Dirtbag Stock Class Autocross Car - TCCoA Forums
 
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post #1 of 6 (permalink) Old 06-18-2010, 10:33 AM Thread Starter
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Dirtbag Stock Class Autocross Car

I have a '94, I just bought the car. I'm going through the suspension to make it safe (It's got some clunks, but I'm replacing every freaking ball joint and bushing in it so that will be worked out). While I'm there, since the plan is to autocross the car in Stock Category (SCCA rulebook), I'd like to do some "optimization".

I'm concerned less about absolute adherence to the rulebook and more about plausible deniability and the ability to camouflauge anything that isn't kosher. Flat-black spraypaint, WD-40 and a gravel road work wonders for "it was like that when I bought it, I assumed it was stock" plausible deniability. Also, it doesn't seem as if the tech procedure is extremely thorough at the events I've been to, so as long as it passes a first glance I have a feeling I can get away with murder.

Since most of the cars in the "Stock" class in my club are Porsches or Miatas on A6's I don't feel just real guilty about pushing the limits on the rulebook As F Stock my direct competition would be Mustangs, most of which go straight to Street Prepared because of off-road H-pipes, but beating a Miata (or especially a Porsche) at its own game would really garner some bragging rights, so while I'm not expecting it on my first time out it's something to shoot for.

I'd really like some input from our resident ADDCO expert on swaybar choice; from what I've read it sounds as if 1-3/8" front and rear is the way to go but I'd like to make sure before I buy.

I currently have new front UCA's and LCA's as well as F&R strut rod bushings (polys for the front) and a set of KYB's and Vogtland -1.6" springs, all from SCP, in the queue to be installed.

The car has fanblades on it, which I think for autocross will be swapped out for '93+ SC wheels with 245/50 or 255/50 street tires (softest ones I've found so far that are reasonable are Dunlop SP Sport 8000's but I'm open to other ideas). For Stock class you can run A6's or for people on tight budgets there's a street tire class for street tires with a UTQG >140. I can't afford to feed it A6's so heavily sauced street tires it is.

The car has rear drums, which I'm going to swap to rear discs using boneyard parts, and then do a pad upgrade, probably Hawks. Any suggestions for other brake upgrades that could pass for stock and fit behind fanblades when I'm not autocrossing?

I also think gears would be a good idea as well as the Cobra Torsen diff. The site where we do the deed is an hour away so I think a compromise between torque multiplication and fuel economy is called for. Also would it make sense to swap for the Marauder converter, since I can't go 5-speed and pass for stock?

Also, since there are no scales in tech, I imagine making the car lighter would help out quite a bit. Aren't some of the Mark VIII pieces aluminum? Which ones interchange for some reduced unsprung weight/rotating mass/etc?

Thanks guys!
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post #2 of 6 (permalink) Old 06-18-2010, 03:46 PM
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The main problem, in my opinion, with trying to run these in stock classes is the tires. Even with the 16" wheels, there's not much for tires, and there's just too much sidewall. I don't know what the classes for you are like, but here, we've got special street tire classes for stock cars on street tires, a class for non-stock cars (with the exception of the Street Touring) on street tires, and classes for cars on race tires. If your club(s)don't do that, and all FS cars run against each other, I'd really think about going to a Street Touring class, which allows, among other things, wheels up to 18x9. And a 18 inch wheel on these works great. The usual size most of us use on these, 245/45-18, is an available size for the Bridgestone Potenza RE-01R, which was the best tire a few years back, I can't remember off the top of my head if the new version, the RE-11, comes in the same size, but the RE-01R, even though discontinued, is available on eBay, in our sizes.

I'm still running the stock sway bars, and while they could be stiffer, they work fine. The more standard ones on your '94, however, probably would need to be upgraded to be really competitive, and I think in the ST classes, both can be changed.

As for brakes, I know for the factory 96-7 Sport cars, with the 16" factory wheels and bigger brakes, there are no real good pads available. Hawk doesn't show anything available for the big brake cars except for a stock replacement type. I doubt that there's anything available for the normal brake cars either. I don't remember if you can change calipers in stock class (I wasn't stock going in, so I didn't read too much into the stock rules), but if it's allowed, swapping to the PBR twin piston caliper from the '99-+ Mustang is supposed to be a good upgrade, and that would also open up to better pads, I'm sure the HPS+ is available for those. Search the forums here for more info on that swap.

Gear changes aren't allowed until the Street Modified class per the rules, so use your own discression. Consider that the '96-7 cars could have a 3.27 rear gear, and there were trac-loks available in those too.

I imagine one could swap some of the rear suspension parts for the MkVIII parts, but I'm not sure just how much weight there is to be saved.

Kelsey S.
3 year autocrosser

"WHAT CONE?!?!

1997 T-Bird Sport, 'Interceptor' (12 ESP 2008-2012)- CAI, 2.25 duals, Flowmaster 40 series, Clear corners, BBK 70mm Throttle Body, TrickFlow upper intake, PI Intake, BBK adjustable fuel pressure regulator, LE stripes, Bullitt-style gauge faces. 18x9 wheels, Sniper tuned, 3,620 pounds


1991 Ford F250 - Air restrictor delete. Cat delete.

1991 T-Bird 'Interceptor II' (12 CP 2013-) - Race-prep, Full custom "interior", Carb'd 302, Trick Flow twisted wedge heads, stage 1 cam, Custom Koni coil-overs front, Koni yellows rear, Cobra front brakes, fuel cell, 18X9 wheels, 275/30 Hoosier A6, 4.11 T-Lok. 3000 pounds

2004 Toyota Solara SE - V6, Sport package, Muffler delete, 17X7 wheels, 235/50 Conti ExtremeContact DWS
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post #3 of 6 (permalink) Old 06-18-2010, 04:42 PM Thread Starter
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Hey, Kelsey, thanks for the input!

I plan to work my way into Street Touring eventually. I'm debating at that point whether to go the SN95/Cobra hub route or stay with the 5x108 wheels and get some bling from Custom Wheel Shop. I love the Speedstars but if I went 5x4.5 I'd probably end up with Steeda lightweights.

For now I'm probably going to swap to PBR calipers and factory rear discs, get some GOOD OE replacement (HPS+ is actually what I had in mind since the car will see fairly regular street use) pads and rotors and get some 93 SC wheels and put the stickiest 245/50R16's I can find on them. I've seen some Dunlops that are UTQG 200 and there is a Yokohama in UTQG 280 that Tire Rack says is pretty sticky, well, for what it is. Plus, since they don't walk around with sniffers or durometers, I will enlist the help of the fine folks at Pro Blend.

I'm doing swaybars regardless. I doubt they'll catch it if I can fake some patina onto the bars and the hardware, and so long as the bushings and end links aren't some crazy loud color. If they do, I'll just be in Street Touring ahead of schedule. I have yet to see our tech guy look under a car or even take a wheel off, so I'm just going to take my chances. I will have the only MN12 in the club, so it's not like they'll have a basis for comparison.

As for the gears and Torsen, I don't forsee anyone tearing into my pumpkin to look for clutches or count teeth, so any rule they can't or won't enforce is a rule I'm not too worried about adhering to. It's a lot like catalytic converters in the Midwest; if they don't have inspections or emissions testing and the cops aren't crawling under peoples' cars, who cares? I could probably step up to a 3.55 or a 3.73 and so long as the exhaust isn't overbearingly loud I don't think anyone will notice.

Our club has a seperate street tire class for Stock, and as long as you have street tires that are UTQG >140, you can play in it. Otherwise, you can run Stock on A6's or equal. I think once you move up to Street Touring all bets are off though.

I was thinking the lower control arms on the Mark 8's were aluminum and are a direct swap; I was hoping for confirmation on that. Also wondering what the weight savings would be, especially since that's unsprung weight. Also aren't the Mark 8 center sections also aluminum? May be worth building a whole new chunk with 3.73's, Torsen and Mark 8 housing.

Incidentally, the Hoosier A6 can be had in 255/50ZR16, which is about 1/2" smaller in dia than the factory tire, so if I really felt froggy I could pony up and do FS with those. They will go on a 16x7, so as long as they clear in the front that would do it, I think. As I stated before, I'm keeping the fanblades for street duty so what I put on the SC wheels would just be "race tires" whether they're race tires or not.
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post #4 of 6 (permalink) Old 06-18-2010, 07:21 PM
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I'm running the Speedstars in painted silver. I've heard that chromed wheels are weaker than painted, but I'm not so sure. I don't think there's much available in a light weight option in this pattern, but I'm not sure where bolt pattern swaps would go. I'd say stay with the standard pattern, if nothing else than there's other things that the money and effort would be better spent on.

Now consider that the UTQG number isn't a measure of grip, but a measure of wear. And while typically as the wear rating and the life goes down, the grip goes up, that's not always the case, and with Dunlop's ratings being skewed by their 140 TW tire, the Direzza Z1 Star Spec, also a very good tire. that Dunlop 200TW is probably pretty close to that Yoko 280. My experience is anything over 200-250TW is about the same grip rating. I also don't put much concern on the rest of the rating. My Potenza RE-01Rs, which are about as good as it gets, only got a B traction rating.

As for changing bars, they probably wouldn't notice (like the bars on these can be seen much anyways), but I personally like to play by the rules, (I eventually want to do a National Tour event, and they're actually through) but whatever you do is your deal.

I'm running a factory trac lok unit from a '89 MN-12. Found one at a wrecking yard from a '89 N/A 3.8 car, with a factory 8.8 and 3.27. Figure that out, lol.

The Street Touring is the only SCCA class designed to be only on 140+TW, can't run A6s or V710s or the like in that class. The PAX index for STX, where I ran last year, is better than the PAX for FS.

The general estimate I've heard when it comes to tires is the difference between average street tires and a set of R-compounds (140 TW) is about two to two and a half seconds on a 60 second course. And another 2 1/2 to 3 from R-compounds to DOT slicks.

I really recommend spending part of a season on normal street tires. Less grip is a better teacher, and it'll make you really appreciate having more grip on R-compounds. That's what I did, and it made me MUCH smoother, with less grip, especially as heavy as these are, if you're not smooth, it just won't work.

"WHAT CONE?!?!

1997 T-Bird Sport, 'Interceptor' (12 ESP 2008-2012)- CAI, 2.25 duals, Flowmaster 40 series, Clear corners, BBK 70mm Throttle Body, TrickFlow upper intake, PI Intake, BBK adjustable fuel pressure regulator, LE stripes, Bullitt-style gauge faces. 18x9 wheels, Sniper tuned, 3,620 pounds


1991 Ford F250 - Air restrictor delete. Cat delete.

1991 T-Bird 'Interceptor II' (12 CP 2013-) - Race-prep, Full custom "interior", Carb'd 302, Trick Flow twisted wedge heads, stage 1 cam, Custom Koni coil-overs front, Koni yellows rear, Cobra front brakes, fuel cell, 18X9 wheels, 275/30 Hoosier A6, 4.11 T-Lok. 3000 pounds

2004 Toyota Solara SE - V6, Sport package, Muffler delete, 17X7 wheels, 235/50 Conti ExtremeContact DWS
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post #5 of 6 (permalink) Old 06-19-2010, 10:44 AM Thread Starter
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Hey, Kelsey, thanks again for the input!

I knew that UTQG isn't necessarily a measure of grip, but rather treadwear (or perhaps softness/hardness is an oversimplification). I was not aware that UTQG's were relative between brands. Doesn't that kind of defeat the purpose of having a "UNIVERSAL Tire Quality Grade"? Also, it seems like everybody's el cheapo tires have a Traction grade of A, so it's hard to go by that. I'll probably go with the Yoko's for now and just sauce them since I'm gonna be running around on 15's on the street.

I'm actually fixing up an old Formula Vee also for Solo Vee, and if I ever did anything more than play in autocross it would be with that. I'm actually doing the Bird as a car the whole family can play with (since we all joined SCCA this year), so I'm more interested in a competent handling car that will be competitive in local events than a car I can go to National events and worry about passing tech with. I'm really curious to see what can be done with these cars to maximize their handling potential while still not climbing too high up the food chain to get creamed by a Corvette or Porsche or an Evo or some other high-end car that's better suited to autocross out of the gate.
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post #6 of 6 (permalink) Old 07-23-2010, 04:16 PM Thread Starter
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Quote:
Originally Posted by Kelsey Smith View Post
I'm running the Speedstars in painted silver. I've heard that chromed wheels are weaker than painted, but I'm not so sure. I don't think there's much available in a light weight option in this pattern, but I'm not sure where bolt pattern swaps would go. I'd say stay with the standard pattern, if nothing else than there's other things that the money and effort would be better spent on.
You can hubswap to the Mustang pattern and get Enkei RFP1's in 16's, 17's or 18's that have an agreeable (35mm on an 18x9" wheel) offset (from what I've read). FWIW.

Quote:
Originally Posted by Kelsey Smith View Post
I'm running a factory trac lok unit from a '89 MN-12. Found one at a wrecking yard from a '89 N/A 3.8 car, with a factory 8.8 and 3.27. Figure that out, lol.
What gear do you use when you make your runs, Low or Second? And I guess I should ask if you're still running the 4R70W? And since it came up I should also ask how well it takes the abuse...

Quote:
Originally Posted by Kelsey Smith View Post
The Street Touring is the only SCCA class designed to be only on 140+TW, can't run A6s or V710s or the like in that class. The PAX index for STX, where I ran last year, is better than the PAX for FS.
I looked at Street Touring but I don't think I can come up with the cheese (at least initially) to take advantage of the things they let you do, especially a big-time brake upgrade. Could you help me to understand the PAX, because I ran one auto-x in a borrowed Miata, and I had a blast, but when I looked at the results, my adjusted times and score matched my raw data almost indentically and most other people's scores were adjusted some ridiculous amount. Either they took the best fun run or I got screwed.

Quote:
Originally Posted by Kelsey Smith View Post
I really recommend spending part of a season on normal street tires. Less grip is a better teacher, and it'll make you really appreciate having more grip on R-compounds. That's what I did, and it made me MUCH smoother, with less grip, especially as heavy as these are, if you're not smooth, it just won't work.
Roger on the smooth... This will actually have been one of the lighter cars I've owned, believe it or not. Spent most of my life so far driving a pickup! And since I can't afford to run out and buy a set of A6's anytime soon, I'll be on crappy rock hard street tires for at least one season, maybe longer. Getting the car going has been a pretty rough undertaking (I bought a car that needed work).

Thanks again Kelsey!

Charlie
"We all know that small cars are good for us. But so is cod liver oil. And jogging." -Jeremy Clarkson

94 LX V8 - No longer slated for AutoX; I took the coward's way out and bought a Miata.
TODAY IN THE DIRTYBIRD SKUNKWORKS: Fixing drivability issues, rear swaybar endlinks, 2.5" duals w/ H-pipe, Flowmasters ,TCCOA spec alignment, 235/60R15s on fanblades
NEAR FUTURE: Chassis Bracing, ADDCO bars 1-3/8" F&R, hubswap, Mustang brakes, FR500's or similar BA-looking wheels.
LOOKING FOR: Mark VIII rear LCA's, differential housing and driveshaft, Marauder TC, Torsen Diff, Good Trans Guy, Good Dyno Guy
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