Autocross nerd thread: The Ultimate E9X A-Stock SCCA Autocross Build?

[dcstep]

ZK, nice of you to post your video.

You really need to take a course that gets into appropriate racing lines, managing weight transfer, etc. From what I see in your video, you could probably gain most of that 3-second deficit in a couple of outings, but you'll have to focus and concentrate a lot to totally close the gap. Still, it looks like you're having fun and that the whole point. Keep at it and try to get some instruction from successful drivers.

Dave

[Z K]

Originally Posted by dcstep

ZK, nice of you to post your video.

You really need to take a course that gets into appropriate racing lines, managing weight transfer, etc. From what I see in your video, you could probably gain most of that 3-second deficit in a couple of outings, but you'll have to focus and concentrate a lot to totally close the gap. Still, it looks like you're having fun and that the whole point. Keep at it and try to get some instruction from successful drivers.

Dave

I've been autocrossing for 14 years. SCCA Sacramento Region Champion in ST-X class back in 2002. SCCA Enduro ST-X Champion 2002, SCCA NorCal Divisional 2nd place in ST-U in 2009...

It was actually my first runs in this car so I was not used to the lack of grip and weight shifting from a stock car. It was very different than a car set up for autocross class-specific competition. I got better.

Those runs were more like 7 seconds from the usual people I run with. I just posted it to show my learning curve when starting.

Here is my 2nd event in the BMW. A lot smoother.

Here's an old event in my previous car. Suspension is set up with HKS Hipermax III coilover suspension, custom alignment specs and set up with AD08 Neova tires, dyno tuned for 380hp, 400 ft/lb torque on stock boost map, BBS lightweight forged wheels.

[Maypo]

Originally Posted by dcstep

The big advantage we have is the broad, flat torque curve, making it easy to adjust and control power through the tight sections and slaloms.

Plus, I think, a smaller package with better dynamics.

In ESP I think I'd go with the Mustang GT with the 3.73 FD and Brembo brakes. Of course, in ESP you'll have to contend with my old friend Mr. Madarash, but it's a hell of a class... Their basic suspensions and high torque work VERY well on flat AX circuits. Add tire and go...

IF an E92 were classed in ESP, then a very serious lightening would possibly bring it into competitiveness, but it's starting behind in almost every way these days. More weight and less torque means... slower. HP counts for very little when you spend more than half the lap in the middle of the torque curve.

Dave

Yes, if I were going to choose a car specifically for ESP, it would almost certainly be the new Mustang. I don't have the idea of changing the class paradigm, I just like the idea of throwing it down with the Detroit Iron. The M3 should make a good showing.

[Maypo]

Originally Posted by Richbot

Maypo- we should compare notes on the a6's. I will have the fitment questions answered in a few weeks.

Sounds good. I did an initial fit-check with them, without driving the car, and they cleared in front on the stock rear wheels, whose offset difference is legal -- so I think we will be good to go.

[Richbot]

If they fit up front on the 9.5's they'll definitely fit on 8.5's so that's good to hear. You probably know this already but make sure you use the 8.5's up front if you're running Stock, the offset difference is fine but the width isn't. I did some measuring now that I have the 295's in my hands and they're only about 5/8" wider than the 275 Contis I have on the rear of the car, and there's more than 1.75" of extra clearance back there. Looking good for the 315's. My measurements tell me ET29 is going to be just about perfect in front but the rear might need more like ET27 or so, which would put me in an interesting custom spacer predicament with the tire rack ET35 9.5's. Too bad those BBS Motorsport rear wheels from the GT4 are 10's as they would be perfect with a 15mm spacer.

[mkPOTO]

would vs motorsports e92 scca race car be something close to what you are looking for?

[Richbot]

Touring 2 is prepped to a totally different ruleset. If Showroom Stock still had a class for cars as fast as ours, cars prepped to those rules would be allowed to run in SCCA Solo2 Stock class. Touring allows a lot more stuff so those cars go in their respective Street Prepared class.

I am watching their build closely though, partly because I was somewhat involved in getting the car classed in T2 and partly because they race in my neck of the woods and I'll get to see the car on track when I'm racing the SRF.

[Maypo]

Originally Posted by Richbot

I did some measuring now that I have the 295's in my hands and they're only about 5/8" wider than the 275 Contis I have on the rear of the car, and there's more than 1.75" of extra clearance back there. Looking good for the 315's.

There really is oodles of room in the rear. As seductive as 315 rears would be, I expect the 'square' setup (295s all around) will prevail, on most courses anyway.

[Richbot]

That's just your tire guy's laziness talking. I agree the 295's all around should be pretty good, especially with the stock suspension setup. That's why I won't be sad if the 315's won't work, but I think they will. And I'd rather start with as much tire as possible and tune my way into the balance with alignment, bar, and shocks than do the same with the 295's all around and have to start over if I find out I need more tire. I have a feeling the 315's with a little more camber will be helpful in slaloms where this car tends to wag its tail a little too much.

[Maypo]

Originally Posted by Richbot

That's just your tire guy's laziness talking. I agree the 295's all around should be pretty good, especially with the stock suspension setup. That's why I won't be sad if the 315's won't work, but I think they will. And I'd rather start with as much tire as possible and tune my way into the balance with alignment, bar, and shocks than do the same with the 295's all around and have to start over if I find out I need more tire. I have a feeling the 315's with a little more camber will be helpful in slaloms where this car tends to wag its tail a little too much.

Well, the setup most people use is "square"; until the PtW ratio, or weight distribution, or personal tuning preference dictate otherwise. For the M3 I have been trying to see what the FS and ESP cars are using, and I think their preference is Square. In any case, I consider the forthcoming tire choice merely a starting point... And, you may be right about the specific help the 315 would provide in slaloms.

[Richbot]

Theres always 315/315...fender liners can be replaced

[Maypo]

Originally Posted by Richbot

Theres always 315/315...fender liners can be replaced

Lol - technically 'square'!

You know, granted the efficacy/legality of mounting massive tires on skinny wheels, I have always found it aesthetically offensive. The purist in me favors a rule that would keep tire section widths close to wheel widths.

[Richbot]

I agree. The showroom stock class rule seems appropriate. Max 20mm variance in section width compared to stock would still give people plenty of leeway to find a tire that works without the pinched silliness

[Maypo]

Z K, did they repave Golden Gate Fields? I was there in '08 and it was pretty bad here and there.

[Z K]

Originally Posted by Maypo

Z K, did they repave Golden Gate Fields? I was there in '08 and it was pretty bad here and there.

SCCA lost that venue. Lots of complaints from the field owners about the cars being too loud and bothering the horses there. That surface has a lot of grip but eats tires as you know... they never repaved it.

[Maypo]

So, is there a replacement site, or just more events at the others?

[Z K]

Originally Posted by Maypo

So, is there a replacement site, or just more events at the others?

They just host it at a couple of places: Oakland Coliseum, San Francisco Candlestick Park and Marina Airport in Monterey. Candlestick Park is by far the worst autocross site ever. There's bumps, jumps, grass growing from the ground, glass and bottle caps all over the lot. It's more like a rallycross course than autocross. Marina is pretty far from San Francisco so there's really only Oakland left.

[m3kerry]

Originally Posted by Richbot

I race all over the country, are you a club racer too?

I will be autocrossing with St Louis region and i plan to hit the lincoln tour

Sorry if i was douchey but that was a little bit of an elementary-level comment.

Back before you thought i was a smartass, before the e92 was a twinkle in bangle's eye, the e36 m3 needed a stiffer front bar in stock class to keep the suspension in its happy place. Too much bump travel and the suspension starts to gain camber. The consequences were better tire wear, better transitions, and no loss in steady state grip. This scenario plays out over and over in Stock. When roll stiffness is difficult to come by, the front bar can be a big benefit on a variety of cars including bmw's. The e9x is a better design than the e36 but it still stands the tire up during big bump travel especially with the wheel turned.

By the same token, more front roll stiffness means less droop on the inside rear. This means less weight off the inside rear on accel.

Come on down to stl or come out to Lincoln and run ESP and see if you can raw time me with all the stuff on your car. Loser buys the beer.

This is all true, sadly I built a B stock e36 m3 the year after the rx8 took over.

Lord, save yourself and your money on this build. Oh, it will be fun, but you are going to need a National trophy level driver to make a case to the seb, so who are you going to put in the car? (Andy?)

You will have some of what you are seeking in a stock this year with the American v8's in the boss 302 is in a stock and probably just as out gunned as the e90 m3.

If you run the mid-div events in kc and Stl, you will get to bump heads with a 1m with at least one driver that is picked to win his class at nationals most years in sports car magazine.

I think you will have fun. I only autocrossed in an e90 once and the arm rest crowded me. How do you feel about the seat in the e90? Do you have room/space for yor arms? It kept bumping my elbow.

[Richbot]

Originally Posted by m3kerry

This is all true, sadly I built a B stock e36 m3 the year after the rx8 took over.

Lord, save yourself and your money on this build. Oh, it will be fun, but you are going to need a National trophy level driver to make a case to the seb, so who are you going to put in the car? (Andy?)

You will have some of what you are seeking in a stock this year with the American v8's in the boss 302 is in a stock and probably just as out gunned as the e90 m3.

If you run the mid-div events in kc and Stl, you will get to bump heads with a 1m with at least one driver that is picked to win his class at nationals most years in sports car magazine.

I think you will have fun. I only autocrossed in an e90 once and the arm rest crowded me. How do you feel about the seat in the e90? Do you have room/space for yor arms? It kept bumping my elbow.

<- past trophy winner. but Andy is certainly welcome. The list of people i owe codrives to is a long one.

I havent noticed any issues in the interior it fits me pretty well. Seats are great much better than the sport package seats in the non-M cars. The shoulder support makes a big difference

[CSBM5]

Originally Posted by Richbot

The competition in AS is the Cayman S, several base Corvettes, and lots of other proven cars that aren't showing up because people seem to think the Cayman S is an overdog even though the 'vette won it all this year, and because the costs aren't really any better than Super Stock, you just go a lot slower. I'm going into this knowing it's an uphill battle in AS.

I've always wondered how the 2004 40th Anniversary 911 would fare in A-stock. It has the X51 power kit engine, stiffer springs (Mo30), and importantly a limited slip diff that Caymans and other 911s in A-stock don't. I was pondering using as much of the setup experience from SS GT3s as possible (tires, front bar, alignment, etc) also. I just drove my daughter's fiance's 40th in an autox last month, and I'm thinking this car might just be a hidden (from the radar) possibility if properly prepared (and driven of course). Anyway it was a fun car (but was on BFG street tires) and was the first time I've driven a Porsche in an autox since 1976.

Second thing that comes to mind is front camber on the M3. Having had a number of years experience with an E46 ZHP in D-stock, the front camber issue is the biggest handicap -- all from a tire wear standpoint ($$$). The most the E46 can get is just a bit over -1.0 up front, maybe -1.2, with the pins out. We (daughter and I co-drive it a lot) were "fortunate" to experience cording outside edges of brand new A6s (~$275 each) in 16 runs. The V710 is a bit longer lasting, so I'd look at those if I was doing this M3 challenge. We ended up using BFG R1s to simply have fun and gets lots of runs out of them at local club events (which don't work too bad at all in typical summertime 95+F temps here).

Good luck with the M3. I look forward to reading about your experiences with the car.

Regards,
Chuck

[Richbot]

In light of the "fun" with cording hoosiers on M3's in the past the thing I'm counting on as I've said before is that the simple strut E46 front suspension design had pretty bad geometry compared to the E90's more complicated design. This car will still eat outside edges but it shouldn't be near as bad as the old strut designs were, plus I've already been able to get 1.6-7 degrees from the front with the pins pulled and I haven't even started loosening things up and yanking on it yet. But then it's a heavy car too. Oh well, here's hoping. Can always just flip them on the rim if they look ugly, I'm hoping I can get ~30 runs out of them before flipping them. The V710's are good tires and I have experience with them, that's a potential backup plan but I hope I don't need it, as the A6's are just plain better in most situations.

I think that 996 would be good too, more people need to bring them out. If SS wasn't so fun and well-populated I think AS would be a lot more popular but here we are.

In case anybody is actually reading this thread for useful information, the 30mm RD Sport front bar is hollow but it's still about 1lb heavier than the stock bar. The stock 26.5mm front bar is hollow and has a more severe bend to clear the tie rod than the RD Sport bar. I think most of the weight difference comes from the big pieces of very thick plate for the adjustment holes. Interestingly, the RD Sport bar on its stiffest setting uses only about 1/2" shorter moment arm than the stock bar, and at full soft it's close to 1.5" longer than the stock moment arm. I'm using the Turner adjustable endlinks to take the preload off the bar, there was a surprising amount of preload in the stock bar for some reason. Interested to see what the cross weight looks like with the endlinks adjusted properly. 6 different stiffness settings should give me plenty of leeway to screw something up.

Front bar was a big improvement on street tires. Lots more responsive to drop throttle in sweepers now and the car is more predictable in transitions (used to like to snap out in quick low-speed 2nd gear transitions). Gives me hope that balance might be close when the car tightens up from the extra Hoosier grip. Had it on the intermediate setting to start with, which is about 30% stiffer than stock

Took me 30 minutes to get the preload out of the bar with the adjustable end links but it was worth it, cross weights are better now too. Very close to 50%

[Maypo]

Good to hear the bigger bar has settled the car down. I installed mine a couple of months back, but haven't had it out to an event since the installation. Its behavior on the street has seemed to foreshadow your experience, but there's no replacement for 10-tenths testing.