Thread: 2 step anti-lag E46 M3
10-24-2010, 06:18 AM #26
I think with reinforced axles, driveshaft and driveshaft mounting the rear end should be fine. Make sure to have rubber bushings and no solid mounts on suspension parts. Also a big tire at the track will help alot as well.
10-24-2010, 01:07 PM #27
I have been building drag cars for 20 years now. I have some prior experience with IRS on my 64 Bug I raced. To solve wheel hop we used what was called a "Kafer Bar" which was basically a torque arm. http://www.csp-shop.de/technik/pdf/deeng/20917.pdf
Problem with the E46 M3 is there it very little aftermarket for this type of setup because the M3 is geared for road race, not drag race. A good example are the newer Cobra mustangs that come with IRS. Obviously American muscle will end up mainly on a drag strip, not a road course. There have been several aftermarket solutions for IRS wheel hop for the Cobra, but most simply swap out a live axle from a GT.
Bottom line, if your serious about drag racing the M3 with the power levels we are putting down, the IRS will never be reliable without major modifications to its structural mounting and range of motion. From what I can see from my research, you can't have a car that will be reliable at the drag strip and reliable at the road course. At some point I'll have to make a decision where my car will spend most its time.
10-24-2010, 01:16 PM #28
I had briefly considered seeing if HPF would work with Chassis Engineering in Florida to come up with a "bolt in" live axle solution, but given the limited market for such a product the idea kinda fizzled as quickly as I thought about it. If I decide to go "all out" as a drag car, I would probably work with Chassis Engineering though to come up with a solution.
Problem is there is just simply not enough market interest in supporting "drag mods" for the E46 M3.. so very little R&D has been done to resolve wheel hop.
10-24-2010, 01:21 PM #29
10-24-2010, 01:22 PM #30
10-24-2010, 01:34 PM #31
10-24-2010, 01:37 PM #32
10-24-2010, 11:57 PM #33
Mike R's E36 puts down 900whp and it ran mid 9's. Hes running a BMW IRS, ive spoken to him and it seems like the only way to keep these cars together at the track is with big soft tires, rubber bushings etc.... Hes done some diff reinforcing, drivfeshaft mods and axle mods as well.
10-25-2010, 01:20 AM #34
A ford 9 inch would be a great rear end of choice, hell even a ford 8.8 inch is plenty. These turbo inline 6s dont launch hard off the line trust me, you want to see hard; watch a nitrous 410 stroker leave the line cutting 1.3 60 foots all day long. And those can be done on an 8.8 housing with 31 spline mosers or strange engineering axles choose your pick. Either way I agree with ccykes, if you want to come off the line without crying little a girl inside each time you drop the clutch you might want to go with a ford rear end.
Either that, or spend lots of money trying to keep the stock BMW geometry and optimize it for the strip.Some people live long, meaningful lives.
Other people eat shit and die.
I'm not racist, I hate everybody equally; especially fat people.
10-25-2010, 05:30 AM #35
10-25-2010, 09:57 AM #36
10-25-2010, 09:59 AM #37
10-25-2010, 12:03 PM #38
I have ran them in 17's. I tried them on the street for awhile, they were not good. Needs lots of heating, was a little squirly (Ps2 radial 19's up front). But this might be the tire I try for the 1/4. It may be possible to find a 16'' wheel that will fit in the rear. We have to do some research and trial/error. The rear stock rotor size is 12.9 inches.
They were definitely shorter then the MT ET Street Radial II I have on the car now. And the tires I have right now are amazing for the street, they stick hard. But for the track I think the below tire might do the job. Deflated they might wrinkle well enough for a launch that will absorb all the stress.
MT ET Street 26X11.50-17
10-25-2010, 12:06 PM #39
Those are the tires I plan to run on the strip though, when hot they should grip incredibly insanely well. If not, I'll have to modify the rear brakes and go with a 15 or 16.
10-25-2010, 04:03 PM #40
10-25-2010, 04:12 PM #41
10-25-2010, 04:33 PM #42
They have ran 9's with 16'' setups. The 16" tire size they use is actually comparable to a 17'' tire we can put in our fender (since our fender is larger). I have a 27+ inch tire on my car right now, that is pretty large. So were not far off with the 17'' setup. You don't need a 15'' wheel.
10-25-2010, 04:38 PM #43
10-25-2010, 05:04 PM #44
10-25-2010, 05:52 PM #45
10-25-2010, 09:49 PM #46Member
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10-25-2010, 09:56 PM #47
10-26-2010, 02:04 PM #48
Wow...I feel like an old guy now.
2006 - First E46 with a real "drag tire". 1.7 second 60ft times.
2007 - First E46 to "tub" the rear wheel well
2008 - First E46 with all solid engine, drivetrain, and suspension bushings
2009 - First E46 to run 1.6 second 60 ft times
The guy that built my 14 point cage has a car that runs low 1.3s, and I've recently had a chance to compare his launch data to mine. In the first 30 ft we're even, but then my torque fell off over 5500 RPM and I shifted to 2nd 40ft out. So in theory, I know what a 1.3 second "launch" feels like. And to date, I've never seen anyone twist the output flanges on a BMW diff the way that the 330Ci did. Also, every BMW I've seen run 1.6 or faster 60fts has had substantially more power; double in most cases.
I credit the tire (16" wheels, MT ET Streets, and 12 PSI), suspension, and bushings being a big part of my launch.
Did I break stuff? Yup. But there's just no other way to figure this stuff out. The professional race team that I crewed on from 2006 to 2008 had 10 times more diff, halfshaft, and transmission problems than I did...and probably the rest of the "BMW drag racing crowd" put together. And stuff never seemed to fail much when testing...it always seemed to be at the worst time. (I've got in car video of some really bad scenarios) What I'm getting at is that we can discuss this stuff till we're blue, build and street drive it for years, but the race track will kick your ass.
Running a 2 step/ Anti-lag may sound cool in the driveway, but until the rest of the drivetrain and chassis can be addressed, it's playing with fire.
Chassis? Subframe mounting points? Nope. One part of my car that we put a bit of time into was the rear trailing arm "buckets". They will actually tear out if you run solid bushings ect. for very long. And then there's the bracket that holds the rear trailing arm into the "bucket". Have a good look at them if you get a chance. They are a stamped steel piece that is spot welded. They don't like solid bushings either. Back to the bucket: We actually cut through the rear seat area and tied them directly into my roll cage.
BTW, I bought a 4 link rear end last spring. Has anyone seen my 330Ci lately?
10-26-2010, 02:12 PM #49
10-26-2010, 02:27 PM #50
Your work is a testament to how hard it is to do it on an E46....