Autocross EVO - Street Modified Build

[EVOlutionary]

Well, I figured since half of the country has a few months off from racing we could pass the time talking about what we could or would do to make our cars more competitive in Street Modified class of SCCA Solo2 racing.

What would you do with an unlimited budget?

What would you do if you only had an $xxxx budget?

What part or technology that is not currently used on the EVO do you think would help?

Let's hear it! I will share my thoughts in a later post. . .


EVOlutionary

[EVOlutionary]

OK, here goes. This is my thought on what it would take to win a National Championship in SM, unless you are a phenominal driver who can make due with less. Starting from the ground up:

WHEELS AND TIRES
The standard is 285/30/18 Hoosiers on an 18x9.5-10 inch rim. Wider is probably better. If you can cut the fenders and/or install a widebody and run 315 or 335 tires, I think that would be best. Of course go with the lightest, strongest wheels possible for your budget. FN01R-C's are popular because they are inexpensive and average weight. If someone can find me an 18x10 that weights 17 pounds or less, me love you long time

SUSPENSION
It's quality, not quantity. You can have a big $$ set of shocks, but if they are not optimized you will get whooped by someone with perfectly tuned JICs. Unfortunately, at the National level, there are not alot of guys who will just give you the setup they are running because they have hundreds of hours and lots of $$ of testing invested into it. All I can recommend is to become friends with someone who knows alot about suspension and work with them/learn from them. Trial and error. Run your shocks full soft. See how the car feels. Run them full hard. See how the car feels. Then work in from the extremes. Most folks run a rear sway bar, some a front sway bar. Some crazy guys run no sway bar and super stiff spring. The combinations are limitless. You want your car as low as possible to lower the CG, but you need to me mindfull of roll centers. The new Whiteline Roll Center kit is looking promising. . . My suggestion - talk with Navid, Andy, John, Mark, Eric, etc. and learn as much as you can as far as what it takes to make the EVO stick under AX conditions.

POWER
MY FAVORITE! It is my opinion that you will need between 400 and 450WHP to win Nationals in an EVO. Some guys run less, some guys run ALOT more. I, personally am in the middle of that range. Too much low end torque is not always good. If you have really hard hitting power coming out of corners you will spin tires, as the EVO is very prone to lifting wheels and getting light on the inside tires. This may be able to be resolved with suspension work, but so far I have not heard of anyone perfecting it. A 2.3L stroker with a TME turbo is probably not the best way - too much TQ and not enough top end. A 2.0L with a 20G variant, or possibly a 2.0 or 2.3 with a 50 trim I feel will be optimal. I recommend a built motor that can rev to over 8000rpms. Instead of riding the rev limiter in 2nd gear (or *gasp* shifting to 3rd) and losing time and accelleration, get a built motor and take it all the way to 9000 in 2nd gear. With the 285's that should get you to about 75mph. Alternatively, you could get a higher gear (lower numerically) so that you can go faster for the same RPM. Smooth power is key. You don't want compressor surge, BOV stuttering, or anything like that at part throttle. The throttle input should feel as though it is directly liked to boost pressure (just how a stock EVO feels).

WEIGHT SAVINGS
There really isn't a WHOLE lot you can do. Start with an RS so you have the aluminum roof and no ABS crap. Lose the back seats and rear seat belt stuff. Get light weight racing seats. Get harnesses that attach to the rear seat mounting points rather than a harness bar. Harness bars are pretty heavy, and high up in the car. Get rid of AC and stereo stuff. Light weight clutch, carbon driveshaft, brake rotors, wheels, etc. to save rotating weight. Consider the stock FMIC - those big aftermarket ones weigh a ton. Consider a small radiator - you will save weight on the radiator itself, plus water weighs like 9 pounds per gallon or something.

AERODYNAMICS
To be the fastest in a big heavy car like the EVO you need every advantage you can get. Run as big of front splitter as allowed. The rules for splitters and wings are changing for next year, so keep an eye out for what the new limits will be. Some people set up the car to be loose in slow corners to help rotation, then use a big rear wing to stabilize it in high speed corners. But, having too much rear downforce without matching traction in the front is not going to be good. Make sure your car is balanced. Once again, run as big of a front splitter as possible, and one that is properly designed. Just a flat piece of FRP or carbon bolted under your front end may give you some benefit, but is not optimal. Take a look at the Voltex big splitter on the Cyber EVO for one that looks like a well thought out design.
As a side note, I hope that the SCCA "keeps up with the times" and does not continue to shy away from aero modifications, especially in Mod and Prepared classes (including SMod). One look through the pictures from JOnDemand's trip to the Time Attacks in Japan shows just how prevelent this is in other parts of the world. I think America is playing catch-up a little bit in the tuner car aero field. . .

DRIVETRAIN
There is a lot of variation here. You may be able to get away with a VCU center diff and stock F+R LSDs. You may see some folks trying the Cusco 35/65 center diff. Right now my car is tail happy enough, don't think I want to experiment with MORE rear power! Currently I have a Quaife FLSD, stock center and rear. Even with the Quaife I still have trouble with spinning the inside front tire coming out of corners. If I had the money I would be running Cusco diffs in the front and center and a TRE prepped stock rear diff. Never really driven an ACD car, so I can't comment on that. From what I have read it will probably be better than the VCU for autocross, more tunability potential, but heavier and more complicated. Stock tranny is fine. Probably won't break one at the power we will be running. Lightweight clutch, flywheel, and driveshaft will all get you from corner to corner quicker.

Please feel free to add anything I may have overlooked. . .

EVOlutionary

[Warrtalon]

I now have the 18X9.5 wheels with 285/30s, a great suspension setup, and good brakes. My downers are little experience with less than 400whp, although over 400wtq. I am not sure how you make use of 500whp when you very rarely get to (or above) 6000rpm in 2nd gear, which is where you would start making all that peak whp, right?

[markdaddio]

With a return to nationals in street mod planned for this year, I will weigh in on this as I get furthur on in the prep update. What I ran in 2005 was basically a Street Prepared car with camshafts, and drilled brake rotors. Updates for this year are: Relocation of ball joints front and rear are being done now, along with bump steer correction. I will be running 18x10 front, and 18x9.5 rear with 285/30/18 tires. Also will be running race seats for the weight savings, but unwilling to give up the A/c for the long drive out to Topeka. As for aero, not entirely sure there, but will have a splitter and wing. I think there is a huge amount to be gained with center diff control, and plan on upgrading that also. As for power, I only make about 375 to the wheels, and am not sure if more than that is really neccessary for autocross. That will be decided after I run a few events on the new suspension and center diff setup. Oh, and Hoosier A6 for tire choice.

Mark

[Warrtalon]

Would be nice to have a strong contingent of Evos in SM this year at Nats. I'll be there hoping for a top 10 finish, but if Evolutionary was the top Evo and only finished 9th, then that may be a bit too optimistic, especially with him going again and now good ole Markdaddio going. I expect both of you in the top ten, but can anyone even touch Tunnell?

[EVOlutionary]

The 400 to 500 whp #'s were referring to #'s on an average Dynojet. Last year with my 20G9-5 I made 370 on Buschur's dyno, which I am guessing would be around 410-420 on a DJ. This year I hope to make 420 on Buschur's MD (450-460?? on a DJ)

Last year at many regional and divisional events, and even at Nationals on the West course I was riding the rev limiter at 8000rpms in 2nd gear, sometimes for a whole second or two. I know a certain national championship winning EVO that in some events would ride it for at least 3 seconds in some spots, although his rev limiter is a little bit lower than mine. I feel there is definitely time to make up there by being able to accellerate through the whole section.

I bet if you looked at logs from AX runs you would be surprised how much time you spend between 5000 and 6500 rpms. Remember, the more grip you have and the faster you become, the more time you will spend at higher speeds and higher RPMs. Then again, your region may favor tighter, slower courses. . .

EVOlutionary

[Warrtalon]

Maybe it's just my region, but I've never been that high in 2nd gear. The only time I got close was a VERY LONG straight - longest I've ever seen (not that I've been doing this for long), and instead of hitting the limiter at 8k, I shifted to 3rd at 6500 or so. I can't imagine being at 8k in rpm bouncing off the rev limiter for multiple seconds - that's an incredibly long straight it would seem.

[EVOlutionary]

At Nationals there is alot more strategy going on than I ever realized. Being so late in the fall, running 2 drivers will help keep heat in the tires. Running a higher car # so you run later in the group will give you a little advantage as the earlier cars continue to brush off the sand and lay down more rubber. Also, for some I think there is a psychological advantage of going out for you last run knowing right where you stand and what you need to beat. I was #11, so one of the first cars off. I was in 3rd after my last run of the 1st day, but then I watched as cars continued to run faster and faster on thier final runs and knock me back.

Welcome back Mark. Andy Lieber has had nothing but good things to say about you, and I look forward to racing with you and learning from you.

EVOlutionary

[SS RX7 r2]

Originally Posted by markdaddio

With a return to nationals in street mod planned for this year...
Mark

Evolutionary,
You mentioned "Remove all the undercoating/rustproof/sound deadener.", is that legal in SM? Also don't forget the diffs. Your car looked good at nats.

Rick

[EVOlutionary]

Thanks! Was that your car I saw on the cover of SportsCar? Nice!

To tell you the truth I don't know if it is legal or not. I don't specifically remember it in the rules, so I will have to go back through it. I am just talking about the black tar gunk under the car and in the wheel wells, not the Dynamat type sound deadener inside under the carpet. I could not find any allowance in the rules for removing the carpet padding or interior sound deadener.

Since the stuff under the car is basically a heavy tar-grease stuff, I think it is possible to remove some of it with "regular cleaning and maintanence" of the car. So if it happened to all get washed off when you went through the car wash, I don't see how the rules can force you to reapply it. As I said, I will have to look into the specific rulings further. Great point. Thanks!

EVOlutionary

[Bullet01]

Jarrod- I just read the SM section of the rule book and it doesn't say anything about removing or not removing underbody coatings. I would email the SEB and ask them the question just to be on the safe side. Im not saying i would protest in any way, i am just looking out for you at the national level. Your best bet is to email Marcus and ask him.

Let us know your outcome from the SEB.

Thanks
Scott

[EVOlutionary]

Hey Scott. Thanks for the info. I will contact Marcus.

[Bullet01]

Hey Jarrod, No problem.

[donour]

Originally Posted by EVOlutionary

Last year at many regional and divisional events, and even at Nationals on the West course I was riding the rev limiter at 8000rpms in 2nd gear, sometimes for a whole second or two. I know a certain national championship winning EVO that in some events would ride it for at least 3 seconds in some spots, although his rev limiter is a little bit lower than mine. I feel there is definitely time to make up there by being able to accellerate through the whole section.

This is also true of John/Andy's old ESP car which now lives down here in NM and running the stock 04 rev limit. It's owned by the Love family down in silver city. We (the Love's in BSP and me and STU) spent a pretty sad amount of time pegged on the rev limiter on 2nd. I had a distinct gearing advantage running the 245/45 rather than 245/40. I didn't think it would actually make that much difference.



d

[EVOlutionary]

Donour - I met the Love's this year when they were up for a race. It was kind of funny seeing all the old Showcase Mitsu. cars back at the same race!

I don't know if it will make a significant difference by not riding the limiter, but mathematically it will make a difference. But, add up enough of those "won't make a big difference" mods, and sooner or later you will have a significantly faster car. . .

EVOlutionary