rs10

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!

OKB

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

5CHN3LL

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.

Sneaky Pete

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.

rs10

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!

rs10

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.

Fast40th

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...

rs10

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!

rs10

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.

rs10

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 ...

Fast40th

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/

rs10

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.

rs10

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.)

rs10

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

Thanks!

WynnS123

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.