tjZ06

Okay, so I'm looking a few years down the road here (2-3 years at least). I'm happy racing my Z06 in OSP as a true street car for now. And I don't have the space or money for a truck 'n trailer at this point anyway.

But I figure if I keep AutoXing as seriously as I have been the last 2 years a) I'm going to want to fall into a Nationaly contested class b) the level of prep to get my car where I want it to be time-wise is going to make it less and less of a street car c) the wear/tear/damage of AutoXing 2 or 3 dozen events a year will begin to catch up with the car.

Right now my car is SM2 legal (as far as I can tell) but I just don't run it there. At about 3200lbs and on stock springs and shocks its just never going to compete with a car like Andy's (never mind that I am nowhere near ready to compete with him as a driver). That's how things will stay for a while being that I'm just not ready to start gutting this car, run -4 degrees Camber, and put Aero parts on it.

In 2-3 years though if I decide to stick with the Z06 I think I'll be ready to make those sorts of moves. But is it worth it? Can a C5 ever really compete with the likes of the SM2 RX7s?

Looking at the new weight rules RWD is set at 1600lbs + 200lbs/liter. I see nothing in the rules about penalties for boost, or special exceptions for rotaries (since they function as twice the displacement). As such a SM2 RX7 would have a theoretical minimum weight of 1860lbs (1600lbs RWD base + 200lbs * 1.3L). Clearly they aren't going to make that minimum weight, so it’s not even a concern. But if I had to guess the competitive RX7s are somewhere around 2400lbs?

Now at my current 5.7L my car would have a 2740lbs min. weight. Within the SM2 rules I'm not sure that you can get a C5 that light.

A realistic weight of 2900lbs (still 250lbs lighter than stock, about 300lbs lighter than my car w/ its bigger radiator, oil cooler, some dynamat etc) would allow for 6.5L displacement. With a 6.5L L92 based motor 600RWHP would be pretty darn easy, with huge torque. On raw power to weight ratio I think a C5 can do fine, but hooking it up is a whole other story. Most SM2 cars are going to be on the same 335 A6s and there is only so much grip available for acceleration. A weight/rwhp ratio of 5 in a 2400lbs RX7 is going to hook up and accelerate better than a weight/rwhp ratio of 5 in a 2900lbs C5. The actual HP number itself in the RX7 will be much lower and shouldn't overpower the tires as easily.

As we all know, weight doesn't just effect acceleration. Of course weight hurts braking, transition, and ultimate grip. Again, figure most SM2 cars are going to be on 315/335 A6s the amount of grip generated by the tire is what it is across the board (obviously assuming the cars are utilizing the tires equally). But when that amount of grip has to hold 500lbs more (2900lbs C5 vs. 2400lbs RX7) the actual cornering capability would be much lower. Not to mention getting that extra 500lbs moving side-to-side in transition.

What do you think; will a C5 have a fighting chance in SM2 if I’m willing to go rather hardcore with it?

-TJ

TedDBere

Depends.

Can a C5 beat Andy or Erik? Maybe. Let's see how Junior's ASP times compare to Andy's and Erik's these next two weeks now that his car is better set up this year.

I co-drove Adam Breakey's stock C5 Z06 in SM2 in last year's ProSolo against both Andy and Erik. Adam finished 4th overall, so you can be competitive in the class with even a stock C5Z if you're a great driver. Can you win it with a prepped C5Z...maybe.

But I'm not sure the RX7 is the only car you should be worried about. How about the GT2 and Elise/Exige. Someone will eventually prep those and they may be the cars to have in SM2.

Mojave

Erik is a hell of a driver (when the car runs that is). I seem to remember pushing it on the trailer at the Houston Tour this year when the trans started puking fluid out the bottom.

redtopz

Hey TJ, thanks for that ride in your vette at Castle. Big difference from my gto Hopefully I'll be joining the c5z06 gang pretty soon. You going to Castle on the 30th?

Bill.

0ATI Performance

The answer a couple years ago was yes. Today with the SM2 rule changes favoring the turbo cars (RX7's) and unknown future of the class I don't know.

The SM2 C5 Corvette below could have won. It was built to the limits of the SM2 rules in 2005. Due to some unforunate personal issues, neither I nor my co-driver Danny Popp could make it to SCCA Nationals so we will never know... We did run the car elsewhere and it proved very fast. Danny always had a big grin after driving it...

Should you decide to pursue SM2 all out, be prepared to spend lots of time and money on development (and broken parts), be prepared to go slower before you go faster as you get it all figured out, and be aware that the SM2 rules are currently in a state of flux and more "take-backs" are lurking on the horizon. Take-backs suck.

It was a battle I chose to stop fighting this year for a number of reasons, one being after experiencing 3rd and 4th gear in the car on a road course........yea, baby!

Bob

97C5inSD

ATI i sent you a pm

XPC5R

Re-read the weight formulas for the rotary cars, they have to weigh in the 2500-2700lb range depending on the # of rotors. The drivers of those cars make them as fast as the prep does. The biggest advantage those cars have is their size, they are narrow and have a shorter wheelbase. Erik's car is on 285's and 315's BTW.

The C5 can be competitive I think. My XP car runs with or goes faster than those cars when driver and car are on song. While mine is light, I carry a lot of weight up high with the cage, and have a mild motor and auto trans, stock suspension geometry (just coilovers), and run on DOT tires.

Weight wise, our '01 ZO6 ASP car weighed in the high 2800's with stock seats. Low 2800's are possible. Use aftermarket traction control, and they make 345 rear tires now. You don't need crazy power, you do need the best suspension you can afford, and run all the rubber you can put down. (315 front, 335-345 rear). Run the car as low as possible too.

Now drive to the advantages of the car - namely acceleration off the line and the corners (watch Raftracer some time for a tutorial), cornering grip (we have a lower CG - which means less weight transfer), braking power (longer wheelbase, lower CG). The only place the car is noticeably slower is slaloms.

I run against cars all smaller and lighter than me, and have rarely felt held back by the car - driver runs out of talent more often.

TedDBere

Bob, I liked that car so much when you and Danny ran in the DC Pro that I went out and bought one. Does your wife still have the ASP car?

0ATI Performance

Yep, we still have that car. We finally had it painted this year so it is all one color now (originally electron blue). Blue Corvettes are faster!

We will still autocross that car closer to home, but with the new 20lb seat weight rule it will not be ASP legal in 2008 (which also applies to SM2 for all those looking to shave weight - forget about the seats).

Here is the latest picture:


Good luck at Nationals!

Bob

0ATI Performance

Right. So the Corvette being longer and wider needs some type of other advantage to be competitive (drivers being equal), especially in the tighter and speed-maintenance based course designs (where the braking and acceleration don't matter, and the Corvette is too fat to throw around).

Those RX7's (Mckee and Strelnieks) weigh in around 2500-2600 lbs. You can get an SM2 Corvette near 2800lbs, but it is a big effort, and much of that is being taken away with recent rule changes for the sake of "cost". Been there done that.

Also with the new weight rules, the amount of power you can make per unit weight is much higher for a turbo engine (1.4L adder) than with displacement. I had even threatened to put a turbo Ecotec in my Corvette, but that would have been silly.

Yea there is only so much power you can get to the ground, TODAY. That increases each year with improved tire technology. SM2 is a long term investment (for most people) so you need to think what might happen to the class several years out before digging the money pit....

Bob

MySR71

I've seen Bob's SM2 car at his shop and at a few events. I think it is the nicest C5 I have ever seen. The World Challenge pieces, the color, and wheels really make it look nice. Oh yah, it is fast too.