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911R style diffuser for 996s and 997s?

 
Old 12-29-2016, 08:18 AM
  #16  
rs10
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Originally Posted by 808Bill View Post
^^ That's it. I would think a chin splitter combined with lower the car would give better results,no? After all they are light up front.
A chin spoiler is the clear easy win for the front, but I'm looking for a solution for the back. By all accounts, Porsche has been careful to more or less balance front and rear lift downforce for good reason, so I'd like to do the same. And for various reasons, touched on above, I'm not sure a wing or just a ducktail would be ideal for me.

Last edited by rs10; 12-29-2016 at 03:17 PM.
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Old 12-29-2016, 03:16 PM
  #17  
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Originally Posted by The Radium King View Post
pelican has a how-to on how to vent your two side rads into the wheel wells instead of downwards. note that this was done on the gt3 rs cars and introduced by porsche into all the 997 cars. 6 speed has a how-to on how to install gt2 ducts onto a car to vent the centre rad upwards.
Interesting. Venting downwards is generally bad, but then, so is more air entering the wheel wells. The 911R got huge aero benefits by adding wheel well vents to get the air out. And I has heard this was done on GT3s, but I thought it was for brake cooling. Are you sure it helps the GT3s with lift and/or drag? Or has this mod been well tested on Carreras?
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Old 12-29-2016, 03:43 PM
  #18  
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pressure analysis of wheel wells shows highest pressure in the upper front quadrant of a wheel well. if you look at where the dp cars, sport racers (and yes, 991 gt3) vent their fenders, this is where it happens. a cool thing if you can do it, as it converts lift to down force.

if the air isn't vented then it exits the fender in around that area - look at how water exits your fender when driving down the hwy in the rain. out the side is better than down and underneath.

the gt3 rs guys took holesaws to their fender liners to vent the rads into the wheel wells, they called it brake cooling because most regs don't allow aero mods but they do allow cooling mods. the gt3 rsr completely re-did the rad layout to vent out the side instead of downwards. the gt2 and i think the turbos, as well as the 9x7 cars, all vent to the wheel wells.

the third radiator venting upwards showed up on the gt3 rs and the gt2. i can't recall where i got the info from, but the excellent handling of the gt3 rs was attibuted in large part to this upwards venting of the third rad. again, now it is pretty common on the porsche track-oriented cars. they don't do it to their street cars as it takes away from the understeer engineered into the chassis (porsche have been afraid of oversteer since the 930 litigation days).
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Old 12-29-2016, 03:51 PM
  #19  
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I could use more down force, I often drive 70+ on the highway
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Old 12-29-2016, 09:53 PM
  #20  
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Originally Posted by The Radium King View Post
pressure analysis of wheel wells shows highest pressure in the upper front quadrant of a wheel well. if you look at where the dp cars, sport racers (and yes, 991 gt3) vent their fenders, this is where it happens. a cool thing if you can do it, as it converts lift to down force.

if the air isn't vented then it exits the fender in around that area - look at how water exits your fender when driving down the hwy in the rain. out the side is better than down and underneath.

the gt3 rs guys took holesaws to their fender liners to vent the rads into the wheel wells, they called it brake cooling because most regs don't allow aero mods but they do allow cooling mods. the gt3 rsr completely re-did the rad layout to vent out the side instead of downwards. the gt2 and i think the turbos, as well as the 9x7 cars, all vent to the wheel wells.

the third radiator venting upwards showed up on the gt3 rs and the gt2. i can't recall where i got the info from, but the excellent handling of the gt3 rs was attibuted in large part to this upwards venting of the third rad. again, now it is pretty common on the porsche track-oriented cars. they don't do it to their street cars as it takes away from the understeer engineered into the chassis (porsche have been afraid of oversteer since the 930 litigation days).
Thanks for the very helpful info!

One interesting note about the third radiator venting upwards. I thought so too re. the RS's handling. But according to SportAuto, this only reduces lift by 3kg at 200 km/h. Still, that may in fact have been a significant benefit, as otherwise it would have almost as much front lift as a Carrera due to the huge rear wing pushing the front up.
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Old 12-30-2016, 10:10 PM
  #21  
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Originally Posted by The Radium King View Post
pressure analysis of wheel wells shows highest pressure in the upper front quadrant of a wheel well. if you look at where the dp cars, sport racers (and yes, 991 gt3) vent their fenders, this is where it happens. a cool thing if you can do it, as it converts lift to down force.

if the air isn't vented then it exits the fender in around that area - look at how water exits your fender when driving down the hwy in the rain. out the side is better than down and underneath.

the gt3 rs guys took holesaws to their fender liners to vent the rads into the wheel wells, they called it brake cooling because most regs don't allow aero mods but they do allow cooling mods. the gt3 rsr completely re-did the rad layout to vent out the side instead of downwards. the gt2 and i think the turbos, as well as the 9x7 cars, all vent to the wheel wells.

the third radiator venting upwards showed up on the gt3 rs and the gt2. i can't recall where i got the info from, but the excellent handling of the gt3 rs was attibuted in large part to this upwards venting of the third rad. again, now it is pretty common on the porsche track-oriented cars. they don't do it to their street cars as it takes away from the understeer engineered into the chassis (porsche have been afraid of oversteer since the 930 litigation days).
This mod is something I'd definitely like to know more about, and I don't want to highjack the thread (even if I started it), so I started a new one: https://rennlist.com/forums/996-foru...l#post13847239
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Old 01-17-2017, 06:26 PM
  #22  
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Seems I was right that it doesn't cost much to make the 991R diffuser. Suncoast is selling them for 991 GT3s for just $560. Here's a link with good pictures:
http://www.suncoastparts.com/product/SKUGT3DIFF.html

Surely there's a market for something like that for our cars!
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Old 01-17-2017, 10:35 PM
  #23  
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Man, I would have probably destroyed that thing last track season.

I have the skid plate below my 3/4qt deep oil pan and its got a million nicks and scrapes.




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Old 01-18-2017, 09:33 AM
  #24  
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I ordered one to try to fit to my 996. I don't have have a deep sump but, I do plan to run one.
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Old 01-18-2017, 07:31 PM
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Originally Posted by trendy996 View Post
I ordered one to try to fit to my 996. I don't have have a deep sump but, I do plan to run one.
You ordered a 991R diffuser to fit on a 996?

If so, please keep us posted!
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Old 01-19-2017, 08:24 AM
  #26  
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Just received it yesterday and this thing is very stout! It's a lot more rigid than I had expected. Going to look how I'm going to go about mounting it this weekend.
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Old 01-20-2017, 06:20 PM
  #27  
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Originally Posted by trendy996 View Post
Just received it yesterday and this thing is very stout! It's a lot more rigid than I had expected. Going to look how I'm going to go about mounting it this weekend.
Thanks for the keeping us posted! If I may ask a few questions to follow up on your initial report: When you say it's rigid, is that just the undertray, or the fins too? And if the fins, do they bend at all?

And as for stout, do you mean heavy? In any case, it would de great it you could weigh it and let us know!

Thanks again!
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Old 01-20-2017, 09:20 PM
  #28  
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One good speed bump and it's done...
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Old 02-18-2017, 03:39 PM
  #29  
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Both. It's as thick as the oem 996 sump pan guard Porsche offers. I believe the 911r metal is steel. I never magnet tested it but, guessing by the weight. Both the fins and undertray are stout/thick. The tray is metal and the fins a think hard plastic. The fins do not bend.

I used the oem 996 sump guard to mount the 911r diffuser. In the picture I have it hard mounted. Will prob add more mounting points soon but, need to get my gas filled for my welder to weld brackets/mounting tabs for the other hole locations on the 911r diffuser. The rear bumper is a demon speed gt3 rep. The deck lid is a 996 cup lid with 996 uprights trimmed and welded to fit a 991 gt3 wing. In the front I'm running a 996.2 gt3 front bumper fitted for a 996.1 with a joe toth splitter. Going to add his fender foils to help eliminate the trapped air in the wheel wells.

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Ps don't worry she's going to the paint shop to have the front paint matched better, rear bumper painted and a solid roof skin put on.

Last edited by trendy996; 02-18-2017 at 04:59 PM.
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Old 02-21-2017, 05:45 PM
  #30  
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Originally Posted by trendy996 View Post
Both. It's as thick as the oem 996 sump pan guard Porsche offers. I believe the 911r metal is steel. I never magnet tested it but, guessing by the weight. Both the fins and undertray are stout/thick. The tray is metal and the fins a think hard plastic. The fins do not bend.

I used the oem 996 sump guard to mount the 911r diffuser. In the picture I have it hard mounted. Will prob add more mounting points soon but, need to get my gas filled for my welder to weld brackets/mounting tabs for the other hole locations on the 911r diffuser. The rear bumper is a demon speed gt3 rep. The deck lid is a 996 cup lid with 996 uprights trimmed and welded to fit a 991 gt3 wing. In the front I'm running a 996.2 gt3 front bumper fitted for a 996.1 with a joe toth splitter. Going to add his fender foils to help eliminate the trapped air in the wheel wells.

Ps don't worry she's going to the paint shop to have the front paint matched better, rear bumper painted and a solid roof skin put on.
So you attached it to the sump pan guard? Or you just used the sump pan guard mounting points?

And any rough idea how much it weighs? Sounds like at least several times more than the sump pan guard, no? (Which I think weighs 2 kg, but I seem to recall it's aluminum.)
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