E90 M3 for STU Auto-x

[Derekb]

Ok I've decided to do a semi-serious setup on my M3 Sedan.

Here's what I've got so far:

E90 6mt Sedan no-sunroof - I know not the perfect STU car....

EDC Dampers with custom coilovers and camber plates. Will try various spring rates during testing

Dinan Intake

Dinan/Brembo 380/345 Kit. Already put on the car for track days

75mm stud conversion

Dinan Exhaust

Dinan Strut Brace

Dinan 3-way adjustable front swaybar with custom end links

Dinan tune

Rear sway bar TBD

Custom Diff TBD stock for now

I am undecided on swapping all the bushings out per the rules. Anyone done this?

Other things up for consideration are seats/harness setup. Like everyone else still waiting for the Schroth availability. I imagine the stock seats weigh a ton.

HRE 18x9.5 R43 Wheels with 285/30/18 Hankook RS3

Can anyone share their thoughts? Would like to shorten the learning curve.

Thanks,
Derek

[Richbot]

If you're semi-serious and/or serious, the EDC dampers aren't going to cut it. Think JRZ, Moton, etc. After tires, spring rates, and getting enough camber, the dampers are the biggest bang for the buck IMO, and the EDC dampers are trick and all but they are still inherently compromised for performance driving. On top of this, the springs you decide work best with the EDC dampers might actually be far from optimal and you'd end up starting over when you finally decide to switch to a good racing damper. Always better to buy once than twice. After tires, this is where I would spend the big bucks. Worry about seats, bars, diffs, exhaust later.

I wouldn't bother with a rear sway bar, an adjustable front with good spring rates all around should be fine.

The 285/35-18 RS3 might be a little tall for the front (there's no 285/30-18) but I bet you can get it to work with a little offset and ride height fiddling, wwsjd or whatever his name is runs them all around on 10.5's. If they won't work the Yok AD08 comes in 285/30-18 which would be a little shorter for easier front fitment and better gearing. Also, the car can fit 10.5" wheels all around, since you can't go wider on the tires, widening the wheels to a 10 or 10.5 might be beneficial.

You might want to look into the STU brake rules, the rear brakes are probably not legal because they're smaller in diameter than stock. Might need to go up to the 380mm brembo in the rear to be strictly legal, though I doubt anyone would protest you on that point (or protest you at all on anything, for that matter).

Losing weight is going to be key, get those seats out of there ASAP. A 6speed non-sunroof E90 isn't that bad of a place to start, it's still lighter than a lot of loaded-up E92's out there. If the Dinan strut brace is heavier than stock, get rid of it. The car comes with a perfectly serviceable brace setup from the factory, and the rear one does diddly-squat. Don't forget about the weight loss opportunities in the mid-section exhaust, there are catted x-pipes out there that are STU legal, though the Dinan isn't one of them

The HRE's are nice but are you sure they're the lightest wheel available? I would look at the Volks if you're spending that kind of money, unless you already have the HRE's.

From a bushing standpoint I'd think you'd be better off spending the money on the above stuff than worrying about those. It's a relatively new car with relatively stiff bushings from the factory.

[Z K]

I run my M3 in STU class with SCCA. The car is stock and I am about 3 seconds off the lead cars in the class (E36 M3s) on a 50 sec course.

I think as I get more familiar with the car, some modifications and stickier tires, I can get close to the top runners. I used to be with the top finishers in the STU class with my previous car (Evo X) and won a few events including one of the NorPac Divisional days in it. Obviously the M3 is a very different car to drive.

You don't need to do much to the car to be competitive in the M3. STU class in the San Francisco area is not as competitive as on the National level. It is dominated by E36 M3s and some Evos. Who your competition is depends on which clubs you run with.

[Derekb]

Thanks for the feedback. I realize EDC dampers aren't optimal but I am working on making them as good as possible.

HRE wheels are already here so I don't want to invest more money. Got them for track use.

Didn't know about Hankook sizes. May have to go with a 275. Probably will fit on the 9.5's better anyways.

Having a catted x-pipe made for me right now.

Seat options are up in the air. The car is still driven on the street so I need a solution that works there and isn't crazy expensive (i.e. bmw performance seats)

I think I'll get it to a decent point and see how it does.

[Derekb]

ZK what setup are you running?

[dcstep]

Is a final drive change allowed in STU? If so, the 4.10 is fantastic on the E92 6MT. It still gives you 72-mph in second and more response out of tight corners. You might want to consider the E93 rear bar to stiffen up the rear just a little and give better rotation.

I'm running the stock EDC with Dinan camber plates and springs. I run -2-degrees in front and -1-degrees in back. I use 275-35-18s on 18x10" APEX wheels. If you could fit larger tires on, it would be very good.

Dave

[Z K]

Originally Posted by Derekb

ZK what setup are you running?

As I mentioned in the my last post, my car is stock. I maxed the camber out in front at -1.5 degrees and -2.0 in back. I think I may need more front negative camber as it is rolling onto the sidewall under cornering.



Here's one of my runs for last year's slush season. The PS2 just don't cut it. Instant wheel spin under hard throttle.

I recently got the KW sleeve over kit and am planning on corner weighting the car and setting that up. Also planning on some stickier tires once the stock PS2 wears out.

[Maypo]

That's a nasty little course. Where was that held?

[Be Stock]

Originally Posted by dcstep

Is a final drive change allowed in STU? If so, the 4.10 is fantastic on the E92 6MT. It still gives you 72-mph in second and more response out of tight corners. You might want to consider the E93 rear bar to stiffen up the rear just a little and give better rotation.

I'm running the stock EDC with Dinan camber plates and springs. I run -2-degrees in front and -1-degrees in back. I use 275-35-18s on 18x10" APEX wheels. If you could fit larger tires on, it would be very good.

Dave

A final drive change is not allowed in street touring classes. Also, I don't see how a 4.10 final drive will give you 72mph in second gear without increasing the rev limiter. A stock E9x M3 with 6MT and 3.85 FD can hit approx 71 mph in 2nd with OEM size rear tires. Your have a shorter FD and smaller diameter tires.

[Richbot]

Yup, the factory gearing whether it's DCT or 6-speed is just about perfect for autocross. Not worth it even if it was legal, IMO.

[Z K]

Originally Posted by Maypo

That's a nasty little course. Where was that held?

It was at the Oakland Coliseum.

[CSBM5]

Any updates on running an E90 M3 in STU?

[dcstep]

Originally Posted by Be Stock

A final drive change is not allowed in street touring classes. Also, I don't see how a 4.10 final drive will give you 72mph in second gear without increasing the rev limiter. A stock E9x M3 with 6MT and 3.85 FD can hit approx 71 mph in 2nd with OEM size rear tires. Your have a shorter FD and smaller diameter tires.

Increase the rev limiter.