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Old 04-02-2018, 02:07 AM   #1
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Redirect airflow from center radiator

I have searched but not really found an answer so I go ahead and start a new thread..

Im switching the front bumper cover to the OEM Aerokit-2, aka 996 GT3. In my quest to improve front end stability I thought Ill go ahead and redirect the airflow from the center rad upwards.. So I have cut the 996GTR RS-slots and will close of the OEM slots at the underside.

Now comes the tricky par where Id love some advice..
Since Im not just after the cosmetics, I strive for a proper aero improvement however I do not want to "butcher" the car, I want a clean install, as OEM looking as possible. My first attempt was to go "Full GT2", I got the GT-2 chimney, however discovered since the GT2 approach pushes the front rad forward too much to fit the 986/986 narrow front, the moved center rad interferes with the ducts for the side radiators. My next attempt is to simply tilt the front radiator upwards which involves flipping it and DIY some simplified air duct behind the radiator.

Questions:
1) If I flip the radiator the inlet/outlet will be in the bottom, will this work or will there be air bubbles trapped in the radiator? If so can this radiator (996.106.037.51) be vented? It looks like it has some sealed outlets for venting, but I have no clue how to use them.

2) I know that I have seen pics of someone using the GT-2 chimney in a blue 986 and it looked really neat. I believe it can be used if trimmed so that the center rad don't need to be pushed too far forward. Anyone tried this?


The spring is around the corner and Im about to panic!!!



EDIT: Found the Blue 986 with GT2-chimney, but its on another forum, not sure if its ok to link to other forums.


Last edited by Robert986; 04-02-2018 at 03:05 AM.
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Old 04-02-2018, 02:46 AM   #2
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Does your wind tunnel have a moving floor?
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Old 04-02-2018, 03:05 AM   #3
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Does your wind tunnel have a moving floor?
Was that a serious question? If so please explain.

EDIT: Sorry Im slow.. I guess you question the aerodynamic idea? If so, Im no expert but as I understand it this is a pretty common mod that mimics the proven functionality of eg GT2. Anyway, Im already into it, getting all dirty so its not a question of IF, just how to.
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Old 04-02-2018, 04:23 AM   #4
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Im surprised youre struggling with front end stability, do you have a wing in the rear that is compromising the balance? If you want to improve front end stability a simple 4 splitter will do far more than playing with airflow in and out of the radiators. Keep in mind to that as you block air from passing underneath the car you will be reducing air that makes it to your brake ducts.
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Old 04-02-2018, 05:31 AM   #5
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Im surprised youre struggling with front end stability, do you have a wing in the rear that is compromising the balance? If you want to improve front end stability a simple 4 splitter will do far more than playing with airflow in and out of the radiators. Keep in mind to that as you block air from passing underneath the car you will be reducing air that makes it to your brake ducts.
I drive really really really fast... And I never brake.
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Old 04-02-2018, 05:49 AM   #6
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I shorten my question: Will it work to keep the center rad flipped? Or will I get a problem with air bubbles?
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Old 04-02-2018, 07:26 AM   #7
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um, i think you folks fail to recall that the base 986 came without a centre rad and spec racers have no issues with brake cooling.

and that when the centre rad was introduced on the 's' model, no additional aero was added. so, from an aero perspective, the addition of the centre rad on the 's' model provided front end lift on a car that previously did not have it - you are taking air approaching the car at a high velocity and redirecting it downwards. this will lift the front. worse, you are introducing air under the car which will lift the entire car.

assuming the 986 spent lots of time in the wind tunnel and was the epitome of porsche aero engineering, the hack addition of the third rad was an aero compromise to address heat management of a large engine in a confined space.

regardless, what is the worst that could happen from redirecting the air upwards? more front traction. worst case - the rear will feel lighter as a result. it will not be lighter, but will feel so comparetively. what to do? change how you drive, get wider rear rubber, whatever. if you are on a quest for performance, it is foolish to compromise one aspect of your car to accomodate inadequacies of another.

otherwise, there will be less air under the car = less lift overall. not a bad thing.

to the op - i think you can use the gt2 duct but would have to trim your side rad ducts a bit. otherwise, you can keep the centre rad in it's oem orientation and just push forward and tilt using threaded rod and spacers. i would like to see the link you are referencing; the one i am aware of is on the 6 speed forum and includes the install of the gt2 front bumper cover which has the taller/narrower side rad openings. and it is hard to copy the gt3 rs install as they didn't use the gt2 duct iirc.
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Old 04-02-2018, 11:05 AM   #8
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You are absolutely correct TRK!

When it comes to actual aero performance, I can say that at 150Mph it becomes REALLY light in the front, not very planted Id say. Besides the top vents Im also adding a decent splitter, I think it will be just about right. Pics will come when Im done! :-)

Regarding the other thread Im referring to, I hope Im allowed to share links to other forums, if not please let me know. Here is that thread anyway, there is a guy (jimk04) who has made a really neat installation, however I believe that its a bit too tight behind the rad, so I doubt its optimum from a aero perspective. http://www.planet-9.com/987-cayman-and-boxster-competition/208657-center-radiator-venting-holes-question.html#post2011233


TRK, you are correct, the GT2 duct can be fitted as intended if the side ducts are trimmed, to rough for my taste, wanna keep the side ducts neat and tidy.

Anybody with opinions on the tilted rad? Air bubbles or not?

Last edited by Robert986; 04-02-2018 at 11:12 AM.
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Old 04-02-2018, 11:30 AM   #9
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a couple of things from the planet 9 thread ...

he is using a 997 gt2 part; might get better fitment from the 996 gt2 part?

you also need the duct that mounts between the bumper cover and the centre rad (it is shorter and angled compared to ours); this may improve fitment also?

i actually have the parts but have yet to install them.
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Old 04-02-2018, 12:36 PM   #10
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Search for threads by j.fro, he has done what you are doing and explains it in a thread. I think he flipped and tilted the front rad, no issues with air bubbles from what I understand. Pics please!!
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Old 04-02-2018, 03:39 PM   #11
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I can report that at 140 my car is steady as a rock.
I did not turn the radiator upside down; I did flip the top radiator bracket around, and I added a section to make each hose longer to compensate for the extension. This effectively angled the center radiator forward. I put a piece of sheet metal behind the radiator to "chimney" the air through the top vents. I also sealed off the bottom of the bumper, forcing all of the air over the hood. The 986 rubber radiator-to-bumper seal would not work with my GT3 front bumper no matter whatI tried so i just left it out. All of the air isn't going through the radiator, but it's certainly going through the top vents. Cooling is fine, and the nose is pressed to the pavement.
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Old 04-02-2018, 03:52 PM   #12
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also, perhaps you can 'punch out' the side rad ducts with a heat gun? also note that, if you do use the gt2 part, you may need a spacer on the bumper mounts to move the bumper forward a bit to fit it all in. there is a gt2 part # for the spacer, but i am sure something could easily be fabricated.
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Old 04-03-2018, 01:51 PM   #13
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Re light front.....what is your ride height? Stock ride height and damping will feel very light and nervous at 150. Lowered on coil overs should help
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Old 04-04-2018, 06:24 AM   #14
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Wow, great inputs guys!

I like the J.fro approach to extend the hoses, I feel that a flipped radiator is asking for problems with trapped air in the radiator.

Btw. I Think that the 996 and 997 chimneys are the same parts: 996.575.325.30.
The splitter Im adding is the 99650598691, actually intended for the 996 Mk2, but I hope I can make it work.

Ill sure let you know how it turns out, right now Im busy replacing a side radiator that had a leak. The bumper cover is at the paint shop so soon I hope to have it all put together.

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Old 04-04-2018, 06:27 AM   #15
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Originally Posted by jaykay View Post
Re light front.....what is your ride height? Stock ride height and damping will feel very light and nervous at 150. Lowered on coil overs should help
Good point, Its on my list, however I try to do one thing at a time to trick myself to forget the cost for each step.. ;-) Also want to verify front clearence with the new splitter Before I decide on lowering.

Last edited by Robert986; 04-04-2018 at 06:33 AM.
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Old 04-04-2018, 06:31 AM   #16
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"you also need the duct that mounts between the bumper cover and the centre rad (it is shorter and angled compared to ours); this may improve fitment also?".
Good Point, I dont have that part, may I ask for the Part no if you have it?
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Old 04-04-2018, 06:37 AM   #17
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99657514130
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Old 04-05-2018, 12:35 AM   #18
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99657514130
Perfect, thanks!

Man, thats a pretty expensive piece of plastic..
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Old 05-26-2018, 05:40 AM   #19
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Ok boys, Im done and quite happy with there result..

I gave up on the GT2-duct, just could not make it fit the way I wanted. Instead I flipped the radiator, grinded a bit om the metal frame holding the radiator so it wont interfere with the side rad ducts. I found a "perfect" angle so I could reuse the original front duct.
I closed the outlet on the bottom with aluminium sheets. Well, here are the pics..

When flipping the radiator the OEM hoses do reach so no need to make it complicated and change hoses, I also learned that there is a valve for venting out the air after it is flipped (The blue one on pic-4).
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Last edited by Robert986; 05-27-2018 at 12:26 AM.
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Old 05-27-2018, 12:18 AM   #20
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Some more of the result..

And, yes.. the front is now a lot more planted in higher speed. I guess also the rather big splitter is a part of it.
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