SCCA STX E30 Build/Introduction

[race2win]

Thanks everyone for the kind words, it is exciting to see some early success when I figured it would be mid-pack at best with the current set-up.

The transition to snap-oversteer sounds like you might be getting into the rear bumpstops - have you checked your shock travel with some kind of an indicator (zip-tie?)

Also - congrats on the strong showing! Good to see that the car can be competitive.

This is a good point, once I dis-connected the bar it may very well have compressed to the bump stops.

With the bar connected, I never experienced any snap-oversteer. It just had the typicall power-on oversteer, but it was somewhat easy to modulate, so I don't believe I was on the bump stops then. I was just hoping to tone it down a bit, but in reality power-on oversteer is a good thing to deal with, much better than understeer or inside wheelspin . It has been a long time since I have competed in a RWD car with more than 110 WHP, & even then all of those were on Hoosiers. I think oversteer is just going to be somewhat present no matter what, I will just need to alter my driving style a bit (no more STANDING on the gas mid corner like I did in the ES Miatas lol).

OP- check Vorshlag's 318is STS build (on Bf.c, maybe here). They did a serious amount of testing to figure out how to put power down effectively, it's a good guide for prepping an E30 for nationals, even if you don't do everything they did-- the suspension is the key part.

I actually followed that build closely in the day, I had a 91 318i that I was considering a ST build with. The guy that owns that car now is on this forum, & in fact has posted on this thread a couple times. The problem they were having was putting down power with an open diff...they could not run a limited slip due to the ST rules. So, where they were trying to tame inside-wheelspin, I'm trying to tame power-on oversteer, although some of the basic principles do still apply.

With only one event left this year, & big plans for suspension changes this winter, I'm not losing too much sleep on the car's handling defeciencies as it sits. Ultimately, my plan is to run no rear bar, but that will be with much stiffer springs/shocks than are on the car now.

My brotha!

STX e30s ...

Hey Doug, good to see you on here! Car looks great, feel free to chime in on my build thread as I go along. Hoping to meet you & the rest of the National STX BMW contingent next year sometime!

[Jean]

If you disconnect the rear bar, do you have another set of stiffer springs to play with?

[bmwguy325is]

You may want some adjustable end links to help with that bar.

[110stx]

My brotha!

STX e30s ...

[Bimmerman325i]

OP- check Vorshlag's 318is STS build (on Bf.c, maybe here). They did a serious amount of testing to figure out how to put power down effectively, it's a good guide for prepping an E30 for nationals, even if you don't do everything they did-- the suspension is the key part.

[fsmtnbiker]

The transition to snap-oversteer sounds like you might be getting into the rear bumpstops - have you checked your shock travel with some kind of an indicator (zip-tie?)

Also - congrats on the strong showing! Good to see that the car can be competitive.

[Nsquared97]

Very cool man! 2nd is quite impressive given the lack of developement (and lack of sleep haha) Can't wait to see how the car progresses into next season.

[race2win]

Event #2

Another update...

I didn't get much time to do anything to the car since the last event, I now have a new work schedule that has me working graveyard Wed-Sat nights, so there hasn't been much time for wrenching

I got off work Sunday Morning at 5AM, came home, packed up the car, & headed out to the Oakland Coliseum for the SFR SCCA Slush Series round #4. Even though I hadn't slept in over 24 hours, I actually felt good & very focused (must have been those extra shots in my Starbucks ;)). Here is the car on grid getting ready to go...


To recap the last event a few weeks ago, I ended up 4th out of 7 behind two top notch ST Civics & a well-prepped RX8. I was 1.4 seconds out of 1st on a 45 second course...not great considering the success I have gotten used to over the years, but considering the low level of prep my car has it was a VERY encouraging result.

This time, my goal was to back-up that performance, & to test out dis-connecting the rear sway bar to hopefully gain some off-corner power-on traction. I was originally going to completely remove the rear bar last week, but I decided I would just dis-connect one end link to test it first, just in case it had negative results. So, I made my first 2 runs with the bar still connected, then jacked up the car on grid & dis-connected the right end-link...


Wow, what a difference! However, not in a good way lol! The car went from very softly sprung in the rear to so-soft-it's-flopping-around-uncontrollably! I'm exagerating...it wasn't THAT bad, but it was a change for the worse. The car would understeer much worse on corner entry, then as I fed throttle in it would transition to snap oversteer. My times didn't fall off very much, but the car was much more difficult to drive.

The good news is my 2nd run was VERY good (before the sway bar change). This event we had 8 competitors in STX, including the same 2 drivers in the ST Civic, plus the same RX8 with 2 drivers. I ended up 2nd overall, splitting the Civic drivers & topping both RX8 drivers 8). I was 1.1 seconds out of the lead, again not great, but better than the last event, & well ahead of all the TRUE STX cars! Obviously, the car is competive in STX, & will only get faster as I develop it next year.

Back to the sway bar...obviously dis-connecting it didn't help, so I decided to re-connect it today. It was originally on the middle setting....


Since our last event is this coming Sunday, I decided to go ahead & connect it on the softest setting & try it out to see it it helps plant the rear tires.


Something to note...while working on the bar, I noticed it is VERY tight in it's bushings. Sway bars need to move & flex, so this is not a good thing. I loosened the mounting brackets just slightly, that may help as well.

The last thing I did was tighten everything up with the rear tires on ramps. It's important to tighten sway bar hardware with the car on the ground, if not it can pre-load the bar.


That's it for now, sorry for the long read, the off-season starts next week so more to come on the build in the winter months!

[Wanganstyle]

Regarding a real built LSD vs. a stock unit, having run CSP the last two years I can tell you there are a class full of 180 whp Miata National Champs that will disagree with you. There's more to a built diff than the power it can handle. Its about how it delivers the power and locks up during transitions. OS Giken has a pretty good FAQ that covers this -

No reason the stock unit cannot be built to drivers liking.

Nobody seriously competing or pushing a car on the track should be running old worn out stock LSD unit.

Tons of custom built stock LSD units with custom setting - in all bmw chassis

its much easier to custom setup a bmw Oem LSD to your liking than an OS GIKEN OR KAAZ. Sure the KAAZ comes with instructions; but the lsd unit alone costs 2x as much as a complete rebuilt/configured Oem Lsd units WITH custom gearing, already setup and ready to plug and play into the car -installed in the diff shell. Many vendors to choose from also that provide full service and custom diff building.

Cost to benefit ratio is rather important: Money does not grow on trees.

Some pro european drifting teams in the king of drift europe run custom configured stock bmw LSD.

Nobody stresses an LSD like a pro drifter. Setup is key!!!



How do I know? I set them up with my own hands often for track/autox/drift/drag.

Local sfbay cars have proven this in autox also; difference between a stock unit and a custom config stock unit is quite a bit of time. (same driver same car)

The organic discs of the Oem units allow a decent amount of feel and give compared to a KAAZ or OS carbon carbon setup.

[race2win]

Regarding a real built LSD vs. a stock unit, having run CSP the last two years I can tell you there are a class full of 180 whp Miata National Champs that will disagree with you. There's more to a built diff than the power it can handle. Its about how it delivers the power and locks up during transitions. OS Giken has a pretty good FAQ that covers this - http://www.osgiken.net/faqs.html#200903_03

Sorry, I didn't really clarify what I meant... What I meant was, in a BMW with less than 200WHP on street tires, spending big money on a custom diff wouldn't net a measuarble gain on the watch in autocross. In a sub-2000lb 180WHP Miata on 275/15 Hoosiers, different story ;) You are right however about there being more to a diff than how much power it can handle, there are definite benifits to a good diff in any situation, the question is will all that money make my car measurably faster?

One of my goals with this build is to do it cost effectively, so that others in the E30 community can duplicate it without spending what their car is worth just on a diff or custom shocks. In 2005-2006 I built one of the first Nationally competitive STS Miatas (then it was STS2) in the country. I put it together with basic off-the-shelf parts for a very reasonable budget, & was able to win a National Tour & Pro Solo against a multi-time National Champion who had just about as much money invested in their shocks & springs than I did on the entire build. It's a lofty goal to expect those kind of results with my E30 now, but that is my target anyway :D

As far as a 318is in STX, I'm just not sure. Yes, it will be the lightest and smallest car in class, which is always what you want, but the lack of torque will always be it's Achilles’ heel. A E36 328is is probably the best base car to start with but you 325is developed might have a chance. If I can give you any advice, test, test, test. Buy some cones, a cheap single beam timing system, and find a local site you can rent. Then throw out what you read on the internet and try a bunch of different springs, sway bars, and tons of wheel/tire combos. Don't be a lemming. Be a trail blazer and try new things.

Thanks for the advice! I think I am definitely attempting to be a trailblazer by building an E30 325 for STX...no lemming about that for sure. I will do some testing for sure, but I honestly feel the car will be pretty close right out of the gate...it's already proven to be within striking distance with virtually zero development. I do agree the items that will need some testing will be spring rates & possibly shock valving, & then tires (different brands & sizes). Then, just get it as light as possible

[McCall]

As long as the temps are above 70*, no question the 225 RS3's on 8s will be best. However, if it rains, or is even cold out, they do not work very well at all...they NEED heat to work best. The Toyo R1R's are best when wet and/or cold, & the Yoko's & Dunlop Star Specs are in the middle...pretty much GOOD in all conditions but not the best in any particular area. To run a 235-wide tire, you would need to run a 17...I'm just not sure it would be worth the weight penalty to run those over the 15s. However, my plan is to test some 17x8s wrapped in 235/40-17 Dunlop Star Specs...
You mention the 225 R1R's...have you tried the 195s? That particular tire has a different tread compound than other sizes, this is why all the ST Civics use them. At your car's weight, they just might work, if I had your car I would try them.

I hear what you are saying about the R1Rs, but even at colder temps, I never liked the overall grip they provided nor did I like the steering response and feel at the limit. Regarding the 195/225, I still think that was more an internet rumor encouraged by a few select Civic drivers and was nothing more than that. I read the whole thread on SCCAforums as well as talked with competitors in the grid and there are just as many who dismiss it as try and substantiate it. Anyway, for STX I agree with staying light with 15's and going 225s on 8" wide wheels. In the end, buying a couple set of wheels and tires, and then testing, testing, testing will really let you know the best set-up.

That version of Fastrack is fairly old, they ended up keeping status-quo in regards to differentials. STC, STF & STS are OEM Viscous LSDs only, the rest get any LSD unit. For you (& myself) I honestly do not see the need to go with an aftermarket diff...just bolt in a good rebuilt S4.10 diff & call it good. You would have a hard time convincing me that an OS Giken, KAAZ, etc diff would be a significant improvement on the clock over a good BMW LSD diff...especially on anything with less than 200 WHP.
Most of the proposals in regards to Street Touring are still in the BOD's hands & not 100% official yet. There is one thing for sure though, as of 1-1-2012 class-hopping will be a thing of the past in the Street Touring category. Only cars specifically listed are eligible to compete in each class...so for you, & every other E30 in existence, STX it is That being said, I still think a 91 318i/is could be a dark-horse, especially at 2300 lbs !

Yep, the diff thing was from Feb as I stated but I must have missed where they finally provided an decision. They sometimes sneak those out months later so I missed it. So while it's a bummer, I understand their reasoning about it being a bit more than a bolt-on. Heck, I'm booted to STX anyway so that's a non-issue now.

Regarding a real built LSD vs. a stock unit, having run CSP the last two years I can tell you there are a class full of 180 whp Miata National Champs that will disagree with you. There's more to a built diff than the power it can handle. Its about how it delivers the power and locks up during transitions. OS Giken has a pretty good FAQ that covers this - http://www.osgiken.net/faqs.html#200903_03

As far as a 318is in STX, I'm just not sure. Yes, it will be the lightest and smallest car in class, which is always what you want, but the lack of torque will always be it's Achilles’ heel. A E36 328is is probably the best base car to start with but you 325is developed might have a chance. If I can give you any advice, test, test, test. Buy some cones, a cheap single beam timing system, and find a local site you can rent. Then throw out what you read on the internet and try a bunch of different springs, sway bars, and tons of wheel/tire combos. Don't be a lemming. Be a trail blazer and try new things.

[Wanganstyle]

You would have a hard time convincing me that an OS Giken, KAAZ, etc diff would be a significant improvement on the clock over a good BMW LSD diff...especially on anything with less than 200 WHP.

Agreed. I'm running a KAAZ unit with a close to 200hp high comp M20, still don't have enough torque to really use the LSD to the max

a moderately or aggressively set OEM diff is usually enough for close to stock S52/S54 power for motorsports use with slicks

[325ix]

I will be looking back to this thread next summer when I prepare my car for the track and auto-x.

[Cinnabar325is]

That is exciting news about STX. Thanks for the helpful clarification too.

[Nsquared97]

That's some pretty exciting news, can't wait to see how it pans out.