasing, the amount of cooling be looked at from the angle of increasing airflow through the radiator at slow sppeds? I'm thinking of a more efficient fan (i.e. a redesigned fan using the existing motor), or a faster fan motor, or increasing the underbonnet airflow by putting exit vents into the bonnet?

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I've tried looking for an aftermarket rad but no joy - fan would be the next choice.
Its interesting that I've seen many fan motors fail slowly but still look like they are working. Really need to measure the current the motor is drawing to make sure all is well.

Bonnet vents a bit 'Chavez' but can't deny a couple naca ducts would really make a difference to the under bonnet temp.
There isn't much room to put or rearrange stuff. Wheel arches are a good place to start as you can get good airflow utilising negative pressure pulling air through a rad.

[caldy]

I already have a Vorsteiner vented bonnet, including air scoop, and I'm not sure it does much to lower under bonnet temps. Having said that, following some spirited driving, you can see the hot air rising from the vents when stationary so perhaps the existing fan and vents are doing their job.