RX744CSP

iTrader: (4)

I'm running a '79 RX7 in autocross; it's a dedicated race car. For weight reasons, rather than go with CSP prep, I went with IT prep (can remove more weight and more suspension mods allowed).

Since it's IT prepped, I have to run 13x7's with Kumho Victoracers (IT doesn't allow for wheel diameter upgrades). I'm using Ground Control camber plates and coil overs on the front with 350 inch pound springs, and 175 inch pound springs on the rear, with poly bushings all through, Tokico Illuminas full stiff on the front and #3 on the rear. I'm still using the stock Watts link on the rear and the stock sway bars front and rear. I have an understeer problem when under power, which then turns to an oversteer problem in real fast slaloms.

I'm wondering if anyone else out there is running a similar setup, and has encountered this, and if so what helped or corrected the problem. Ground Control sez I've done it all correctly, and have no recommendations for sway bars etc.


Any suggestions? TIA.

Rx7carl

My first suggestion is to ask you to go to my site and read the rear suspension write up there. Poly in the rear is not a good idea in these cars.

So its plowing comming out of corners? Have you tried different camber settings? Taken tire temps right after a run? Getting your pressures and camber settings right is needed before you fool around with other stuff. If you dont have a pyro, then at least chalk the tires and read the tread after a run.

Umrswimr

Sounds like you have a weight transfer problem... Maybe a stiffer rear spring?
I'm not familiar with the exact setup for 1st gens, but I would suggest IM'ing rx7gslse. He has a first gen that seems to handle exceptionally well.

RX744CSP

iTrader: (4)

Good info on your site, RX7Carl. I am using Energy Suspension poly bushings on the rear, the upper and lower link bushings are 3 piece: a hard center piece with two soft outers. The Watts bushings, IIRC, are two piece and the same material all through. I have plenty of extra Watts link stuff, I'm going to do your modification.

I had a guy do my alignment for me, and spec'ed 3.5 degrees negative camber and 3.5 degrees caster (suggested by Ground Control). I went back through my stuff, and discovered that with the camber maxed I had only 2.6 degrees negative according to the printout. I guess he was trying to keep me from wearing tires. I've trimmed out the upper strut tower for additional camber, and will try it again.

rhinor61

Did CSP rules changed recently to allow modification to the upper strut tower metal. Meaning is slotting the strut tower allowed?


John

RX744CSP

iTrader: (4)

You are correct, SP (as set forth in the Solo II rule book) does not allow strut tower modification. If the car is prepped to IT rules as set forth in the GCR, then it can run in its respective Street Prepared class. You can run any modifications legal in IT but not in SP, and IT allows strut tower modification. The car has to be prepped either IT or SP; you can't pick and choose modifications from each class to come up with a hybrid. If it's IT prepped but used only for autocross, you don't have to have a logbook.

It cuts both ways; for instance SP allows any wheel/tire size, but IT allows only the same OE wheel diameter. I went with IT prep because I could gut the interior, saving a lot of weight, there are additional suspension modifications allowed (like spherical bearings) and the car can be used for dual purposes- I can run Solo I or Solo II one weekend, and the next weekend go IT racing with minimal changes.

'85 GSL 302

Geez, I'm was running like 5.5 caster at first. I guess that explains my difficulty steering. I'm running a very similar set up except I have much softer rear springs. I run about 2 degree's of camber, but with 4.7 degrees of caster. I have a touch of understeer through corners. Mine should be corectible with some stiffer rear springs. I also have the WATT's link, but with sphearicle bushings on the lateral arms, and stock rubber in the control arms. My car has supper pridictable oversteer, I love it.

I might try knocking the caster down when I get my second car and see if that helps my steering. Currently you need to be a 500lbs Gorilla to turn my car without power steering.

RotaryAXer

iTrader: (4)

So does this mean that you need to have the cage and all fo the safety stuff required for IT ie. battery kill switch, fire bottle and a few other things???

I think it does.

I am just curious....How much does your car weigh prepped to the IT rules? I doubt you gain that much with all of the other stuff required by the IT rules.

RX744CSP

iTrader: (4)

That's correct, it has to have all the IT bits like cage and firebottle, etc. SP allows substitution of only the drivers' seat, IT allows removal of any seats other than the drivers' seat. You can remove all the interior panels except the dash, and remove the sound deadener, etc which isn't allowed in SP. I have not weighed my car since gutting it, but I know for sure the seats, carpet, headliner, trim panels, sound deadener, and sound system weighed more than the cage! Adding a race seat allowed me to put 210 pounds of talking ballast about 3" lower in the car, too.

On the list for future removal: headlight motors, bumper shocks, hood bracing, hood latch, rear glass latch, and possibly gutting the drivers' door (to do this will require NASCAR type door bars, though).

RotaryAXer

iTrader: (4)

Maybe this is how I can get my weight down then. My closest competitor in my region is 200# less than me. (86 MR2) He has about 40 less hp though. I have no more money to put into the car this year though.

Lt. Dan

Bringing back to the top....

What are my fellow first gen autoxers running for front toe?

Dan

APEXL8T

0 toe to 1/16 out, 4-5+ castor, 1.0 neg camber...its been a long time since i had the 1st for the cones. I think it s close to this.

rob81gsl

iTrader: (3)

i'm running 4 1/2 degrees castor, 2.5 camber, 1/16 toe out. 400lb front springs 275 rear springs, but i'm also running that g force panhard bar and tri-link in the back as well which will make a huge difference in the set-up. i'm still fine tuning this set up but so far has done really well it's been a front runner in CSP and lapping fd's at lapping events

hope some of this helps