SCCA STX E30 Build/Introduction

[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]

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!

[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.

[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.

[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.

[110stx]

My brotha!

STX e30s ...

[bmwguy325is]

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

[Jean]

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

[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!

[race2win]

Winter Update, Time For Shocks & Springs

Hey everyone, been a little while since the last update, my crazy work schedule & the holiday season have prevented any progress with the car.

So, I'm just about ready to pull the trigger on a shock/spring/coil-over set-up, so I thought I would see what the E30 community consensus was. Initially I was deciding between AST, TC Kline & a custom Koni/Ground Control set-up, & now I'm adding another possibility to the mix...a custom adjustable Bilstien/Ground Control set-up. Any real world autocross or track experience out there with any of those set-ups?

Here is what I am leaning towards...The owner of Fat Cat Motorsports, who is a Bilstien guru in the Miata community, says he should be able to build me an adjustable set of custom monotube Bilstiens. So I am thinking of going that route with a Ground Control coil over set up with custom spring rates to match my set-up. The benefits of this set-up would be dealing with semi-local companies to me that have proven competition motorsports success & great support, plus it would be a semi-low cost alternative to ASTs etc.

Assuming I go this route, what is the consensus on spring rates? My goal is to make the car transition very well, so I'm initially thinking of very stiff spring rates & no rear bar. Anyone with suggestions on spring rates? What kind of difference front to rear should be used with no rear bar?

Other than the suspension, still planning to go through the brakes, header & custom exhaust, fog light deletes, race seats, light weight battery, & then test a 17" wheel/tire package

[110stx]

I've driven an e30///M3 that was setup on GC coilovers with Koni SAs, GC camber plates, etc. It was great. Conant has since gone with AST 5200s.

But when I began setting up my car, I went with ASTs. I have AST 5100s and Vorschlag stuff.

It is great stuff.

The car was (until very recently) my daily driver too, with ASTs and 550/630 lb-in springs. No big deal there. I just stayed out of the big potholes and the car was fine.

My only complaint -- and it's really my fault for pushing the ASTs through winter weather in KC -- is that the rebound adjusters (at the bottom of the struts) seized up about midway through the 2011 season.

I don't change the adjustments much, but when I want to, I want to ...

I'll be getting the struts rebuilt for 2012 season and won't be pushing the car through the snow any more, so hopefully that won't be a problem going forward.

d.hitchcock

[Jean]

race2win - if you go that route, I would love to hear more about it.

My current bilsten sports were sent to bilstein for a re-valve job, they have been used with 550front/675rears IIRC and netted me and my co-driver 1st and 3rd place last year in SM class locally. This is with a cabrio front bar, no rear bar, dot r-tires and gc plates.

The valving is not easy for daily driving though, very rough over potholes or under hard braking if it's bumpy. I may have to re-visit this again or swap to another insert.

[Bimmerman325i]

I have AST 4100s on my Manwagon, and I would put them on an E30 in a heartbeat. Each click makes a very noticeable difference in feel to the driver, which is (imo) worth the price differential over GC or TCK. I have TCK DAs on my M3, and they are great shocks...but they require more clicks or turns (comp / rebound) to have a noticeable effect. I'm drooling over the AST 4250s that just got announced, they will be epic TT killers.

I can't speak to Bilstein-based kits, but for a competitive autocross build I would not waste my time with anything that is not adjustable, and adjustable to where you can feel the difference between a few adjustments (like GC/TCK/AST/$$$$$). If the shocks used in the Fat Cat kit are PSS9-esque, that could be good, but if they're converted Billy sports without any adjustment, I wouldn't do that unless there are other cars with the same setup you can drive to test. Probably still wouldn't, if you're doing a serious all-out build.

[e30bulldog]

race2win:

Looks like you have a good build on your hands. I am currently driving a 88 325is in STX. I am also using a GC setup with koni D/A's... and I love them. I drove my car for years in a similar for that yours is in now. I had big sways all around (25/22), the rear bar does great when you have soft sport springs under the car.

I have driven cars with the fatcat motorsports suspension (miata of coarse) and I really did like it, my only beef with it is there is no adjustment. Even a car with just single adjustables is worth it to me.

I have recently bought a set of hankook rs3's, they are phenomenal...unless its cold and then they are useless...hehe. I have also use the dunlop direzza, and the toyo r1r, all good tires but they don't have the grip of the rs3.


Good luck with your build, I honestly thing a e30 is not enough to compete nationally in STX but I commend you for trying, these cars can amaze you from time to time.

here's a pic of my car from a few years ago

[race2win]

Thanks everyone for the comments & suggestions. In regards to the Fat Cat Bilstiens, they will be rebound adjustable, definitely need that otherwise I wouldn't consider it. The Miata I drove to E-Stock wins last year at the San Diego National Tour & the 1st round of the Nor Pac Divisional has Fat Cat adjustable Bilstiens on it, they were fantastic...much better than the Konis I had on my personal E-Stock Miata the year before. The adjustment knobs are at the top of the shock like a Koni which is nice, & each quarter-turn can have a noticeable affect on handling. Fat Cat's success in Miatas is hands-down proven, with too many Tour & Pro wins to count, & quite a few National Championships...I'm very confident Shaikh can put together a competitive BMW package. Plus, they are autocrossers & know what is neccesary to run up front, & rebuilds or upgrades are easy.

I have heard nothing but great things in regards to AST, & I must admit I am drooling over the new 4150/4250's as well (especially with aluminum bodies). However, what is mainly holding me back is high cost (I'm guessing $2500-3000 for 4150s, & that's without camber plates), but also the "one-size-fits-all" valving, & at least for me, more difficulty getting support & rebuilds if needed. My target for shocks/springs in this car is no more than $2K, & that hopefully will include camber plates. This is for many reasons, but mainly to show that a simple cost-effective set-up can be competitive. In my career I have always done very well with simple shock packages, I want to continue that trend here. As I have said earlier in this thread, I want to provide an easy-to-duplcate set-up that other E30 owners can use on their cars. As good as AST, Motons, Penskes, etc. are, there just aren't going to be many E30 owners spending $3-5K on shocks for their $3-5K car.

So, back to spring rates...so it appears most people are running more rate in the rear when not using a rear bar. That being said, my initial thought is going with something like 650-ish in the front & maybe 800 in back?? Again, I want the car to transition great, so I am basing my numbers off what the ST & STS cars run.

I will admit to not being very knowledgable on the engineering of suspension design & all the geometry such as wheel rate, etc., so I could be way off base. I will be talking with both Fat Cat & Ground Control in the coming weeks to come up with a game plan, in the mean time keep the comments & suggestions coming!!