Cheap Track Car Preparation Questions

[MadManInTheBox]

Hey guys, my 2009 328i (auto trans) is no longer my daily, and is now beginning the process of becoming a track toy. I took it to one track day, and the biggest and most immediate issue is the transmission.

1) It has the infamous torque converter shudder, and has been doing it for about a year and half or so now. I haven't been worrying about it, but how will it effect it under track conditions? Mine only does it at partial power at about 2000 rpm. When really on the throttle, it doesn't do it. My question is: Can I replace the fluid with a higher/lower viscosity trans fluid to help it? I don't drive the car around much anymore, i just want it to survive the track. Either that, or how long can I expect it to survive thrashing? It hasn't gotten any worse since it first appeared, and has been pretty consistent.

2) But the biggest issue is that the auto trans likes to be in exactly the wrong gear, every time. Trying to use the Tiptronic didn't really help, as the transmission decides to ignore my requests about 75% of the time. Is there anything I can do about that? A tune? Can I splice into the wires to intercept the signal somewhere and hook it up to some paddle shifters? Mainly, I just want the transmission to stay in the gear I ask it to, all the way to redline.


Now, I know what you're all going to say. "Just manual swap it!" No. I'm not trying to put that much money or effort into this car just yet. I have another project that's getting the majority of my time and money right now, I just want to see if there's anything relatively inexpensive and straightforward I can rig up for some casual track time in the meantime.

[eseeling]

I used Dr. Tranny shudder fix in my subie and it worked

[SS Ball3r]

good pads and all fluids changed. You may look into xhp flash tuner for the trans as well. There is likely a flash for the 328i that you could use to allow more a more "manual" shift through the autobox. If you don't have the paddles currently, I believe you can retrofit them as well. I know there are some companies that offered that for the e60's, and I would venture to guess that there are some for the e9x's as well.

[MadManInTheBox]

I read ab bit about the xhp tune. I might look into it more. Ditto for the paddle shifters, I didn't even think about that. However, my main issue is it upshifts when near the rev limiter, and i usually want it to hold the gear. Does the xhp solve that?

[SS Ball3r]

Xhp can allow you to hold the revs and shift when you want too

[lucas999]

I used Dr. Tranny shudder fix in my subie and it worked

I used this too in my old 740iA and it solved the shudder issue.

[328 Power 04]

Does xHP work on the GM transmissions??

[MadManInTheBox]

Seconded!!

[SS Ball3r]

Does xHP work on the GM transmissions??

That's a great question, I hadn't even thought about that as i have a 335i (manual at that). I would give the company a call or email them: https://www.xhpflashtool.com/

[MadManInTheBox]

I never did do anything for the trans, but I did go to an autocross over the weekend. To be honest, the transmission wasn't as bad as I thought it would be. However, that might have been because I could hardly keep the back end from misbehaving.... Pirelli all-seasons are great tires for daily driving, but not for autocross. I already have had a box with new rotors and pads sitting in my living room for a few weeks, I just already knew I'd not have time before the event to get them on. There's a Time Attack event at the end of the month, and I'm hoping to have the pads and rotors on, as well as new tires. For the class, I can have any currently available 200 treadwear tires. I'm going to get a set of Federal 595 RS-RRs. Hopefully, that'll help keep the back end in line. I'm also considering welding the diff up. It wouldn't be as good as getting a proper LSD, but it'd be a hell of a lot cheaper and easier, and better than an open.

[MadManInTheBox]

I'm bored, so here's a bit of an in-depth update:

So I've decided that for this year and maybe next year, the car is going to be in FS for SCCA autocross, and S4 for SCCA Time Attack. The rules are much more restrictive for the autocross class, but they're similar enough that the car in FS trim should be fine for the time attacks.

The biggest thing the car needs is new tires. I didn't have a chance to get new rubber before the lockdown, but it's #1 priority. Probably going to stay with the 225x18 Federal 595 RS-RR i have on my other cars, as they've done me good so far and are unbelievably cheap for the performance. I have been eyeing the RE-71Rs, though, and if I could find a good deal, I'd be all over it. For both classes, the restriction is 200tw, and for FS they have to be on stock sized wheels. I already have Touren TR70 18x8 wheels, and they're pretty light, but could better. Not gonna dump the money into wheels for a slight decrease, though.

Immediately after that, the new brakes and rotors are going on. I got the ECS performance kit, which has the ECS drilled and slotted rotors and Hawk pads. I know drilled and slotted aren't necessary for auto-x, but I want to be able to take it from the short track to the big track without having to do much work. Those, plus a proper high-temp brake fluid flush, and I'm confident the brakes will perform well and last.

I can't really tell for sure what the chassis will need in order to get balanced until the chassis, and not grip, becomes the limiting factor. I already know the balance is pretty good, leaning slightly towards oversteer. For FS class, you're only allowed one replacement sway bar, so doing a front sway bar should settle the rear down. The car feels nice and stiff, so an underhood brace or other reinforcement doesn't seem necessary. I also want to start replacing every bushing I can with poly. I can't do solid aluminum, but poly should be more than enough to bring more feel to my hands.

I also decided to just weld the diff up, rather than drop several hundred dollars on an LSD. We've done comparisons using one single car, open diff then welded, on the same course, running enough laps in either configuration that we are confident with the results, and welded is decisively faster than open. It's actually quite close to a nice LSD in terms of lap times, if you can get used to the slightly skiddish back end behavior.

As for the trans, I've decided to not to anything anytime soon. I finally heard back from xhp about the trans tune, and they don't offer anything for the GM trans. What me and my co-driver decided is that we're just gonna rock it as is until there's a serious problem, then do a manual swap somewhere down the line, if and only IF the car has shown that it has the potential and will be worth the time and money, and the transmission is the only thing holding it back.

I'm also planning on getting a welded in harness bar or maybe even a half-cage, combined with a proper seat and a harness. Safety is cool, kids. (Is anyone else honestly excited for the SA2020 helmets to finally go on sale, or is that my racecar nerd showing?) According to the SCCA rules, that would allow me to strip everything from behind the driver's seat back, as well as swap the steering wheel. (Quick release plz).

Oh, and it's getting a rattlecan paintjob. Stay tuned for that, as we're true artists with spray paint, and what we have planned is DOPE.

- - - Updated - - -
Forgot to mention the exhaust. I'm allowed to do cat-back, but instead of spending a lot of money on a lightweight system, I cut the muffler open, removed about 25 lbs of internal baffling, then welded it back together. It barely sounds any different, but it weighs less, so I guess it's a win.