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Scca STX autocross build

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Greatly appreciate the content and quality of these posts!
I'll second that. Just participated in my first autox last weekend running in HS and took first in our street 2 novice class. I decided right away that I'd like to try STX next season so this thread is perfect.

I'm still unsure about a few mods so maybe someone can clarify for me. Is a CAI legal in STX? Someone in this thread mentioned it was. I took mine off to do HS and kinda miss the turbo sounds. Would it be legal to fill the stock motor mounts with Urethane?

I recently picked up a Pierce Motorworks track suspension pack which is their strut tower brace, 4 point lower brace, and torsion bar. Not sure which, if any of those would be legal or even helpful. I've heard people saying you can pick one but they may have been talking about sway bars...

Those are the bits I'm unsure of right now. I'll probably go a little crazy this winter and add an LSD and MeisterR's and a few other things I'm sure.
 


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I'll second that. Just participated in my first autox last weekend running in HS and took first in our street 2 novice class. I decided right away that I'd like to try STX next season so this thread is perfect.

I'm still unsure about a few mods so maybe someone can clarify for me. Is a CAI legal in STX? Someone in this thread mentioned it was. I took mine off to do HS and kinda miss the turbo sounds. Would it be legal to fill the stock motor mounts with Urethane?

I recently picked up a Pierce Motorworks track suspension pack which is their strut tower brace, 4 point lower brace, and torsion bar. Not sure which, if any of those would be legal or even helpful. I've heard people saying you can pick one but they may have been talking about sway bars...

Those are the bits I'm unsure of right now. I'll probably go a little crazy this winter and add an LSD and MeisterR's and a few other things I'm sure.
http://cdn.growassets.net/user_file...street_touring_category_online.pdf?1432652724

This is where you can read up on all the allowed modifications.

But, cliff's notes:

Intake, Header, High-flow cat, Exhaust, Tune(but no addition of boost), Engine Pulleys, Coilover shocks, Sway bars, Chassis bracing, Motor Mounts, Short shifter, Seats, Lightweight battery, LSD, BBK, Wheels and Tires (up to 265mm wide[tire], 9" wide[wheel]).

The tricks come in the combos of parts to cars. The OP has a great start to his build documented here. Others may go in a slightly different direction. It's cool seeing all the nuances in the paddock at nats for similar cars.
 


OP
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Thread Starter #103
The way I read the rules, the 4 point bar may not be legal because the rear attachment point is more than 2" from a suspension attachment point. That feels like a technicality, and for local competition I don't believe it matters at all. For national competition, it could be protested.

Also, stiffer bushings and motor mounts are ok, so long as they don't have more metal than oem.

Thanks for the praise too. I hope this is helpful to somebody. If anybody questions my execution or results, I'd be happy to explain my thinking. If someone has better ideas, I'd love feedback.
 


RAAMaudio

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Great thread, I like your work on the car and results obtained:)

I have modded cars for decades and have one of the most modded ST's there is but do not have any chassis braces except a two point up front as did not see a benefit to them due to how the car is designed. My car was on a lift at a major race shop and the manager took a good look at all my mods, after he had driven the car, loved the car, the mods, etc and we talked specifically about braces and he agreed with my opinion and execution.

My 2 cents on chassis bracing on this car, I could be wrong and it now seems I will be keeping the car so will explore this a bit more but likely stay with what I have done.

My two point is a 1" sq fairly thin wall steel tube cut at 45 degrees on the ends to allow bolting through it to the subframe.
Subframe was drilled and nutzerts installed to bolt it to.
Cost, scrape metal and parts on hand, barely any.
Time to build, less than 30 minutes.
Time and cost to replace if bent, I was on the road so had to buy the metal, scrap yard, new material, $2.
Damage to chassis from hitting the brace on something on the road, barely bent mounting points.

I am a staunch believer in removing every bit of weight I can reasonably do and only adding weight where I am positive it will be a benefit to overall performance of the car.
Since I do not autocross much any longer there may be some things that work for that use I would not need for mine, built for HPDE and TT events.
I have used plenty of braces and built caged cars up to one with a huge number of tubes, all I needed were new bottom tubes and could not even have a body.

My personal opinion is many parts are sold for this car that make money for the manf but not really needed and those parts make the car slower, the money could be more wisely spent to make it faster instead or get more seat time which we all need:)

Most sincerely,
Rick
 


M-Sport fan

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^^^Rick;

What would be the negatives/drawbacks for NOT even doing the DYI 2 point brace you describe above??
Does it only come into play on super high G turns/sweepers on road courses using gumball, <100 tread wear tires, and much less so on 200-300 tread wear 'street' rubber?? [dunno]

While I do NOT want to 'dis' any of the many great sponsors/manufacturers/distributors on this site, I DO agree with you on the lack of a NEED for all of this weight adding bracing everyone seems so adamant about really helping (placebo effect???).

Unless they do some kind of engineering based structural analysis, backed up by actual strain gauge empirical evidence results, it is nothing more than the proverbial "butt dyno" type of 'improvement'. [wink]
 


RAAMaudio

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Double posted again, not sure why it is doing that but my mouse is acting all sorts of weird today so might be it.
 


RAAMaudio

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I have always ran the brace since 293 miles on the car and only 5 by me when stock and easy driving so I cannot say for sure what the gain is but it does look like a good place to put one from prior experience and knowing I was going to push the car hard on relatively wide race tires.

That and the input from the race shop manager, a big shop and very familiar with these cars.

Also I needed a rear mount for the full length undertray and it was used as a rear mounted version of the front chin spoiler to help pull more air out of the engine bay, all of which the race shop manager approved of and even recommended I make it wider and deeper. The weight is around 2 lbs or less and being straight it is stiffer than something with bends in it that will have some flex. .



-------------

Placebo effect, have fallen prey to that as well but mostly in my younger days, mostly though saw others doing and when I could not afford all the toys they bought I still beat them all the time. I am sure one can feel the effect of some of this stuff but as you say, without real proof it does not mean it makes the car faster or better in anyway, different is not a good way to judge the results.

I set out to prove my understanding, from ready all the great suspension setup books available, how much the effects of overly lowering a car can hurt the handling. I drew out the suspension geometry in full scale on the shop wall so I could really get a good idea of what was really going on. To keep this short, lowering to where the ball joint pivot point was just below the level of the inner pivot point on the control arm versus 1/4" lower where the inner point was lower just a little than the ball joint. 2 seconds difference in a 45 second autocross course which is huge and the car was far more difficult to drive fast, it was very slippery and skittish, less feedback, etc.....I had everything pre marked so it only took a few minutes to change it, I made 4 runs switching back and forth within around 20 minutes. I knew there would be a difference but it was far more than expected.

No instruments except time clock and my hundreds of autocross events over several decades in 5 or 6 western states in many different vehicles.

I really do have around $50k into this car and would run all the braces made if I believed I needed them and again, I will or may I should say do some testing over time now that I am pretty sure to keep the car.

-------------

I am really interested in the new "Miata" but would not get one for a few years when the prices of used ones goes down, I would take a good look at braces for it because a company I trust a great deal makes them for it and they have three of the cars in house and they autocross and track the cars. I would still be very slow to add them to the car, only after seeing what others are doing that use the car in competition type events, and would look into trying them out first in some sort of fashion.

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I certainly appreciate your approach to the bracing on this car. I've noticed there are a couple camps. Some people have gone all out with the bracing and swear it's an essential improvement. I've also been advised not to mess with bracing and let the thing tripod. While I don't mind changing my mind or being talked out of things, I would be curious to see the difference. If I don't consider it an improvement I won't keep it for long. This is my first sport car, definitely the first car I've raced, and I admit I'm hooked on working on it. My local track is too brutal to attend regularly so autoX is what my tinkering will be catered toward. I'd really like to manage the slip in the front. I need seat time to practice unwinding the wheel and I'm happy to install and tune if it helps.

The new Miata is sharp. One took first in pro class at my region's event last week.
 


M-Sport fan

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Rick;

As far as the 'slamming' of these (and other) cars goes, I believe that the vast majority of those who do this realize at this point that it is a personal preference, AESTHETIC ONLY 'improvement', and definitely NOT a performance/handling improvement.
At least I hope that they have enough insight to actually know that this could actually HURT their car's handling/balance BIG TIME. [wink]
 


Last edited:
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I've noticed there are a couple camps. Some people have gone all out with the bracing and swear it's an essential improvement. I've also been advised not to mess with bracing and let the thing tripod.
I would imagine that 4 wheels in a turn are better than 3, but I agree getting a front wheel drive car too stiff at either end is probably not a fun ride...
 


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Rick;

As far as the 'slamming' of these (and other) cars goes, I believe that the vast majority of those who do this realize at this point that it is a personal preference, AESTHETIC ONLY 'improvement', and definitely NOT a performance/handling improvement.
At least I hope that they have enough insight to actually know that this could actually HURT their car's handling/balance BIG TIME. [wink]
Not to mention tire rub!
 


RAAMaudio

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There has been a great deal of winning FWD cars that lifted a tire, the rear end does little on these cars, not a big deal if that is what makes it faster.

I have found the majority of those that slam their cars are pretty ignorant of the effects and most can't drive worth a crap anyway, just following some goofy fad wanting to fit into whatever crowd they are seeking instead of standing on their own, sadly so:(

BUT, there are some that know but do it anyway as they could care less about the car being used as such, it is for other reasons than driving most if not all of them do so.

My real issue is when they try to defend the handling, safety, etc....there is not defense, physics negates that entirely.

BUT again, if they correct the geometry then they are somewhere in the right realm as long as on smooth roads, etc....
 


RAAMaudio

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There has been a great deal of winning FWD cars that lifted a tire, the rear end does little on these cars, not a big deal if that is what makes it faster.

I have found the majority of those that slam their cars are pretty ignorant of the effects and most can't drive worth a crap anyway, just following some goofy fad wanting to fit into whatever crowd they are seeking instead of standing on their own, sadly so:(

BUT, there are some that know but do it anyway as they could care less about the car being used as such, it is for other reasons than driving most if not all of them do so.

My real issue is when they try to defend the handling, safety, etc....there is not defense, physics negates that entirely.

BUT again, if they correct the geometry then they are somewhere in the right realm as long as on smooth roads, etc....
 


OP
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Thread Starter #114
Sorry for the radio silence, work travels have kept me pretty occupied.

First, since he's become more active in this thread, I'd like to give a big shout-out to Rick/ RAAMaudio. I mentioned in passing earlier in the thread, but Rick was kind enough to donate the strut bodies that I used to build my front Koni housings. I want to say here that his generosity and feedback is greatly appreciated and I'm glad he's part of our community. Thanks Rick!

With regards to chassis bracing, I believe that it can provide a benefit. Stay tuned, that will be in a future update.

About the FiST lifting a wheel, it sure does and that's ok. It's true that a wheel in the air isn't providing any lateral grip or braking capacity. It doesn't matter if you have less than the maximum, so long as you have enough, and even lifting a wheel the rear of the FiST has enough.

I mentioned in my previous post that riding in a student Gti was enlightening. I don't know if the changes I've made with shocks and springs have eliminated the tripodding, but I have given up some rotation for sure. If getting a wheel in the air returns that, then that is fine. The search for ultimate grip needs to be secondary to finding good rotational balance. That is what leads to a great handling car.

Sent from my XT1650 using Tapatalk
 


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Rick;

As far as the 'slamming' of these (and other) cars goes, I believe that the vast majority of those who do this realize at this point that it is a personal preference, AESTHETIC ONLY 'improvement', and definitely NOT a performance/handling improvement.
At least I hope that they have enough insight to actually know that this could actually HURT their car's handling/balance BIG TIME. [wink]
Sadly, many who "stance" or "slam" their cars don't really know that they're actually hurting the handling of their cars. Many install coilovers and just crank them down to the bottom or even remove collars to get it lower never bothering to think that they're out of the operating range of said damper.

I could go on and on but I'm lazy and at work. [shhh]
 


RAAMaudio

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I have talked to and coached hundreds on making cars handle better and by far most have no clue at all, do not even understand the simplest of terms used to explain it or just do not care. Why do I make such a big deal about this when it is their personal opinion, their car, their money, their safety?

It is because they are putting themselves, passengers, other motorists and sometimes pedestrians at risk, hundreds of crashes, lives lost, insurance rates go up for the rest of us, families suffer, more stringent laws passed that effect us all.

Of course they are not the only ones causing the mayhem but a very significant part of the problem and cause a great deal of negative public opinion against the rest of us.

Luckily I have had the fun of educating some with just a demo ride and I never go all out when doing so, no need to as it will still blown them away at what a well setup car can do and they become a believer.

I spent far more time on coaching on driving responsibly, take it to the track or at least back roads away from the public and without passengers but if you do have a passenger keep it down a notch so you have an out no matter what happens.

----------

I have recommended and promoted that all drivers must have real drivers education including activities such as autocross, I made my children do so which means they are far more prepared to handle any emergency that arises than the average person behind the wheel that panics instead of reacts appropriately when under duress.

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I have built several very fast FWD autocross and track cars, all lifted a tire, only real issue was flat spotted tires at times on a road course.
 


OP
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Thread Starter #118
How do you like the rival s 1.5?
So far so good. It has been cool enough during my first two events that I didn't get any heat in the tires, even with 70 second courses. I only got 2-3 psi increase over my runs, so I can't comment on how they drive when hot (or overheated) but they don't have any bad habits yet.

This is purely speculation, but the lsd may have a meaningful effect on how this car overheats the tires. The reduced wheelspin is obvious. The ediff overworking the brakes, and then passing that heat onto the wheel and tires will be reduced. Whether that effect passed 4? or 40? to the tires, I can't say. I can say that in HS trim managing tire temperature was a must, even in cool weather.

I hated how the original Rivals drove, even though they were fast. They were mushy with garbage steering feedback. The 1.5s have good steering response, decent slip angle and make noise when you get past their limit. I can't say these are 3% faster or slower than the Bridgestones, but they are certainly on their level.

Around town they are fine in the wet and noisey enough that I'm glad I have other tires for daily driving.

Sent from my XT1650 using Tapatalk
 


RAAMaudio

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Great review for the current issues, weather being cool, etc.....:)

I find the S to be quite good for my use but again 225's on 9" wide wheel have a decent stretch so I have good feedback, control, etc but not as crisp as some setups I have ran but for street, canyons, even a road course they would be fine but might be still a bit soft in the sidewall for autocross. They have great grip but I have over driven them a bit and found them easy to control at a pretty high slip angle but they made no noise to help know what they were doing, no warning and it is the rear of the car that comes around, front stays planted.

Setup I run, no braces, stock front bar with urethane bushings, Steeda adjustable links, 8/7k Swift linear rate springs on BC coilovers, -2.5 front and -1.9 rear camber, this worked very very well on track even with the 6/5k front linear, rear progressive springs, have not tried the new springs on track but it needed stiffer ones and better on the street as well, rides better with the upgraded springs, just have to adjust the dampers.

Adding more camber helped maintain the stock slower speed oversteer when adding more front camber, I could add a bit more up front for the track but with a big turbo I wanted the tread on the ground better for acceleration and deep braking zones.

In STX could you add more camber to the rear using a shim kit, etc?
 


OP
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Thread Starter #120
Rick, it is my understanding that shimming the rear causes errors from the rear ABS sensors. If that is not the case, then there may be some work to do back there. Have you tried it?

Also, why did you choose the adjustable end links? I haven't been able to find the purpose aside from adding preload for circle tracks. But they seem popular so I assume there is something else I don't know about.

Lastly, I meant to say this in my previous post about the tire heat. The reason I think it may be significant is that previously the wheels, especially the front were getting extremely hot. When spraying the tires, water drops were sizzling off the wheel on contact, so well over 200?, 250?+ probably isn't unreasonable. This is after a few 65-70 second autocross runs. I can only imagine how the constant duty cycle of a track day would test the system.
 




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