fastech

Hi all,

I'm toying with the idea of a 996 C4S for the new Road Tire class (using SCCA Stock class prep rules). Front is seriously limited on available camber, maxed out at about .7 deg. Someone along the way mentioned they thought there was a factory bulletin allowing some sort of adjustable or shimmed control arms (possibly the GT3 ones) to gain camber (for crash repair, but for my uses it would allow me to get what I need for autocross purposes). For those of you familiar with SCCA stock prep rules, it needs to be in the factory repair manual or an official service bulletin. Does anyone know if such a document or guideline actually exists? I'd need to be able to substantiate its legality in case of protest. Can anyone here help?

Thanks guys!

Brian Flanagan

NJ-GT

If you already have the 996C4S, you cannot get more negative camber from other adjustments, as the strut stops is the only adjustment available in that car. So, remove all the negative camber from the back, reduce toe-in from the back, install a bigger rear adjustable sway bar, put the biggest tire you can fit in the front, and don't use the biggest tire that fits in the rear.

The PAX for AS would make you a mid-pack runner, because AS is supposedly faster than BS and CS (softer paxes), but the reality is that these classes are faster.

If you don't have the 996C4S, don't get it if you intend to autoX it seriously. On the limits of grip, the AWD 996 and 997.1 send torque to the open-diff front axle to avoid any minimum slip angle, promoting even more understeer. A RWD 911, or a Boxster/Cayman are better tools for autoX.

fastech

Thanks for the reply. I've got the front camber all the way in (.7 deg), toe slightly out, the rear camber pulled to about 1 degree neg, toe at just barely in from zero, can't remember the exact number, but just enough to be able to be aggressive with the throttle. I'm running 245/40 RS3's up front, 285/35's in the rear. Don't want to put any wider than 245 on the narrow front rims as street tires don't respond well to over-tiring the rim. I've debated whether to go with a big front or big rear sway bar. Rear is of course the conventional wisdom to cure push, but enlarging the front would help preserve the minimal camber and may ultimately work better. Testing would be in order to answer that question I think.

RTA competition is mainly Evo & STi (BS pax) and WRX (DS pax). My gut feeling is that those are all pretty nose heavy and even more short on camber than the C4S in stock trim. The STi and Evos are also-rans in BS. The WRX is a strong contender in DS and definitely has a softer PAX, but I feel like the C4S can compete on index. I may be way off- it wouldn't be the first time. But I think it will be an interesting experiment at the least.

Anyway, just trying to stack the deck in my favor as much as possible, by looking for any advantage, such as trying to find more front camber. If anyone has any more tricks that might help, feel free to throw them my way!

-Brian

burglar

I'm more commenting to keep track of this, as I think it's a very cool idea to run the 4S in RTA. I can't help with the control arm question.

Anecdotally, I'd guess that a bigger rear bar would help mostly on turn in, where a bigger rear wouldn't show up until mid corner. I also don't know how big you can go in the back until you start hurting ability to put down power on corner exit. I'd at least start by picking the one that matches the majority of the courses in your area - slalom courses like front bar, sweeper courses like rear.

Not sure how much this would help as I've never tried it, but perhaps you can play with the offset allowance to widen the front track / narrow the rear to reduce understeer?

fastech

I'm not so concerned with courses in my area, it's more important to me to be effective on national event courses. First big event will be the Dixie Match Tour (assuming the car passes muster at some T&T's), which is typically a transition-heavy course. Unfortunately, there's no competition signed up yet, and I'm not sure running unapposed will tell me much. Hopefully RTA will get some more entries over the next few weeks!

Ultimately I think I'll need to test with some fancy adjustable shocks, different bumpstops, front and rear sways (one at a time of course), and different alignment specs, but I'm reluctant to spend a lot of money on the project until I have a feel for whether or not it has a prayer nationally. Guess we shall see.

Also, I have a bad, bad case of automotive A.D.D., so it's all subject to change, lol...

NJ-GT

Lost battle at National level.

DS WRX has the lead by a huge margin, but it is nice to see a 996 C4S on the grid.

The biggest problem is the understeer caused by any slight slide on the rear end, removing power from the wheels with traction, and sending traction to the front, horrible implementation. The C4S and 996TT have the worse understeer I have experienced in the 986/987/996/997. This cannot be corrected.

You can apply the 0.975 index to your Dixie PAX and see where you stand compared to AS/BS/CS/DS/ES/FS. I anticipate a decent gap.

fastech

Well that's not very encouraging! Guess I'll see how it feels at the T&T Sunday. I ran a private track day at TGPR Thursday (a pretty tight track) and it was definitely pushy in the tighter corners. Adjusting my corner entry and exit strategies helped somewhat, but I don't know if it will translate well to autocross. We shall see!

My other possible choice is a C5 Z06, and it's stupid fun on track or autocross course, but on the road, it's so...Chevy. <shudder>

NJ-GT

If it pushes at a racetrack, it will push more at an autoX. Your alignment is spot on, almost the same I used for my Cayman in AS, 0 toe all around, max front camber, min rear camber, and the Cayman doesn't push as the 996C4S, it doesn't have the odd torque transfer on medium slip angles either.

The C5Z06 is a great performance car, but I agree, uninspiring when driven on public roads, horrible interior, boring to look at, and feels numb. However, it is the most reliable and the most performance for the money today. It is competitive in SS, it is competitive in NASA-TT3, fun DE car.

Good Porsche options for RT classes: NONE.

Upper Mid-Pack options for RT classes: CS 2004 Boxster 2.7

Street tires tend to equalize performance in cars. For instance, I would run my Cayman on street tires and my Fiat on street tires (RE11 on both), and their performance was similar at an autoX, then on A6 the Cayman would gain 1+ second, while the Fiat would gain 4+ secs.

The good Porsches for RT are in SS, but the PAX is based on r-comp tires performance, so no much help there, the PAX kills them.

The Porsche Boxster in CS is a good RT option, CS has a soft PAX, and this Boxster can run on super fat 18" tires.

BS and CS have almost the same pax. A 2009 Boxster 2.9 with LSD would be better for RT than a 3.4 Cayman/Boxster S, but these two cars cannot overcome the PAX advantage of a CS Boxster (almost 200 lbs lighter on the same tires).

For the price of a C4S, I would rather get a 2005 Carrera S, 40Hp more, more torque from the 3.8, better looking, and 100 lbs lighter. Not competitive in RT, but competitive in ASP.