Improve cooling, behind the radiator?

Hi, I've have just replaced my radiators with full aluminium once, new low temp thermostat and then new coolant. Just right now cleaning out the A/C coolers, but they seams rather clean already. My temps where still rather high(just below the line between 80 and 120, thus around 100 degrees C) during modest hard driving the other day. While doing this cleaning I've been looking at how the air is ducted behind the radiator. It makes a sharp turn 90 deg to the ground, seams rather inefficient with lots of resistance. After spending some time thinking how to improve it (blow straight back in to the wheel well) I went and had a look if something already have been done by Porsche them self. On the 997 c2s I found that this approach (wenting out to the wheel well) was already made. SO, have anyone tried implementing this on a 996?? Using the 997 wheel liner and 'duct-behind-fan' ?

there's a how-to on pelican to do exactly that.

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996 C4S has the wheel well air exhaust too...at least on my 05 C4S.

Thanks, nice to avoid re-inveting the wheel. Found the pelican article: https://www.pelicanparts.com/techart...ell_Liners.htm

yeah. i looked hard at re-purposing oem parts to achieve the same result. the 9x7 cars all have vented liners. also i think some of the later wide cars (gt3, turbo, etc.) but was uncertain how the liners from one of those would fit into a standard 9x6. not just a cooling benefit either; better to dump air into the wheel wells (and over the brakes) than under the car and create lift.

I've been at the car looking around. I think a good solution would be: -Remove the inner duct -Make a big hole in the liner -Block the original exit towards the ground By blocking the original exit you are drawing more air thru the radiator. I don't think the internal duct is necessary since the space is already rather air tight. Then maybe add some netting to the hole in the liner, to prevent debris from piling up behind the radiator.

exactly how i thought to do it as well. don't see the need for the inner duct at all, nor for any special trimming of the liner - just cut out a big section and put some mesh in (worried about the wheel throwing a rock though a rad). then watch engine temps; air pressure in the wheel well might serve to oppose airflow across the rad which might be a reason to keep the bottom duct open (but i doubt it).

https://rennlist.com/forums/996-foru...to-reduce.html From 2016...

I have fender liners from a turbo for my C2.

You can do all that, but 100C is just fine; not hot at all.

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that thread grew some legs from last time i saw it! cool; proof the oem parts are backwards compatible. now i gotta spend more $.

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Did this require any trimming or modification to work?

Ok, so I went ahead and did this modification. I took away the deflector shroud behind the fan and I cut away some of the wheel liner closest to the tub. See picture. I found in the other thread that this was the contemporary GT3 solution. I did not cover the old hole towards the ground. I unfortunately did no data collection before/after so this is just my observation, all temps in C. My last drive was in 20 degree ambient(coolant getting close to 110, all fans running full speed), this was at 10 ambient. I made a similar drive (serpentine road climbing 600m i short time) which loads the engine properly and keeps speed down. A/C off at both drives. Result? The temperature needle is like glued at 80 degrees! Using the OBD reader the temp during the drive was never over 90 degrees, mostly at 80-85, which is rather impressive. Lower temp also gives a higher oil pressure, roughly 1.6 at idle. My full list of service/modification on the cooling system for completetion: -New full alu radiator -New coolant -New thermostat, 72 degrees (Brand: Wahler) -Cut hole in wheel liner -Removed deflector shroud behind radiator fan -Cleaned out A/C radiator When the weather heats up I will have another go to have more of an apples to apples comparison. Original vs modified

The problem of cooling is not cooling capacity with higher driving speeds. In these conditions cooling capacity is abundant. So I doubt it will have an effect on better cooling. Allthough better streamlining of the air can never be a problem

My 03 stayed cooler way better at 85 in 95 degree weather than at 50 in 70 degree weather..

Yes, exactly. I�ve found my bone stock 996 to have barely adequate cooling at speeds 45mph and below. It�s a question of airflow for sure, because 45mph and below requires little power.

Did an apples to apples comparison today. Same road, same driving, same ambient temperature. With clean A/C radiator and the mod, temp is a good 10 degrees C lower. I stopped at the top of the pass as first time and non of the fans was running, last time all fans was running at full speed incl the engine bay fan. Idle oil pressure was higher and the temp needle indicating a good 10 degrees C lower. During the drive the engine only passed above 90 degrees C on the steep serpentine road where speed is low and engine load high. Rest of the time it stayed like glued at the 80 degrees mark.