I'm getting hooked on Auto-x...

[93Rubie]

For better or for worse, I ran my first ever event in mid August, I just did my 4th one last Saturday. It is a ton of fun, and I am learning a LOT, both about the car and me. Kinda of funny but the more I use my Corvette in motorsports and drive it too, the more I really love this car. It proves itself over and over again as being one of the best sports cars in the world. If not THE best. FYI, I think I held my own in B-stock against folks with MUCH more experience in their S2000's and Boxsters. We all where in the tire class=street tires so that evened things up a bit. The course was fast and open. Something my first 3 times at auto-x the courses where extremely tight by comparison. My best was 43.8. The others best in the low 40.XXX bracket. I did beat a fellow rookie in his 08-present Subaru WRX STI. Nice to see a 18 year old sports car kicking new machinery to the curb. I can tell looking back where I lost speed and what I did wrong. The car has SO much more speed in it. Needs a better driver...:eyerole Less hamfisted inputs and throttle applications...:ugh and more smooth. I was lower mid-pack with my PAX times. Closer to mid-pack than the bottom.

To get to the point of my post, I have been studying the SCCA rule book for Stock classes, C4's are in B-Stock. It allows some room for mods but very little. I intend to stick to B-Stock because...A: It will take quite a while before I get to where I can outperform the car. Even a C4 has very high limits and performance potential. B: It is cheaper... C: Since I drive, show, race, etc...this car closer to stock the easier to maintain and live with.

That being said, my 93 has the FX3 suspension, I can run the Z07 setup as it was an option on my car. Since mine does not have Z07 I will have to piece it together. From the 92-95 Z07 setup which was the same all those years according to our C4 Suspension Chart. I already have the rear 24mm sway bar and the FX3 setup. I need the the below:

1. Front 92-95 Z07 spring 90.1 (n/mm) FSK spring code
2. Rear 85-95 Z51, Z07, R9G spring 57.2 (n/mm) NYU spring code
3. 30mm Front Sway Bar 85-95 Z51,Z07,R9G
4. HD Lower Control Arm Bushings

I think that is all. The rear spring NYU and the 30mm bar should be easy to find. The front spring and lower bushing, a bit harder.
Would the 88-91 Base front spring at FHA 93.1 (n/mm) be an acceptable alternative to the Z07's FSK, they are very similar.
Also, other than finding low mileage good condition lower control arms from a 92-95 Z07 car, is there an aftermarket alternative or even maybe the lower control arms from a Z51 88-91, 96 car?

I'm not sure on the early 85-87 Z51 30mm front bar fitting on the later suspension? I don't think they would. I know the rear spring should be compatible from 84-96, fit wise.

Also, since I have the FX3, lets say I get a Z07 setup under my car, would it be worth while to add stiffer Moroca valving to the Bilstien shocks? Also, would a FX3 Motor sports Controller be a good idea, or would these parts or a combination thereof, make the otherwise good Z07 setup too stiff for good handling. Lets face it, too stiff and instead of absorbing bumps mid-corner in a parking lot, you go skittering off because the suspension cannot absorb the hits and bonces too much.

 

[93Rubie]

Might have to nix that last part, rules say any replacements have to "standard parts". So re-valved and stiffer controlled shocks did not come from the factory so...maybe not. I don't intend to ever reach any kind of level that might affect regional or national things for the SCCA. Still I intend to stay within the rules as best I understand them.

I better get rid of that cut air lid, I doubt anyone cares...not any kind of real advantage.

 

[radar1]

Might have to nix that last part, rules say any replacements have to "standard parts". So re-valved and stiffer controlled shocks did not come from the factory so...maybe not. I don't intend to ever reach any kind of level that might affect regional or national things for the SCCA. Still I intend to stay within the rules as best I understand them.

I better get rid of that cut air lid, I doubt anyone cares...not any kind of real advantage.

I have 95 ZO-7 and it handles very good ,the only thing I don't like are the FX-shocks at high speed on the track feels funny I also have a 96 LT-4 base one and build the sup. myself and I love it all stock to the C-4.. Well maybe not the front bar it's 32mm S. 1 1/8 I don't know if vett went that big or not has F. spring 88-91 FHA... F/rate 93.1 RPO FE-7 or FX3-A......... and rear spring NYU R/rate 57.2 RPO FE7 28mm S. bar in the back..Stock heavy Duty shocks the yellow ones.. and some very sticky tires all new bushing front and rear No poly.. Handles like race car runs on the track with some newer one also..Rides a little ruff on the road .. This is a good place to start and the aligment has to be right or the C-4 will not handle right I use the the Advanced street one works for me.. Front toe 0.. Camber .25neg.. Caster 5-7... Rear toe 1/8 camber .50neg ..Good luck...

 

[Tuna]

AutoCross can be addictive!

Years ago when I auto-xed with my FX3 92 Vette, I bought an autocross controller for the FX3 shocks that allowed me to dial in stiffer setting at low speed. I think that helped a lot. The controller I had was made by Bilstein and it looked just like the factory original controller so the tech inspection folks couldn't tell the difference unless they opend the box - which they never did. Bilstein also did a road course controller that allowed me to dial in less or more grip in the front or rear by just changing the shock settings. The controllers can be swapped out quickly enough so that street driving and race driving are not compromised.

Btw, I also installed the Moroca valved shocks - good for racing but a real bitch on the streets.

Braided brake lines would be nice along with speed bleeders.

There used to be a company called R-D Racing that had some good stuff to make the C4 handle better and a nice harness bar and a chassis bar that tighened up things a bit but when I google them, I get garbage now.

Anyway, Enjoy the fun of autocrossing and buy stock in a tire company! :L

 

[Hib Halverson]

The HD lower control arm bushings were never serviced nor were the control arms themselves. The only way a car got the HD bushings was at the factory in control arms which are stamped "Z51". When they were available, the only service replacements were arms with base bushings.

You're right on the springs and bars.

Whatever you do, replace those parts as a package not as onesy-twosy.

For street/track on alignment you first need to have all suspension parts in at least good condition and excellent or new is better. Next you need to take all the shims off the front spring and move all the shims on the rear spring to below the spring. Then set:

-0.5 camber at all four corners.
as much front caster as you can get with that camber setting
zero to 1/16 toe-in front.
1/16-in toe-in per side at the rear.

if you're track only, you can jack the camber way up...at least -1.0, all the way around to start then use tire temps to dial it in more.

 

[catbert]

I autocrossed for many many years, and had more than my share of success - mostly in C4s, and I'll only give you one piece of advice, and it's probably the same as other experienced racers would give. Learn how to get everything your present set-up allows out of your C4 before you even think about mods. If the car runs well, the brakes are effective, and the suspension is in great shape, just run the hell out of it until you skills catch up with the potential of the car. That can take a short time - or a long time. When you are competitive for a class trophy, it's time to work on the car. It's far easier to learn when you are going a tad slower than the experienced class hot shoes. That said, pay attention to alignment as was said earlier in the thread. Have a BALL!

 

[Yoda]

I will echo what catbert says

I did my share of auto cross (NCCC) back in the 70's and early 80's... Auto Cross is NOT a Drag Strip NEVER Brake IN a corner be set up before the pylons or corner, if everyone is running stock then their brake lights work, watch where folks are braking for obstetrical then judge you driving skills (Time) and soon you'll be the one being watched...

One of the best things is throw those hammer grip hands away and be as SMOOTH as silk and Finesse the car through the course, brute speed only matters on the straight aways

Compare speeds from different classes, you might be surprised that the difference's are not all that great don't out drive you vision...

most of all ENJOY

Bud

 

[radar1]

The HD lower control arm bushings were never serviced nor were the control arms themselves. The only way a car got the HD bushings was at the factory in control arms which are stamped "Z51". When they were available, the only service replacements were arms with base bushings.

You're right on the springs and bars.

Whatever you do, replace those parts as a package not as onesy-twosy.

For street/track on alignment you first need to have all suspension parts in at least good condition and excellent or new is better. Next you need to take all the shims off the front spring and move all the shims on the rear spring to below the spring. Then set:

-0.5 camber at all four corners.
as much front caster as you can get with that camber setting
zero to 1/16 toe-in front.
1/16-in toe-in per side at the rear.

if you're track only, you can jack the camber way up...at least -1.0, all the way around to start then use tire temps to dial it in more.

I used your chart to rework my 96 and boy did it come out great..I looked for a LT-4 with no OPPs. and was hard to find found one and put on lift and removed all from under the car...Read and asked called for 90 days and came up with what I have now..What I wanted was a NOS 96 C-4 that would do it all very good and I think I came up with it.. Took 6 mo. to fine NOS parts did it ..put it back like a watch ..Ok the test .... Can't out run a friends 05-ZO-6 to the turn one on a track we run on but a car leanth from him on other side and can pass most C-5s 335whhp LT-4 and drive to the 7-11... Brakes play a big part in the way it handles C-5s on f. stanless lines Hawk pads all new stuff.. Price for rework 96 C-4 $7-10,000 boy is it fun ..run with the big dogs look new drives new and the look on there faces when I pull up beside them $60.000 ZO-6s PRICELESS..

 

[93Rubie]

Holy Thread revival Batman!!!

Yeah, I know my Corvette is WAY faster than my car. The plan is to leave it very stock for now until I catch up with the car. I'm WAY behind.

For the time being I'm going to lock in alignment similar to the one Hib suggest for auto-x/street use. This is NOT a race car but a street/dragstrip/auto-x queen. SO a compromise is needed. Right now everything is working fine and nothing is too worn out to work correctly. I'm going to piece together the Z07 setup and make all may changes to the car down the road.

Hib, why switch the shims around on the spring? Does it change the spring rate or who it flexes? I cannot change ride height for SCCA Stock classes.

Catbert, your right and I realized this very quickly, learn what you have, then modify later. You'll get more out of the mods if you can drive first. Applies to drag strip as well.

Yeah, Tuna, I've thought about that controller, use the FX3 to your advantage. Besides the rule book states shocks are free, but if you have electronically controlled shocks you have to use the standard shocks. Says nothing about how they might be controlled!!!! At least not specifically. FYI, for stock classes (SCCA-Solo 2) for 2012 you can change front sway bar OR rear sway bar, before it was front only. Now you can choose which one to change.

 

[fastglass95]

AutoCross can be addictive!

I dis-agree, I've been autocrossing for 15 years and I can quit anytime I want!

You may want to look into some NCCC autocrossing, I'm not sure where you are located, but then you are running against nothing but Vettes. And you can learn a whole lot from some of the other drivers, such as alignments, tire pressures, tire types, brake pads / rotors, etc....,

The National Council of Corvette Clubs, Inc. ~ NCCC will get you to the National page, scroll down to very bottom for Region pages.