996.1 Wheel Liner, Brake Ducting, and Undertray Options

Hello Rennlisters, One of my front wheelwell liners is needing replacement, so it has led me down a rabbit hole of all the various options for improving the aero on our cars, but I am getting lost on the sheer number of choices. I know a lot of you track guys have experimented with this. This is was something I pursued with my E36 M3 and it paid dividends so want the same for my 996.1. I want something that is direct bolt on/plug and play. GT3 parts make sense but I am seeing people going for 997 or Turbo parts too. For what it is worth it's an aero kit car and I will be adding a center radiator. Stock 996.1 Carrera brakes. Here is what I have gathered so far. Can anyone confirm these will work and are the "best" option given my parameters? Undertray: ​​​​​​ 99650452902 - GT3 air duct for transmission Front wheel well liners: 99650412301 - 996 GT3 driver side wheel liner 99650412401 - 996 GT3 passenger side wheel liner Front brake ducts: (if you're crazy enough to run these on the street) 99634111790 - 996 GT3 Cup driver side front brake duct 99634111890 - 996 GT3 Cup passenger front brake ducts OR 99634111891 996 GT3 driver side front brake duct 99634111791 996 GT3 passenger front brake duct Rear Brake ducts: 99633112790 - 996 GT2 Left ​​​​​​99633112890 - 996 GT2 Right Would you change anything I have listed above?

Congrats on the project. It would definitely be interesting to get your analysis/observations on the differences between the original parts on the car and the replacement parts to answer the question if they actually provide a benefit. Sorry to say I never went thru the exercise other than adding 996 gt3 brake ducts. Appreciate the thread!

Sirhod im happy you are tackling this I want to replace and or improve my undertray aero as well maybe we can do a bit of group buy in I want everything you posted part#s so keep me in the loop please

Another question what are the differences on the front gt3 brake ducts?

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The GT3s are bigger and direct more air to the brakes for cooling. They fit in our 996s without any modification and are very cheap. Easy and cheap mod that's worth it.

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They actually do need to be modified with the meyle replacement arms. They are not as tapered as originals near the subframe mounting point. Besides the brake and maybe transmission duct I can't see any on that list that's going to make much difference except on a race car. Especially for the money.

The wheel well liners r 2 piece, there is also a part thats about $300 a side that clips to the cooling pipes to direct air. The parts can all be found on the autoatlanta site. If u r not tracking the car none of this is needed.

You can also get the GT3RS brake ducts which are even bigger. But they will need to be shaved down to fit. But unless you really think you have a brake cooling problem on the track, the gt3 ducts will do you fine. Just change your brake fluid after every track day and you will be in good shape.

No the difference I’m asking about is the front ducts because he has 2 listed one for the cup and the gt3 I was asking are they larger or just different shape

Don't know Mike. After messing with brakes and cooling for 20 years on the track, never felt I had to go with anything more than GT3 ducts because I never had any cooling problems. If I was club racing enduros, I would probably have them on my car. But the longest I am ever at at speed is about 25 min. You can go overkill with this stuff.

996 GT3 Cup (ECS has this listed as GT2...some research shows they are the same). I think the Cup/GT2 front brake ducts have a lower extension to feed more air over the rotor. Cup/GT2: Standard 996 GT3: Worth mentioning is they are about the same price...~$150 per side

I have the 6Cup front brake ducts. They drag over everything and the bottom gets ruined. Skip those and buy the 997 GT3 front brake ducts. They are 90% as good and are like $7 each. L - 997 341 483 92 R - 997 341 484 92

PLEASE oh PLEASE post pics of these when/if you get them. Better still, pictures comparing them to your stockers. I'm dying to know what the difference is between them.

Wow you aren't kidding....$5.07 from Getporscheparts. Direct bolt on?

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Yes to oem parts. Can you say cheap and easy?!

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Thanks but those are the brake ducts. I want wheel liner images.

interesting timing as I need to replace my front inner wheel liners. C4S if it makes any difference, I haven't researched it yet.

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That I will do. From my understanding the GT3 liners vent the air from behind the radiators into the wheel well/brakes instead of underneath the car. Presumably this would increase brake cooling and reduce lift. As De Jeeper mentioned there are other parts needed to make it work.

Ok so it seems like the 997 GT3 parts 99734148392 and 99734148492 are a no brainer for the Front Brake Ducts at $10 for the pair. Quick search shows they are direct bolt on. In that same search I did see in one very old thread that the 997 Turbo front brake ducts would also work and are larger. 99734148303 & 99734148402. These are still a lot cheaper than 996 GT2/3 ones at ~$60 for the pair. Anyone try these?

FWIW, some of you guys have wrenching skills. I don't. So a good exercise to go thru assuming your not a wrencher is to get under the car when its in for servicing under the lift, and ask them to walk you through the undertray, brake ducts, wheel liners, front bumper and rear, and ask them what enhancements they would suggest. If it's a seasoned porsche shop, they probably have a few other street and track oriented 996s including gt3s sitting around and they can point parts out to you. This is a very helpful exercise to go thru. The mistake I always make is not taking pictures.

Sirhod, See prf response. Unless you are fast as he'll and plan on tracking your car in a ball busting PCA Enduro race during a hot 100 degree day, you don't need them. Not telling you not to do it for the hell of it. But just saying that the GT3 brake ducts will be more than you will ever need on the street and a 25 min DE session. But as I said above, make sure you run fresh brake fluid every time you go out on the track with or without those big honking cup ducts.

U dont have to change fluid every track day if u put better fluid in. I run Endless 650 but most run Castrol srf. These will last u a season usually. Although i flush a few oz from the calipers every 12 track days just to be cautious. Only decent ducting pics i have.

Hope your airbag works.

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Watch out Aaron you may be accused of being on a budget or not being rich enough to maintain one of these cars.

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Its been removed so no issues there. My brakes have been and continue to be remarkable with zero fade. I have never had a single person in the race forum or at a de that recomends an every event brake fluid flush in a non race car, when using higher end fluid. The better fluid does require a full flush every year due to water absorbtion.

Hah I gotta get me some of that magic brake fluid!

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Yes it makes a difference. Your liners already include louvered sections to allow radiator air to vent directly into the wheel well. The louvers aim the air outwards so they're not the best for brake cooling, but as others have noted that is probably only an issue for track rats and racers.

I run RBF600 and I bleed a few ounces from each bleeder after every track day, probably 6 ounces total. I like to think that fluid that hasn't been heat cycled might have better performance. I also run the 7GT3 front brake ducts. So far I have not had any brake fade issues. I do have a set of 7Cup fender liners/brake ducts/air deflectors, just have not put them on yet. Don't be fooled by @De Jeeper 's front setup, that's the 996 RSR setup not the 996 GT3 setup. To use those 7Turbo front brake ducts you will need to make major mods to the front fender liners or you'll have to install 7Turbo front fender liners, which will be a project in itself.

Only the front uprights and break duct stainless shields attach to the uprights are rsr parts. The rest are regular 6-gt3 parts. I might put my street tires in tomor. If i do ill get some pics of the fender liners

Tons of great information, I appreciate all of your responses. That's what makes this forum great. For me, it looks like the front brake ducts from the 997 GT3 are the way to go at $10 per pair, but if money is no object the 996 GT3 Cup are bigger and offer more cooling. Next step I want to focus on wheel well liners. It looks like there are 2 iterations from the 996 GT3 presumably for 996.1 and 996.2. Parts diagram here: Wheel Well Liners , parts 99650412301/99650412401 and 99650412391/99650412491. Just researched it looks like 99650412391/99650412491 are the updated ones that do vent and say some posts about it lowering coolant temps too since air flows through the radiators better. In addition to the liners, it looks like the air guides that attaches to the coolant pipes would be useful: 99657523230 99657523130 These bastards are $192 per side. Ouch. The 997 version are much cheaper at $30 side ( 99757523191 & 99757523291)....but do they fit?

Bingo: https://rennlist.com/forums/996-foru...l#post14645541

I have the 997 air deflectors installed. They do not fit . Quite a bit of work is required to make them fit. May I ask, what are your goals here? With good pads (performance friction) and fluid (rbf600), and the 997 GT3 air deflectors, I have never had any hint of brake fade at time. Even after 30 minutes at a brake intensive track there is enough brake power to push R-comp tires into antilock action.

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WOW how did I miss that before. Differences I see between the stock fender liner and the 996 GT3 liner: There is a cutout in the GT3 liner along the inner edge; this allows radiator air to exit into the wheel well The lower radiator exit opening is closed off on the GT3 part The underside air channel for brake cooling is smaller in volume on the GT3 piece A followup post mentions additional heat in the frunk area compared to a standard C2. Mine already gets warm, not hot but noticeable. Maybe the additional frunk heat is why the 40AE and 997 direct air straight out the back of the radiators and then angle it out of the wheel well.

They vent straight back for better aero. The downward exit of the rads has long been reported to create lift.

More pics of mine. U can see the gt3 2 piece liner, air guide and the 997 turbo scoop. The back half of the gt3 liner looks just like the stock piece.