Why does the rad behind the drivers-side fog light not vent into the wheel well?

[amz]

I was curious where the radiator behind the drivers-side fog light on my '12 S4 vented to so I took a peak behind wheel well liner and - nothing. There's a couple of inches separating the radiator and the flat surface of wheel well liner. As far as I can tell...the air enters through the fog light grill, goes through the radiator, and then has 2 paths: into the engine bay by going 90deg vertical, or taking a 90deg bend towards the passenger side...and then into the engine bay. Intuitively, adding a vent to the fender liner there should help airflow across the radiator and enhance its effectiveness, but I haven't heard of anyone doing this and I'm wondering why not? It seems like such a simple mod to do.

I did some searching and found a diagram which shows the supercharger cooling system, including this radiator, part #44 here:

Yep, it's connected to the electric pump that moves water through the intercoolers in the supercharger. Cesar and I went back and forth on this for a while, till he supplied this great blow-out diagram.

http://img.photobucket.com/albums/v668/Ookane/Coolingsystem_zpsca8bf134.png

[Silverbullet S4]

Interesting. I haven't looked but couldn't you just cut some vents into the liner and call it a day?

[IanCH]

Why would it need to vent into the wheel well? it gets an enormous amount of airflow coming in, I'm sure its not starved for flow. Why would you risk damaging the rad by cutting a vent?

[bhvrdr]

We used to do this all the time in the B5 and B6 A4 days. The B5 S4 used to come direct from the factory with vented fender liners. Some people modded them in to get more airflow.

http://www.audiworld.com/tech/wheel8.shtml

Mike

[amz]

Interesting. I haven't looked but couldn't you just cut some vents into the liner and call it a day?
This is what I'm proposing, just wondering why in the 6 years the platform has been out, nobody else has thought of it. I'm by far not the smartest man on the forums :)


Why would it need to vent into the wheel well? it gets an enormous amount of airflow coming in, I'm sure its not starved for flow. Why would you risk damaging the rad by cutting a vent?
How would it damage the rad? Take measurements of where the rad is, remove the fender liner, cut + install the vent, and you're good to go, no harm done to the rad.


We used to do this all the time in the B5 and B6 A4 days. The B5 S4 used to come direct from the factory with vented fender liners. Some people modded them in to get more airflow.

http://www.audiworld.com/tech/wheel8.shtml

Mike

Oh, nice! Was there ever any problems with ice building up or rocks somehow getting flung at the back of the radiator through the wheel-well vent? I wouldn't imagine either case to be a problem. If ice builds up in the winter, then we're back to where we started with the air hitting a stark wall. The downward-angle of the radiator vents would make it hard for rocks to get flung at the radiator unless you're in reverse, in which case they shouldn't have much force to begin with.

edit: all I need is the vent piece and I'm off to the races with this mod. Any ideas on where to get just the vent, or a similar-looking vent? Part #8D0 821 171 G seems to be the entire liner.

[anerbe]

I really don't know the underhood flow paths to understand how much air the small radiator gets with the factory air path. I also don't know how much pressure is built up in the wheel wells during driving.

Worth a shot, but from what I understand, wheel wells in general are a higher pressure area due to no exit vents and high velocity air travelling outside the wheel. Venting a radiator out thru the wheel well might not be effective if there is high pressure / low velocity air in the wheel well. It depends car to car.

In my previous 335i, it had an oil cooler with a vent at one of the wheel wells. The vent was on the passenger side, with the louvers facing outwards. This was how the car was developed - designed with a path to the wheel well. As you can see, the oil cooler is right in front of the wheel well. Venting to the wheel well could have been a case of only option due to packaging constraints.

http://billswebspace.com/BMW335VKMOilCoolerInstallation_files/image031.jpg

On the S4, the secondary Rad definitely has some air path present by not venting to the wheel well - the heat exchanger is developed with the stock airflow as a parameter. Would it be better thru the wheel well? Maybe so, and Audi wanted to avoid additional parts with a duct and vent to the wheel well vs an A4. Or maybe not - the air path is better stock.

Only one way to find out - try it. All I know from my past work in Powertrain Cooling is that all cars are different, and there's definitely a reason why the Rad is not vented to the wheel well.

[ride1157]

I agree with anerbe. There is a reason why there is no vent. There is a specified flow path there for a reason, that air flow could be used to cool something further in the engine compartment. OR they did not want to waste money on modifying the wheel liner as it is more than likely a carryover part from the original A4. You can always try and see what happens. Just be sure to put some sort of protection there from sand/rock spray. I personally would leave it alone, these cars barley heat soak compared to previous generations.