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Prepping my CSP car for next season (a little long)

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Prepping my CSP car for next season (a little long)

Old 10-23-03, 07:50 PM
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Prepping my CSP car for next season (a little long)

I just picked up an 88 GTU that has proven dominant in auto-xes near here (2 year class champ in the local events). Now, I'm going to be racing the car next season in CSP. The car is relatively setup and feels decent (haven't slapped on the race rubber yet). The car is mechanically very solid (replaced nearly all suspension components, engine has 20k on rebuild) and has some goodies (KYB AGX w/Eibach pro-rate springs, TII brakes/sway bars, single exhaust (very torquey), victoracers with a little life). I'm looking at getting the car ready over the winter to compete strongly next year (there's some performers out here in CSP).

I'm looking to upgrade the suspension more than anything else (of course). The plans are to pick up GC coilovers with race springs and camber/caster plates. My problem is in deciding on spring rates at this point. I need suggestions on a good starting point (375/275, somewhere in there?). Also, is there anything else I should worry seriously about in terms of suspension? I'm planning to go to poly bushings but other than that, the coil overs appear to be my finishing point (strut tower braces needed? sway bars needed?).
Rims/Tires - This is a problem for me. I like that I have plenty of stock rims around to throw a set of race tires on but I also know that I can get better performance buying a new set of wheels. So, I've been looking at diamond racing wheels. I'd like to go to a 7 or 7.5 inch rim and 14 or 15 diameter, but this is a topic that I need assitance with. I also do not know where to begin in determining the desired offset to run. Ideas/suggestions please.

Thanks to all who can help out in this area and please refrain from saying "learn how to drive before buying stuff". FWIW I raced last season in a FP 1st gen (I couldn't handle the quirks of this beast for another season) and in a stock 2nd gen the season before that (as a novice). Aside from this, I am a primary driver for the University of Washington Formula SAE team. Driving skill is not what I'm asking about in this thread.

Appreciate it. -Redwood
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Old 10-24-03, 09:51 AM
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I like torque to squirt of corners in auto-x, and since a rotary has very little, comparison wise, try to stick to as small a diameter as possible that is feasible. As you know, the smaller diameter will give you a lower gear ratio(numerically higher). I am a proponnent of smaller diameter than some 18" monster that is simply not needed on 1st and second gens anyway for auto-x.
As far as wheels go, Diamond or Kosei's are good and cheap wheels, though the Kosei's to me look a little better. One thing to think about on offset is the Dave point. While you have to make sure that your wheel/tire do not try to occupy the same space as your strut, keeping the center of the tire in the middle of the steering axis will greatly help. The Dave point, taken from Dave Coleman of Sport Compact Car, is the point in tire where the steering axis passes through. This is explained a lot better is some back issues of SCC, but is something to consider.
All in all, for CSP, good tires in a probably 225-245 in a 14 or 15" will work beautifully. Also 15's I believe are handy for being to be able to pick some up at some races from ITS guys.

Also, a good lightweight flywheel and clutch combo will GREATLY benefit the 7. We have an extreme setup, 3 lb flywheel and 7 lb twin disk tilton, but the moment of inertia is tremendously low. tach up to 7 grand, in neutral, and back to idle in time it takes you to move your foot on the throttle. great for engine braking on course and also is a lot easier to rev match. In the heat of the race, in a tight transition, it is handy to be able to very quickly drop a gear and rev match precisely to not upset the car. Also, the performance gain is pretty substantial. After driving the race car, a 1st gen with header and carb setup and the light flywheel, a stock 1st gen feels like you are towing a boat around behind you.

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Old 10-25-03, 12:31 AM
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Lighter flywheel and new clutch are both on the list. I'll likely go with aroun 9-11 lb flywheel. I can't even imagine driving a 3 lb. Nuts.

As for wheels, I'm now looking at a 13x8(I'd like to go with a 14x8, but Hoosier doesn't seem to sell a 14 inch slick). I'm definitely going to go with the Diamonds as they are quite cheap, light and I like wheels that look purposeful . As far as offset goes, should I stick around +40 or go with more/less? Along with this, what would be a good tire size (both width and height, mainly height is what I'm wondering) to run? Any tire suggestions other than Hoosier?

Near as I can tell, somewhere around 7-8 inches wide and 18-19 inches tall seems reasonable, but those are both based on very little fact and more "sounds about right".

Thanks to anyone who can help.

Last edited by Redwood; 10-25-03 at 12:45 AM.
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Old 10-25-03, 03:25 AM
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How do you expect to fit 13x8 wheels over your TII Brakes?
I run 15*7.5 rims with 225/40/15 Victorracers. I find that a NA lacks alot of low end torque so don't go overboard in exhaust piping sizing.
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Old 10-25-03, 10:32 AM
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an 88 GTU in CSP??? are you sure, your thinking the right class. I am pretty sure that the FB's and Sa's are the only rotarys in CSP.
I guess I will check my rule book.
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Old 10-25-03, 12:19 PM
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CSP for all NA FC, TII are in BSP, I believe.

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Old 10-25-03, 12:26 PM
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Originally posted by Wormiez
How do you expect to fit 13x8 wheels over your TII Brakes?
I run 15*7.5 rims with 225/40/15 Victorracers. I find that a NA lacks alot of low end torque so don't go overboard in exhaust piping sizing.
An excellent point that I had yet to consider . Looks like I'll be going with a 15 inch rim then. That's why it pays to ask questions on here first I suppose. Thanks for the heads up and example.
As for exhaust, there is already a system on the car. I've driven a stock and large diameter (in terms of exhaust) 2nd gen before, and this car's system seems to be a great compromise. It's without a doubt the torqueist system I've felt.

Originally posted by 851stgen12a
an 88 GTU in CSP??? are you sure, your thinking the right class. I am pretty sure that the FB's and Sa's are the only rotarys in CSP.
I guess I will check my rule book.
1st and 2nd gens in CSP. Likely to be your competition at a few events if I head down south for any.
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Old 10-25-03, 12:58 PM
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Originally posted by Redwood
As for wheels, I'm now looking at a 13x8(I'd like to go with a 14x8, but Hoosier doesn't seem to sell a 14 inch slick).
You can't run "slicks" in CSP, just the tires will bump you to a prepared class per SCCA rules.

My suggestion is to drive the car as is for at least one season then decide on what to modify.

BTW: Do NOT buy coilovers with out upgrading your AGX shocks too. I spent 2 seasons on GC Coilovers with AGX shocks. They do NOT like the high spring rates.
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Old 10-25-03, 06:05 PM
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Originally posted by CarmonColvin
You can't run "slicks" in CSP, just the tires will bump you to a prepared class per SCCA rules.

My suggestion is to drive the car as is for at least one season then decide on what to modify.

BTW: Do NOT buy coilovers with out upgrading your AGX shocks too. I spent 2 seasons on GC Coilovers with AGX shocks. They do NOT like the high spring rates.
Oh, I hadn't read the tires area yet, glad I didn't purchase anything. As far as running for a season goes, that is definitely a possibility. I will be doing the last couple events out here so I can feel the car a little better before I do anything, but I don't think I'll leave it completely as is. At a minimum I'll be switching the tires and adding a better clutch/pressure plate/flywheel combo. For the rest of it, it will matter how the car feels to me over the next couple weeks. Oh, and I would also purchase new shocks with the coilovers too as I've heard only bad regarding the GC's and AGX's.

Thanks.
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Old 10-26-03, 01:28 AM
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The list can get pretty extensive ... for any SP car. But for CSP, weight is your enemy. Anything you can do to reduce weight, do it. But first ... your suspension and drivetrain need attention.

1) Coilovers are a must.
2) Bigger front bar.
3) Torsen differential (if the GTU doesn't already have one).
4) LIGHTweight flywheel and clutch. 3lbs might be a bit extreme, but a 8.5lb flywheel should still be easy to drive.
5) Poly bushings ... offset if you can, to gain you a little more camber.
6) Lightweight wheels and RACE RUBBER. I cannot believe that you're regional competitive on street tires.
7) The smallest, lightest seats you can fit into.

BTW, I think your TII brakes are illegal. Only brake rotors are free in SP. Probably not something you need to worry about right away. But, if you start going to National Tours, ProSolos, and/or Nationals, you stand a chance of being protested and DQ'd.

If money is an issue, I would get the wheels and race rubber first; with coilovers coming shortly thereafter. Your learning curve grows exponentially on R-compounds. And you'll see the need for stiffer spring rates as the increased grip will exaggerate the yaw and body roll of your car. Hope this helps.
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Old 10-26-03, 04:55 AM
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TII brakres are allowed its goes with the back updates rule. Because the GXL and the GTUS had the TII brake calipers, so you are allowed to run them. Unless SCCA ruling is differnent then my CACC rule book on this rule.
In this years canadian CACC Slalomn championship a first gen took first place.
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Old 10-28-03, 01:05 AM
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Ahh ... I did not know that. So, nevermind ... the TII brakes are kosher.
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Old 10-29-03, 07:06 PM
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I would love to have some more rotary compatition!!! Fc or Fb. Head on down... not sure when the first race of the season is though.
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Old 10-30-03, 07:51 AM
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I hope this isn't your daily driver. To have a competitive SP car it will not be streetable.
The spring and damping rates you will need are going to be pretty high. I like the entire GC setup for the FC: springs, DA shocks, and camber plates. You can call GC and they can make suggestions on a good starting point for spring rates. Then get a set of adjustable street sway bars.
I haven't read the rules lately but I don't think a torsen will be legal, since it was never offered in an FC.
Weight: Like someone else said take everything out that you can. You can remove the entire A/C system, and the stereo. There is also some wording about removing unused wires... and there is a lot of wiring in an FC. This will come in handy if you go to a stand alone ECU. Which will be necessary to make the max power... An IDA setup would be pretty nice, since the intake is open for mods. The seats are also very heavy. You can get a 16lb Corbeau Forza for a little over $200. Use a shifter cart seat for the passenger side. I know a gy that runs a shifter cart seat in the drivers side too. I think they weigh less than 5lbs.
Wheels. I would pick your offset based on keeping the rims as far under the fender as possible. A narrower car doesn't have to drive as far to get around the cones. So put the inside edge of the rim/tire as close to the strut as you can. You should have lots of wheel and tire options in a 15".
Find a local plastics supplier and buy some Delrin AF. If you have FSAE experience then you should be able to make your own suspension bushings on a lathe in no time. The raw material will probably cost less than $50.
Good luck

Last edited by Travis R; 10-30-03 at 07:56 AM.
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Old 10-30-03, 02:02 PM
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i won the houston csp title in 2001 with my 91 na, the biggist change i made was 3rd gen wheels[16x8] with hoosiers[245x16&265x16] ground controll coil over, advance design shocks, all set up by ground controll. very helpful people there. Also the Mazda trix dual exhaust. 4.33 gear kass dif. a 8lb flywheel. new tires ever 5th autox makes a big diff. that's what worked for me. oh yea the ride on the street sucks. now a trailer car
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Old 10-31-03, 02:40 AM
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All great suggestions, however I do need to keep this car somewhat streetable. My previous ride was a gutted (weighing in wet, with driver at 2100 lbs) 1st gen that I used as a DD also. It was not pleasant. The ride was fine (Tokico shocks, ST springs, poly bushings) but the creature comforts were a bit too spaced out for me (no heater, radio, wipers, headlight motors, etc.). This car will be a race car that I use on the street. Therefore I need to make compromises.

As much as I'd love to make a trailer car, it isn't too practical for me right now. I'll likely go with a GC setup as I have heard only good things. As for bushings, I'll be getting poly for now and I think I'm going to pick up some delrin to start trying to make my own. Sways, I'll upgrade there. Clutch, probably not a very streetable one, but not the most extreme either, still looking. Flywheel, likely to be 9 lbs. Exhaust, set for now. Rear gears, set for now but will keep my eyes open for a good deal. Tires/Wheels, thinking about running a season on stock rims and V700s or Hoosiers, then evaluating. Interior, I'll be removing the sound deadening here soon and the seats will be switched to something lighter (probably a forza and a shifter cart seat, good suggestion). A/C will come out all the way soon. I'm looking for a manual steering rack.

I want to be competitive in my region, not on a national level at this point. Having seen most of the CSP cars around, I think going to extremes may not be necessary. Throughout the course of next season I'll be able to see how I'm doing and where I could improve. It's been a long time since I've driven an RX-7 that was this close to luxurious, I like this feeling

PS - wannaBep - New tires every fifth auto-x? Wow. I'm a college student too, it makes it tough
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Old 10-31-03, 09:15 AM
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Your right, $$$ but you won't believe how much they go away. the hoosiers dont last long. i even clean them and treat them ever weekend. i wanted to beat them damn Miata's they told i wouldnt be able to with my RX7
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Old 10-31-03, 09:40 AM
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Originally posted by Redwood
I want to be competitive in my region, not on a national level at this point. Having seen most of the CSP cars around, I think going to extremes may not be necessary.
You ever been to a Divisional or Tour in your region? Here in Texas CSP has some well put together cars. To be competitive (trophy) you won't want to drive it on the street.

If you want to be competitive and streetable CSP is not the place to be; ES is.
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Old 10-31-03, 04:05 PM
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Originally posted by DamonB
You ever been to a Divisional or Tour in your region? Here in Texas CSP has some well put together cars. To be competitive (trophy) you won't want to drive it on the street.

If you want to be competitive and streetable CSP is not the place to be; ES is.
I have not been to the large events since getting serious about the sport. I'm sure that I will not be able to compete at these but I should be able to manage (talking snag a podium or two, nothing too special) at the local events. Like I said, it isn't practical for me to make the switch to a trailer car and the car would require a bit of work to get back to ES spec, something I'm not really willing to do either way. I figure I'll do some mods and learn the car well enough that, when it comes time, I will be able to be competitve running with the big boys.
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Old 10-31-03, 04:12 PM
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Hey redwood, the best advice one of the long time RX7 driver, was go to 16inch tires, better choices. and run the biggest tire you can. that was from dave at Mazdatrix
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