Question: 996 center radiator vent mod

I'm in the process of modifying my SP996 to vent the center radiator airflow out of the top of the bumper ala Cup/GT3 style. So far I've sealed off the openings on the bottom of the front bumper and I've cut and modified the top vents already. The center radiator has long been installed and I'm just going to use the "inversion" technique and flip it top to bottom so as not to need any hose extensions as I've seen documented elsewhere on this site. I did have one more question I couldn't find documented anywhere specific to the 996. What duct is needed to attach to the back of the radiator to channel the air out of the top vent? I've seen some people list a 997 part and some also use the top duct from the 996 GT2. What's the best solution for the 996 with the standard/non-GT3 radiator part? Thanks in advance.

Subscribed as I am going to be doing this soon to my Boxster as well.

I have read a lot on this modification and the general gist I got was that the 996 GT2 chimney/vent seemed to be the best. I have had all the parts for a while but hope to finally get around to this at the end of the month. Obviously turning the radiator upside down and turning the frame/bracket around will be key to minimizing additional changes. The only thing I am unsure about is the duct for the front radiator as clearly with it pushed forward at an angle I cannot see how the OEM 996 GT3 duct will fit. I am just wondering if a 996 GT2 duct will work. I am not sure how different the central opening on the front PU on a GT2 is. Pip

It was recommended to me to fab one out of thin sheet metal or aluminum from the Home Depot HVAC section.

Unfortunately us British are less prone to modifications and when we do make them we err towards OEM parts. I already have the GT2 chimney so I am not going to knock up something else now. Good luck with your DiY job. Pip

It seems the Brits may need some Yankee ingenuity ? I thought they were avid diy guys(Mulberry harbors ,Spitfires etc) and it was the Germans who cringe at our mods? Maybe EU influence is more insidious than we thought? :-). Now back to the Hvac mod please.

At the end of the day, all you are doing is channeling air a few inches with the ducting. And flipping the center rad bracket isn't that simple. I tested it last time I had the front end apart and it needs some additional modification as well.

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Me too.

I put the center rad in, and I didn't use the duct from the center snorkel below the license bracket. I'm getting plenty of air flow across there. The duct only fits one way, and it's pretty obvious. I just didn't see the need so left it off.

We are talking about ducting the air out the top of the bumper RSR style for additional downforce.

Aside from the GT3 upward duct, isn't there two piece duct work for the front and rear center rads that are on 996 cars like the Turbo? Seems like I remember seeing that on the parts breakdown for the Turbo with center radiator.

I just installed the center rad on my'99 - only one piece of extra duct-work to install. It goes behind the bumper cover and in front of the radiator.

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Thanks. Unless that air channel is pretty smooth, I don't think you'll see much/any gain. I believe you will develop a pressure bubble just in front of the center rad that way, unless the plenum size increases behind the rad, and then smoothly exits out the top. It's the old problem of not having wind tunnel testing to check airflows. All I can say is the adiabatic temp rise behind the rad is going to produce a pressure bubble somewhere unless it is sized, and channeled right.

Great point. I'm skeptical about its advantages but admittedly have no wind tunnel or aero testing experience. However, the fact that it is currently channeled to add lift and can be changed fairly easily to add some downforce makes me think it's worth trying.

My Ferrari cooling has the air enter radiation just above the front spoiler, and the rad is canted forward about 25deg. Then, there's a big air channel behind the rad, two fans drawing, and it all goes up and out the louvers in front of the front trunk area. The louvers and the air channel is from the left inner headlight bucket, all the way over to the right inner headlight bucket. Of course, I don't have side rads, but that exit channel is - as they say, heuuuuuuugggee. Or perhaps, 'bigly'. Lots of hot air comes flowing out of there.

Just like Rennlist!

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Oh no, do not get me wrong we do love little 'Heath Robinson' affairs mainly because we do not have the US style throw loads of money at it solutions available. The writing implement in space story highlights it all. The British would have gone with the Russian solution. More specifically though within the GT and RS family the British definitely love OEM. You certainly would not find 'spinners' on the hubs or chrome wheels. We are generally quite staid. In short non OEM parts or modifications should be removed and sold separately to maximise return on selling a GT3 or RS. Pip

" we do not have the US style throw loads of money at it solutions " we said : Home Depot HVAC parts - that is nickels and dimes money. "the British definitely love OEM. You certainly would not find 'spinners' on the hubs or chrome wheels" where did we propose that ? Such disparagement may be a little counter-productive for a Brit with 4 posts on an American Forum ?