Which front bumper & spoiler (for aero, cooling, performance, etc.)?

Looks like I need to replace the front bumper of my 996 C2. There seem to be 3 or 4 main options: normal, aero kit, GT3 (same as aero kit?), and C4S/40AE/Turbo (plus slight variations, like between C4S and Turbo, and also different lip spoiler options). Anyone have any info on how these compare regarding lift/downforce, drag, and cooling? I know it�s important that the lift/downforce of the front end is a good match for the rear. While my rear is currently stock, I�m tempted to modify it. I�d consider a big GT3 or aero kit style wing. But for weight and other reasons, I�d also consider something less aggressive, like a duck tail similar to that on the 997 GTS or a low, small fixed wing like on the 996 Turbo S. Any insight into what front bumpers (and lip spoilers) would be a good match for such rear options? Thanks!

maybe try GT3 setup, although I dont think there would be any noticable performance advantage in any front or rear bumpers, GT2 and 3 were factory performance designs, so.... You will have to use what fits a narrow body instead of widebodys or look at aftermarket kits

If cooling is the primary consideration, go with a front bumper (or mod yours) to install the center radiator. As you said, mismatching the front aero and the spoiler might not be a great plan. I personally love the MKI GT3 wing - I think it makes the 996 look amazing. But I'm obviously biased...that's the reason I bought the car.

You can get an oil cooler front rad if you do the piping right. A couple places sell them. You need to put an adaptor on the oil cooler (engine side). The cooler is the same as the heat exchanger.

If I'm trying to decide bewtween the normal and C4S/Turbo/40AE bumpers, I see cooling as the main plus of the latter. Howevre, in another thread it was mentioned that the C4S has Turbo radiators - so perhaps the bumper shape alone doesn't help ... . Does anyone know if the 40AE has Turbo radiators? (If not, then clearly the bumper alone helps. (Because 40AEs, like C4S's, don't need 3rd radiators with X51 engines, unlike C2s and C4s.)) On the other hand, I suppose the C4S/Turbo/40 AE radiator creates more drag. Does anyone know how much? Or looked at another way, how much in the C4S's drop in top speed versus the C2 from 177 to 174 mph (or from 285 to 280 km/h) is due to the front bumper? (I'd expect it to have a bigger aerodynamic effect that any of the other aerodynamic changes (fatter hips, slightly bigger rear spoiler, wider rear tires with a wider track, so less shielded from wind by the front tires). On the other hand, not sure it would have a bigger impact than mechanical drag from the 4wd.) Anyone know about this? Thanks!

And then there's the question how normal and C4S front bumpers compare to the GT3 and aero kit front bumpers (or are they they same)? I have no idea.

Quotes source post: 12698543

Yes RS 40AEs are equipped with the Turbo radiators. And with regards to your drag question I seriously doubt you'll see much of a difference amongst bumpers... I mean seriously if you're going at +170 mph on a regular basis at sustained speeds I can guarantee you the last thing in your mind will be how much extra drag is the bumper + radiator combo producing... Just saying...

Quotes source post: 12698911

Thanks. Just to be sure I'm not missing the importance of 2 letters, is there an "RS 40 AE" that is different from a 40AE? Thanks again!

Quotes source post: 12698911

Yeah, I imagine it seems like a trivial concern. My situation may be a bit different though, and it's not just about top speed. I regularly drive long distances on lightly trafficked autobahns, and it's above 120 mph (200 kmph) that you really feel that the 996 is faster in a straight line than my last car, and I don't want to give that up. But you don't feel it with the C4S. Reviews when it was introduced said you did feel the weaker top end, and it's true. Of course, you also feel how the C4S handles, which is great, but I doubt the front bumper contributes much to that.

So it's starting to look like how much air reaches the radiators may not be a key criteria for bumper selection. Can't be sure, but it seems the key functional differences will be drag and impact on lift/downforce. Now if only I could find out how these four bumper styles differ. I've done a bit of searching and will try more. Googling too I suppose. But if anyone knows, it would be greatly appreciated! Needn't be in terms of kg at X mph, by the way. What I do know is that the C4S has half the front end lift of the C2, and the Turbo has zero - and most/all of that is due to the bumpers and spoilers. But I don't know the drag impact. And I've no clue how the GT3 and aero kit compare ...

Quotes source posts: 12699601, 12700542

I meant to say "rs10" instead of "RS"... And there's only one type of 40AE. For full aero balance you must be looking at the entire aero package not just the front end. The front is the first line of attack, it slices and distributes airflow through the vehicle, and tries to maintain high pressure air from going underneath the vehicle, the mirrors also play a role in the laminar flow, and how air will be distributed on the side and towards the back of the vehicle, and then you have the back of the vehicle, where the wing plays and important role at many levels, to continue providing laminar air flow while minimizing turbulence behind vehicle, providing downforce and rear stability as speeds are ever increasing. With that in mind probably what you're looking for in terms of best aero package is more like the GT3, nice clean front bumper, side skirts (also to minimize high pressure air from going under car) , and beautiful rear wing. Just a thought. Maybe this linky helps? https://www.carthrottle.com/post/eng...-of-race-cars/

I just went through an old article in Excellence about the C4S. Seems the C4S bumper sends 8% more air to the radiators. Even assuming all that air made it to the smaller radiators on a C2, I guess that does not make a big difference. If one wants to do something about heat issues, one needs to do more. If one wants to choose the ideal bumper, drag and lift are probably bigger issues (unless one would consider switching to the larger C4S radiators). And one should be cautious about a bumper designed to send air to different shaped radiators - unless (one can be confident that) the C4S/Turbo style bumpers sold for C2s somehow solve that.

Quotes source post: 12701362

Yeah, I have been thinking that GT3 aero add ons probably make more sense for our cars. The Turbo bumper was presumably designed to produce more cooling at the expense of drag. (Not lift - both the 996.2 GT3 and the Turbo have zero lift. Surprising the GT3 doesn't have less lift/more downforce at the rear, considering its much more prominent wing. Maybe the Turbo side scoops slow air passing above the car ... .) And the C4S bumper was presumably designed to well, look like the Turbo, with a bit less contribution to downforce and drag. I'm sure it would be hard to find a more aerodynamically efficient bumper for a C2 than either the standard one or the GT3 bumper or look-alike aerokit bumper. I don't think many (any?) tuners do a lot of wind-tunnel testing. Maybe an immitation 997 bumper ... . The issue is the drag/lift compromise. Porsche could have put an aerokit on all C2s. Either they didn't just so they could charge extra for the option, or they thought that for a car less powerful than a GT3, it's better to sacrifice some lift for less drag. (Except for people who spend a lot of time on track and/or who just like how the aerokit looks.) Presumably this is also the reason why they didn't give the C4S the full Turbo aero treatment. (It has roughly half the C2's lift, both front and rear, versus the Turbo's zero.) And if I don't want to go with a GT3/aerokit rear wing, then I may end up with a disbalance between front and rear lift. (I'm tempted, but I'm also tempted by ducktails, which seem the lowest weight solution. No clue about the aero properties of a ducktail, but I guess they do less to reduce lift than a wing, otherwise GT3s would have them.)

Anyone know how much a GT3 or aerokit bumper (or entire aero package) reduces the top speed of a C2? Thanks!

Lol, at everyone worrying about top end, extra weight, and drag for a street car. None of the options listed are going to affect either of those variables significantly. Do you really drive your car that fast on the street? Even on the track, you won't come close to hitting the top end unless you are on the Mulsanne Straight. I'd bet you wouldn't notice the drag or weight difference with any of the above listed combinations even on the track. However you would notice the added down force if you went with something like the GT3 wing. I say go with what you think looks the best.

Well, again, as per my post above (number 9), my situation may be a bit different. Whatever it is that slows down the C4S at high speed (whether aerodynamic drag or mechanical drag) does matter to me - based not on theory, but on experience. If I were focused on how it drives on track, I'd go the GT3 without giving it a second thought - but I'm mainly focused on how it drives on the road.

I'm pretty sure it's more mechanical drag that makes the C4S slower on the top end. AWD has a lot more parasitic drag than any of the subtle differences in aero between the listed bumpers. Even a GT3 wing wouldn't affect top end that much. From my experience with aero on my S2000 race car (different splitter lengths, GT wing at different AOA, underpanels) it will not affect your top end that much. You would have to be running data acquisition on a track to notice the difference imo. The most noticeable effect is downforce with a proper wing and/or splitter. Even in your case (hitting high speeds on the Autobahn) downforce is a more welcome benefit than less drag. Sure, it's primary benefit is increased corner speeds but even on a long straight stretch of highway extra downforce will make you feel much more comfortable at speed. You will have more confidence in the car and be able to sustain higher speeds for longer periods of time. It is a benefit you will feel even in a straight line at speed.

Per your situation, I'd go with the GT3 aero. Even that is not really extreme but it is a good balance between street / track or in your case, high speed highway runs. Proper GT air foils will put a stock GT3 wing to shame in regards to downforce and less drag. I wouldn't want to run that big a wing on the street though Edit: Actually go with the GT2 wing. I think it looks better - sleek and not as high as the GT3 wing.

i was looking for a bumper that would send more air to the rear breaks. I often taken curvy roads at high speeds all while trail braking. This causes my pads to heat up beyond belief.

Quotes source post: 12720024

Are your pads fading? I wouldn't rely on a bumper to send air to rear brakes. The proper way to do it is with brake ducts. I think that is overkill on the street though. I'd just go with a little more aggressive compound if you are fading your current pads.

I was also thinking that the main thing that slows the C4S down is mechanical drag from the 4wd. Then I realized how I could find out - check the official top speeds of aerodynamically identical C2s and C4s. Much to my surprise, my source gives the same top speed for the 3.4 liter C2 and C4 (280 kmph, or 174 mph), and the same speeds for the 3.6 liter C2 and C4 (285 kmph, or 177 mph) (although there was no 3.6 liter C4 in the US, there was in Europe). So much to my surprise, in fact, that I don't fully believe it. I found this on autoscout24.de. Tomorrow, if I remember, I'll check check the owner's manual in the car. I remember it includes performance data for all 3.6 liter, non Mezzger 996s.

Anyone know what the GT3 rear bumper vents vent? Brakes? Wheel wells? Muffler heat? I found myself with nothing to do while standing next to a 997 GT3 RS today, and I took a close look at the side vents in the rear bumpers. And although the car was parked on a light floor in a reasonably well lit place, peer though I might, I could not detect the slightest glimmer of light coming through them. Surely Porsche wouldn't put fake vents on a GT3 RS, would they?

Quotes source post: 12723272

On second thought, I may have forgotten something. Can't the 996 4wd system direct all torque to the rear wheels? And if so, wouldn't there then be no extra drag? Perhaps the entire drive train for the front wheels disengages. Or perhaps most/all of it keep turning, driven by the front wheels themselves, but turning mass alone isn't drag? Rather, it's like a heavier flywheel, or heavier wheels, which dent acceleration, but not top speed?

Factory aero,Third radiator kit.Accusump,and a Motorsport AOS,you should be covered for cooling and oil starvation........all it takes is a few $$$$...LOL....good luck.

Quotes source post: 12720024

That's probably your traction control. It uses your brakes. High speed curvy road trail braking will get it going crazy. You can't fully defeat it with the push of a button.

Quotes source post: 12725467

Thanks for your post, including the pictures - well there's certainly no doubt that the factory aero kit looks good! Does it make any significant contribution re. cooling? Also, did it come with the car, or did you add it? And if you added it, did you notice any effect on high speed acceleration? Above 120, for instance? Thanks!

Quotes source posts: 12723272, 12723507

I thought I should update my hypothesis here, because it isn't quite right. On a C4S, and I'm pretty sure on a C4 as well, at least 5% of power always goes to the front wheels. So whatever impact 4wd has on mechanical drag or inertia, it's always there. Still, given that the C4 has the same top speed as the C2, it still seems that aerodynamics plays a big role in the C4S's weaker top end.

Quotes source post: 12818912

Why not just stay with the regular factory front bumper? I assume you have not experienced any overheating issues currently? If you have not then the stock setup is doing just fine. Don't fix it if it ain't broke. About the only modification I would advise would be to add the 3rd radiator but many cars get along just fine with the 2 radiators. By keeping with the setup the car came with you don't have to worry about upsetting the balance by installing an overly aggressive front bumper then trying to come up with a suitable replacement at the rear to regain the balance. BTW, regarding the AWD system and the 5% torque minimum to the front axle is theoretical. In the real world it can be 0% to something around 5%. Standard allowable deviations due to normal manufacturing tolerances probably account for the difference. FWIW, my reference has the 40% (max.) coming in at around 150mph.

So it is sending 40% of torque to the front wheels at 150? Wow, that would be a surprise; I'd have thought it would send it there to help acceleration at low speeds, then back off at high speeds. This could explain why a C4S has noticeably less acceleration at high speeds than a C2 - provided the same is true of a C4. (I presume the C4 and C4S have the same drivetrain.) (As I may have mentioned (last visited this thread a while ago), while the 3.6 liter was not sold in the US, it did exist in Europe, probably elsewhere too.)

Quotes source post: 12819820

Undobtedly good advice, and based on what I've learned, I would not change the bumper just for cooling. But since I have to replace it anyway, and since I would not mind C4S or even 996.2 GT3 level lift/downforce if the speed penalty is small (and I can accelerate better than a C4S at high speed), I'm hoping there might be a solution that works for me (for both the front and the rear). As for the 3rd radiator, I'm kind of inclined to pursue other options as I cam across a post saying there is a "well documented" increase in drag (though no more details than that, and I haven't done any searches related to this topic). Also, it adds a bit of weight. Maybe lift too? (No idea.) So I'd lean towards other options, like waterless coolant, maybe a low temperature thermostat, and not doing too many laps in a row.