Ok so I my Miata is generating a lot of interest in the classifieds so I figured I would start a thread to anyone that is interested about my build ideas for my 2005 Crossfire. It is a base coupe with 6-speed transmission. I borrowed DaveOH32's race tires a couple weeks ago and am hooked on building the car for stock class autocross. To stay legal for stock class I am limited to only K&N air filters, a custom cat-back exhaust to drop weight and clear my trailer hitch for the tire trailer, along with stock size wheels with an allowance of +-0.25" offset for the wheels. So I can run a 24mm offset on the front wheels to allow slightly more tire to fit instead of the stock 30 mm. The final piece of the puzzle will be Koni adjustable shocks and the 30mm H&R front sway bar. Here is a picture of the car as it looked at the autocross with the race tires which were not on stock class legal wheels.

Crossfire_racing001-1.jpg

Here is a picture of my old autocross car that is now for sale.
6-11-06_autox.jpg

I have spoken with www.ccwheel.com about making a custom rear wheel for the Crossfire that is lightweight and still stock size. They can make a wheel that will weigh just under 20 lbs which is a substantial drop in weight from stock. The front wheels I found will drop 4 lbs from stock and cost under $200 a piece. I could have front wheels custom made as well but will start with more budget wheels till I decide if it is worth getting custom fronts done. I can't find a single stock size rear wheel that weighs less than stock so I will be going the custom route with those.

For tires I am in search of a 245/35/18 Kuhmo V710 that is ready to go in the trash just so I can test fit it. With the extra 6mm of offset I am allowed I think they might not rub the a-arm but we will see. If not I am going to be getting the Hoosier 225/40/18 for the front. In order to get the traction I want on the back, I will either be going with a 265/30/19 or a 305/30/19 Michelin Pilot Cup. By running a harder compound rear tire the natural tendency to understeer will be minimized. I am hoping the fat rear tires will give excellent traction for acceleration out of corners, which will be an advantage over the BMW 3 series which is the only other significant RWD car in the class. I believe the 305 will fit because from the dimensions I have received they are only an inch wider than the 275 Kuhmos I ran a couple weeks back and there was plenty of room to spare and the 305 will give me an extra couple of mph in 2nd gear because they are slightly taller than stock. This is important because on an autocross course a car can be made or broken since most courses stay under 60 mph and if you run out of gear too early and need a shift to 3rd you lose about 0.1 of a second for each additional shift.

That is all for now I will update more in weeks to come as I start getting parts in and prepping the car. Hopefully 2007 will be a successful year.

~Keith

 

Only thing I would keep in mind here is that the Crossfire weighs 3,000 pounds (I believe that's the curb weight for the base model) so you will be heavier than the Miata.

Good luck with your new autocross toy!

 

I'm on a mission to get a EMU / ECU shut-off for the traction control during the off season, so this should help you in 2007 if I can get something done... The darn thing kills your lap times... It might just be a thing with the manual tranny version...

 

The big thing is the Crossfire weighs several hundred pounds less than a BMW 3 Series and about 200 pounds less than a 2006 WRX. The Acura Integra weighs less but has no torque and handles amazing. I think the Integra will be the stiffest competition.

HDDP, unfortunately I don't think a EMU/ECU traction control shut off will be legal for stock class because you are tinkering with the car's computer. The traction control wasn't a huge issue the one event I ran so far and it was on a slick surface. I did feel it kick in a couple times but not too bad.

 

I keep forgetting you run Auto X... The traction control is so intrusive on a road course that I'll bet it slows me 2-3 seconds per lap by cutting the power of the engine and applying brakes when I'm powering through fast turns in a controlled drift, or trying to trail brake.

 

I agree with HDDP - that traction control can ruin play-time!!!
I've tried to drift on corners every now and again, forgetting about the traction control, and you come out looking stupid - unscathed but not sideways!!!

 

I don't have too many problems with the ESP kicking in when I've got it in the "wish it was off" mode. I can get the car sideways without too much problem. The computer doesn't limit the fun on donuts or figure eights either. There have been several instances of lonely back road tail wagging.
The computer doesn't appreciate trail braking but other than that I have few issues.
I still want to get it to a Driver's Edge event and have a little fun.

Derek, I really wish you had the chance to run an SRT to get a more educated opinion about this variant. Driving to CA for a car flog is a wee bit more than I have time for.

 

I think MMZ will have some valuable info on this, as he had the chief instructor for NASA So. Cal. drive his car at Buttonwillow Raceway and made some comments on the Traction Control issue...

MMZ chime in on this one...

 

Ok so I ran my second event in the Crossfire today but on the OEM Continental ContiSport 2 tires. The event was really fast, I smacked the rev-limiter in 3rd right before I hit the brakes in the fastest portion of the course. I was the only car in DS because the two other guys who were registered were no shows. The car handled amazingly well and I was only 2 seconds off of FTD which was a C stock 1999 Miata driven by Eric Peterson who took 8th at Nationals this year. So I am supposed to be about a second per 60 seconds slower than him with fully prepared cars based on the class index numbers. If I had race rubber and shocks I could have challenged for FTD. I have no doubt in my mind.
On another note I have done some measuring and a 245/35/18 Kuhmo will fit on the front with the allowed offset I can run. It is slightly shorter than the 245/45/17 Kuhmo I ran a couple weeks back and I can run even more spacer than we had since those wheels were a +35 with 8mm spacer and I can run a +30 with 6mm spacer. Now if my Miata would sell I could get to prepping the Crossfire for next year. I will post results when they become available.

Edit: So the results were posted. I had the 11th fastest raw time and the 6th fastest time Pax (which is an index that supposedly levels the cars out speed wise) out of 78 people. This was all done on street tires in a class where I can run on race rubber. So I have to say the car has potential.

 

Derek... it was the chief instructor driving the modded SRT? No wonder you said he had the ability to walk away from you. That's a recipe for a beating.

MMZ... what did he say?

 

feets & Derek,

My SRT6 is stock as far as mechanicals go, everything up to this point has been cosmetic.

The instructor stated that with the traction control on the car HATED (i.e. - would not allow) trail braking. With it off, he stated it was better, but still intrusive.

With it off he noted it didn't interfere 'as early' and waited until the car was really starting to break loose to begin it's job.

With that said, I have no place around here to really 'try' and break it loose. Maybe I can get some time on the skid pad next time I'm at a track and I'll turn off the traction control after making a few passes with it on and see what the difference is.

 

That's about the same experience I have had. The throttle by wire does not appreciate the brakes being applied. It'll back off the throttle despite any driver input.
As for the car, I thought you had one of the pulley/ECU cars. Oopsie.

 

Ok, I figured I would give an update, since it has been several months. The car is still stock and not going to be nationally campaigned this year mainly due to my Miata never being sold. I never got an offer from someone that was near what it is worth. The second reason is because no race tire company makes a proper autocross compound tire that is the right size for the rear. I am now thinking of campaigning some to get the car properly classed in a Street Prepared class so I can tinker with it eventually and maybe build it up to make much faster. Any thoughts about that, the car is just so much fun to drive that it kills me to just have it as a daily driver but my Miata now has 550 lb front springs and race shocks so it is a bit harsh.

 

I got the car classed with SCCA in T3 last year if you want to run that class... In my humble opinion, I would divorce SCCA and start running with NASA (National Auto Sport Association) It will open-up a whole new world to you... TT class especially...

http://www.nasaproracing.com

 

I can see what you are saying but SCCA is the sanctioning body for autocrossing. I cannot afford to get into Time Trialing or Road Racing right now even though I would like to in the future.

 

NASA has Auto X too !

 

I am aware that they do but they aren't the main host of autocrosses in the US and I know that there are no NASA autocrosses regularly held within 2 hours of me. They have then occasionally but I can go to 3 autocrosses a month that use SCCA rules.

 

Well I am now considering building my Crossfire up again. My Miata is simply not cutting it anymore, there is a frustration on setup and the car being an underdog in its current class because of it being overweight by more than 100 lbs to the earlier Miatas and CRXs. Hoosier now makes tires the right size for my car to stay in stock so I could feasibly sell my Miata and fund the Crossfire. What do you think?

 

i say build the miata and just move into a higher class. if you eventually want to get in to nasa i think its a much better platform. i'm probably going to buy an early miata for a track car next year, after i turn the crossfire in on its lease and get a new dd (still don't know, evo, gto, mustang gt, sti). what would the crossfire be competing against?

 

The crossfire is classed against BMW 3 Series (Non-M), Subaru WRX (Non-STi), and Integra Type R. If you read this forum I put a killing on the Integras and WRX that I ran against in the two events I ran. In the Miata I am running in STS2. If you are familiar with SCCA rules, I run the Miata against earlier 1.6 Miatas and Honda CRX's. In autocross weight and the ability to get a good handling car are everything. Now my current problem is the 1.8 Miata I have is about 100 lbs heavier than the 1.6 Miata and even heavier than the CRX. I am also only making about as much power as the CRX. Here is the big problem, with the 1.8 liter car I am forced to run an open rear differential (no LSD). The 1.6 Miata has a vicious limited slip available within the rules. The CRX has an open diff but the drivetrain is putting weight over the drive wheels. Basically my car is an underdog. The Crossfire is an unknown as no one has run them with race tires because the race tires just became available in the proper size. Remember this is autocross, not a track event.