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Old 10-03-2009, 10:08 PM   #1
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Default open thread for the serious autox crew

Background: after 20 years of occasional autocrossing, I am going to be taking it more seriously next year; attending divisionals, a national tour, all regional events, an evo school or two and maybe a pro solo. Then maybe lurk at nationals in a year or two when my kids can travel better. I wanted to create a thread for guys serious about running the two classes that welcome turbo miatas, XP and SSM. I am hooked after getting an ftd at a corvette club event, then my co-driver getting 2nd fastest time of day at our regional a week later (I was .8 back), all while street driving my NT01s, which are not even the preferred autocross tire. Next year I want to be a threat for ftd at every regional event.

I want guys that run at the pointy end through the cones to weigh in on their setups. I know that Chris Swearingen sometime posts on here, he has what is demonstrably the fastest SSM miata in the country. I am sure there are other guys lurking here with fast autocross cars.

Stuff that is on my mind for next year is: 1. what's the biggest autox rubber I can fit under a rolled fender, are the 275-15 going to work, or should I stick with the 255-13 and adjust final drive to suit. 2. rules stuff, for example, I don't think I can run my frame rails, have guys run door bars instead with good results? 3. I want to run an aggressive map for autocross with race gas. Are guys running dual maps for two fuel types, pumping out their street gas on site, and filling up with race gas? I will be running a built probably 1.6, should I run water as a power adder, instead? 4. I am still going to street and track drive this car, anyone else doing so? 5. Diffs, I will probably go with a torsen 4.1, anyone switch from the torsen to the OS Giken, should I skip the middle step? I'm not really looking for answers to all of this, I will be trying and testing, but I want a discussion in this forum.

Discuss openly. This thread is about raping Elises, Z06s, S2000s, Evos, STIs, M3s, 911s......
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Old 10-04-2009, 12:34 AM   #2
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I can only comment on two things.

Emilio said that you can run his 15x9 6UL with 275/35/15 rubber with a fender pull and roll, remove some liners and likely a 1/8" spacer to clear the control arm. And, I think 2.75 springs will rub. 2.5" are OK.

Frame rails are technically off limits in SSM. I ran mine, but I'm generally battling to stay out of DFL in SSM so nobody cares. I just run my RS3's so my lack of tire (and lack of skill) negates my slim chance at a trophy.
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Old 10-06-2009, 08:44 AM   #3
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Well, I don't know how i'd do nationally, but i've been swapping first place finishes in my region (Atlanta = 200+ cars per event, usually about 10 in SSM) with a very well prepped C4 'Vette. Our cars are complete opposites too..mine is a daily driver, puts down ~260rwhp, running on 215-40/17 Kumho V710 this is my first year of autoX and I arrive at an event I just throw my slicks on and go..never check tire pressure, never cool down tires, run a pretty simple alignment. My comp. is running a trailered-in C4 'Vette on 315-35/17 Hoosier A6s, been autoX'ing for 20 years, makes constant tweaks to his car between runs and makes ~380rwhp.

The Hoosier A6 in 275/15 are the tire to go with. If I could run them..err afford them, I would. You are correct about the frame rails. You might get away with leaving them on for regional events if you're not killing everyone else/ giving them a reason to have officials poke around your car. If you are beating the snot out of everyone, better be playing by the book. I don't think the rollbar is allowed to have any extentions that "add chassis ridgidity". They understand that a lot of Miatas are DD cars and do allow a standard rollbar, but the front-runners only see that as extra weight and mostly don't use them. I'm running a Boss Frog Double Maxx, which has more attachment points over a Hard Dog...no problems here, but I really haven't checked the rules word for word...yet. As for maps and power...it's only as good as your tires will allow. Recently, I found out that i'm pushing the limits of my stock Torsen. Under hard cornering and acceleration, I can spin the inside wheel and not because it's lifting..it's because I have soo much grip from the V710s. In my case, more power is NOT the answer..a better diff or maybe some aero (which I plan on getting a "custom" APR GT-II aluminum wing ASAP). The 275s will only make this problem worse. OSGiken and Quaife offer nice aftermarket diffs., though finding a GURU would be awesome.

If you're looking to build a front-running SSM car for your local/regional events and have a fun DD, it's not too hard...but to be remotely competitive on a national level, you're going to need a hard-core not-very-friendly-for-daily-use machine...unless you plan on going to those events for fun. There are a few FD RX-7s that run ProSOLO/Nat's that are God-like in their speed and building a Miata to run with them will be quite difficult..but not impossible.
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Old 10-06-2009, 10:41 AM   #4
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Great info, Doppel and Stein! I'm not thinking I am going to be nationally competitive, but again, I want to threaten ftd at regional events. We have a small region with, at this point, no other ssm cars. Unless a guy with a cmod car shows up, the fastest cars are an sm evo and sti, a csp crx, a fp stang and a ep integra. On our fairly short courses, 30-40 seconds, all these cars, including me, are within 1-1.5 seconds, with me being on the slower end.

I think with a little driver training, a little more driver training, those meaty 275-15 A6s, a torsen and some suspension work, I should be where I want to be. Anyone here actually running the 275s? I'd love to get away with them with just a pull and roll. I have a call in to Emilio to see if it's possible, and I know he has a pic on his site of an NA with them on it with a pull and roll, but it looks really iffy on the back. I'm thinking of flaring, but to make it look ok with my street wheels and tires, I think I'll need some spacers. At the end of the day, I'm just scared to cut my car up like that!
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Old 10-06-2009, 11:02 AM   #5
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Welcome and I hope to see you at some events. I run a good number of east coast National events and Pro Solos and always go to Nationals. Definately take an EVO school! It will take you to the next level if you have hit a ceiling, and I just might end up being your instructor depending on where you take it. I have spent the last 7 years in a CS/ES Miata and last year ran Pro Solos in a friend's SSM 3rd gen RX7. I will be in the RX7 for Pro Solos, Tours and Nationals this year. I own a turbo Miata, but have a hard time believing they can keep up with the FDs, but I'd love to be proven wrong. The car I will be driving all next year just happens to be the 2009 SSM championship car.

As for your questions, for the fastest setup run 275 on 10" wheels which will require cutting the fenders. I'd build a 1.8 rather than bother with the 1.6. It has more power and you will probably never be able to get to the minimum weight anyways. On the diff, skip the Torsen. They are no better than an open diff if you have enough grip to unload a rear tire, which you should. The OS Giken is the way to go and I think the 4.10 ratio is probably best.

Brian Johns
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Old 10-06-2009, 11:35 AM   #6
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Damn Brian, thanks. I noticed Evo just posted the early 2010 schedule, I will probably sign up for the school in May at Devins, Mass, then run the northeast tour, whether it ends up at Devins or Seneca (I'm hoping for Seneca, because the family likes to vacation out there, anyway). It's early to start talking about 2010 without the full sched being out, but keep me posted as to where you will be, maybe you can sit with me at Evo if you are going to Devins. Oh, and on my list of fast local cars, I skipped a certain DSP E30 that you may know of from National podium fame. A.S. doesn't show up to many of our regional events, though, maybe the surfaces are too bumpy for a real national level car?

Anyway, thanks for the tech tips. These are things that deep down I know, but am avoiding ($$$$$$$$). In the end, it's probably cheaper to do it right the first time, right? When I am still roasting the unloaded tire with the torsen at a tour event, I will be sorry I didn't spend the extra (only) $6-800 for the Giken. When I am going really fast with my 1.6, I will be sorry I didn't spend the extra (only) $1k on a built 1.8.......
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Old 10-06-2009, 11:51 AM   #7
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The OSG diff. runs about $1400 for just the part..then comes install and while you're in there, might as well put fresh bearings in there. In the end, you're looking upwords of $1800-$2000 for everything..and that's with having a 1.8 7" rearend to start with. If you're looking to have "fun" and but mostly to have an even more fun DD car, a Torsen won't kill you and if you decide to do any open track days/ PDX, the Torsen will be right at home.

As for the 1.6, You should be able to make more than 209rwhp on a 2560R

Once again, everything goes out the window if you're seriously wanting to be serious.
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Old 10-06-2009, 12:08 PM   #8
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Quote:
Originally Posted by Doppelgänger View Post
As for the 1.6, You should be able to make more than 209rwhp on a 2560R
++1 on price creep. I do want to have fun, but I want to be fast at the same time. I had some fun in my HS corolla, and street prepared rabbits, but being at the fast end of the sheets is addictive! I feel like Bob on enzyte, I have a spring in my step, and I am more cooler!

That 209 was at 12psi, hot day, operator stopped at 6800. Figure that's good? I'm thinking of posting my plots and maps, and have everyone pick them apart. Maybe I'll do that tomorrow. In fairness, I asked for a conservative tune, because I just want it to hold together while I flog hell out of it at track days, and that's pretty much what I got. But, I want to be able to turn it up for autocross. As it is, I'm running right off the 'gate spring for track days, then adjusting with the mbc for autocross at around 14 psi.
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Old 10-06-2009, 02:52 PM   #9
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Webby is your motor stock?

I auto-X in STS with a 88 MR2 so I don't know if I would be a good source of info on car setup for SSM or XP.
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Old 10-06-2009, 03:06 PM   #10
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Originally Posted by MicaCeli View Post
Webby is your motor stock?

I auto-X in STS with a 88 MR2 so I don't know if I would be a good source of info on car setup for SSM or XP.
Stock motor with what the p.o. tells me was around 100k. He rebearinged the crank, and resealed/regasketed, but no rod, piston, or cylinder work. Head is untouched.
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Old 10-06-2009, 03:49 PM   #11
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Originally Posted by webby459 View Post
...Then maybe lurk at nationals in a year or two when my kids can travel better. I wanted to create a thread for guys serious about running the two classes that welcome turbo miatas, XP and SSM.
XP and SSM are really worlds apart when it comes to allowances. For the most part, all that XP requires to remain "stock" are the floors, firewall, rockers and tulip panel, and the engine block and head castings. There are some limits on minimum track and wheelbase, and some safety requirements on fuel plumbing and rollbars, but it's really an all-out fabricator's class. SSM is the class you want if you are limiting yourself to bolt-ons, not that fabrication doesn't exist in SSM.

Quote:
1. what's the biggest autox rubber I can fit under a rolled fender, are the 275-15 going to work, or should I stick with the 255-13 and adjust final drive to suit.
With turbo power, go for the 275 on a 10.5" wide wheel. You'll want the additional footprint. I'd use the 4.1:1 for a turbo car. I'm using a 4.78:1 in my NA car.

Quote:
2. rules stuff, for example, I don't think I can run my frame rails, have guys run door bars instead with good results?
I'd run every legal method of tightening up the tub that's allowed until I exceeded the minimum weight.

Quote:
5. Diffs, I will probably go with a torsen 4.1, anyone switch from the torsen to the OS Giken, should I skip the middle step?
I'd run a torsen or torsen-style diff. The OS Giken is a clutch diff. They behave very differently and affect corner entry very differently. My experience with clutch diffs in autocross is that they add lots of push on corner entry.
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Old 10-07-2009, 12:16 AM   #12
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or the most part, all that XP requires to remain "stock" are the floors, firewall, rockers and tulip panel, and the engine block and head castings.
Actually you can run any motor you want to in the chassis in XP as long as you meet the weight requirements.

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I'd run a torsen or torsen-style diff. The OS Giken is a clutch diff. They behave very differently and affect corner entry very differently. My experience with clutch diffs in autocross is that they add lots of push on corner entry.
Get a 1.5way diff. A 2way diff will tend to create a push when it locks under decel. The 1.5way allow for more slip between the tires under decel which allows for a better turn in. As SBrian2 stated, a Torsen is useless at the high grip levels of SSM.

SSM is not for the faint of wallet. I'm going against SBrian2 and attempting to build a competitive SSM Miata. Luckily I get to compete one-on-one with him and his car owner, so I'll have a good bench mark from the get go. Loosing the weight off the car is going to be difficult parts. I aim to get back to the STS trim weight of 2150 before I start going nuts to get down to the 2040 range.
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Old 10-07-2009, 09:35 AM   #13
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IIRC the minimum weight for a 1.8 turbo Miata in SSM is 2240 and 2220 for a 1.6 turbo(including the 275 tire weight exemption). Since my car is my DD and I like to have an all around nice car, I have no plans for taking off any weight...I mean, I could probably find that 200lb, but I won't ever be nationally competitive in my car so there is no point.

Weight formula is 1800 lb + 200lb per liter + 1.4L for the turbo. So that's 1800 + (1.8x 200)+(1.4 x 200) or 1800 + 360 + 280 = 2440 - 200lb per tire exemption = 2240

Over on the pointy board, FatherLeadFoot has some good posts about diffs and how they act on a tight autoX. He went from the Torsen to a RX7 clutch to a OSG. He said the RX7 diff. set with a 160lb preload caused a good bit of on-throttle push and could still spin the inside wheel under some circumstances but that the OSG unit was controllable at all times. Unfortunately, the OSG unit when all is said and done is rather expensive...but since the rules allow such parts, they're pretty much a "must have" to be competitive in SSM.

Personally, I think my car with some aero, the OSG and 275 A6s, I wouldn't be that far off , but the two biggest things to increase grip...tires and diff, are some of the most expensive parts for me to buy. I also know that with such things, i'd be whooping up on the C4 'Vette that I run against locally
But i'd be looking at $2000 for the diff, $780 for some 15x9 6ULs , $1100 for the tires $250 for the wing and $150 for a custom front splitter.
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Old 10-07-2009, 01:48 PM   #14
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Wow, good to know i'm not going to be competitive next year in SSM in my car lol. I kinda suspected this anyway.

I think I may get our Integra prepared for a stock class if I really want to compete in autox next year.
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Old 10-07-2009, 02:23 PM   #15
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I popped my 1.6's tune up in the dyno section, if someone wants to see if I can get moar powah out of my mouse motor. I am doing something fresh under the hood for next year, not sure yet what it will be.
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Old 10-07-2009, 08:50 PM   #16
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Quote:
Originally Posted by Doppelgänger View Post

Weight formula is 1600 lb + 200lb per liter + 1.4L for the turbo. So that's 1600 + (1.8x 200)+(1.4 x 200) or 1600 + 360 + 280 = 2240 - 200lb per tire exemption = 2040
Fixed that for you.

A couple of quick things
10.5" wheels are better than 10"
275s are a must
You will have to cut the fenders to get low enough
I am running a 3.90 rear end and thinking very hard about switching to 3.63

Most of my stuff is posted on my site 51 SM2

Sorry all this is short and kind of shotgunned. I am on a business trip this week and pretty tight on time.

I am glad to see more miatas expressing an interest. Obviously I have a lot of faith that the platform can be competitive in SSM.

I subscribed and will try to stay current with things but expect more detailed updates next week.
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Old 10-07-2009, 10:33 PM   #17
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Originally Posted by Midtenn View Post
SSM is not for the faint of wallet. I'm going against SBrian2 and attempting to build a competitive SSM Miata. Luckily I get to compete one-on-one with him and his car owner, so I'll have a good bench mark from the get go. Loosing the weight off the car is going to be difficult parts. I aim to get back to the STS trim weight of 2150 before I start going nuts to get down to the 2040 range.
Cool that you guys have such a deep ssm pool there in Tenn. Guys, what's the deal with the fd at nats? The one that Brian Johns is driving was not the only fast fd this year. Those were all n/a, right? I know with the right port work, the rotary can go mild to wild and everywhere in between. They also have less of an issue fitting large rubber, correct? And maybe they can be run lower than the miata? It may not be all about weight, as the fd Brian Johns will be in next year was not as light as it could be per the rules. I do know there were weather issues during the runs, though, could have effected the outcome.

Midtenn, I looked and didn't see anything on your build. Can you fill us in? FI or na? Turbo or blower? V6? 1.8? Judging from your target weight, it looks like a 1.8 turbo, but... Also, what for suspension, wheels, tires, diff?
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Old 10-07-2009, 10:44 PM   #18
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All FD RX-7s were twin turbo (at least in the US). At least one of the big dog FDs runs a 3 rotor engine.
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Old 10-07-2009, 10:56 PM   #19
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Originally Posted by wayne_curr View Post
Wow, good to know i'm not going to be competitive next year in SSM in my car lol. I kinda suspected this anyway.

I think I may get our Integra prepared for a stock class if I really want to compete in autox next year.
Your car is set up very similar to mine, except my soon to be FCM revalves and (maybe) my NT-01s.

Quote:
Originally Posted by Chris Swearingen View Post
A couple of quick things
10.5" wheels are better than 10"
275s are a must
You will have to cut the fenders to get low enough
I am running a 3.90 rear end and thinking very hard about switching to 3.63
Chris, thanks for weighing in. Don't think I haven't already checked out your build page thoroughly! The best of everything, maybe something I can shoot for in the future. Are you really running out of gear to the extent that the 3.90 isn't cutting it?

Things I know: I will run the 275 hoosier next year. I will probably run the 9" 6UL. I will attempt to roll and pull the fenders to clear, but will use flares if I have to. I am running the fcm non adj revalves with 550/350 (light comparitively, but a start). I will be getting a diff, but it will probably be 4.1 whether it's my open filled with an os giken, or a torsen. I will have a freshened engine, whether it's my 1.6 built or a 1.8 lb, built a bit less to save a bit of ching.
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Old 10-08-2009, 04:22 AM   #20
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I am running the fcm non adj revalves with 550/350 (light comparitively, but a start).
IMO that is too soft for the grip of the 275 A6. You will need much stiffer springs/shocks.
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