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Thread: Thinking about an E36 autocrosser

  1. #1
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    Thinking about an E36 autocrosser

    My wife and I drive an STX Mini Cooper. It is good even even if most days include a spin. We had a baby eight months ago and he just outgrew his lift-out bassinet style car seat. He is moving to a fixed rear facing child seat and there is no way I am going to be able to get him out of the Mini. Our autocross days normally start with all three of us driving to a grandparents house so my wife and I can have a day together. We are looking at replacing the Mini as a weekend/autocross car and found the E36 chassis. I have owned a 318ti and a Z3 Coupe but never one without trailing arms or with back doors.

    I am targeting a 75% street touring build. Cheapish coilovers and camber adjusters, sway bars, sticky tires, and a junkyard diff if I need one. Other than the standard E36 cooling system, bushings, etc, what breaks or wears quickly during autocross? I know in my Mini, we replace the front control arms at least once a year. If I go to a Hoosiers class, is there anything else that becomes a wear item unexpectedly? For example, do rear subframe or diff mount problems happen to everyone on sticky tires or do I need to get unlucky?

    At the street touring prep level, is there a big difference between a 325, 328, or M3? The M3 has more power and always comes with a diff but it seems like I am swapping out the rest of the parts that make it better.

    The main reason I am looking at street touring is I don't fit into E36s with stock seats. I am 6'6" with short legs (32" inseam) and a tall torso. I have test driven an E36 M3 with a sunroof and my hair was brushing the headliner without a helmet. I think I need another 2" of headroom but my wife is 5'9" so I can't just bolt a seat to the floor. Of the E36s, is there one that is more likely to come without a sunroof? A sunroof delete bumps me to Street Modified unless I do a crazy roof replacement.

  2. #2
    MINIz guy's Avatar
    MINIz guy is offline #buttstuff2k14 BMW CCA Member
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    I'll tough on somethings in my post but may miss a few things. I'm talking primarily STX non-M as that is what I have. M3 is STR.

    '97-'98 E36's have the option of no sunroof. Very rare and hard to find.
    '97-'98 non-M E36's don't include an LSD, and your option is a nice OS Giken or similar ($$$) or putting an E30 LSD into the E36 case ($$). I believe Z3's also have a torsen that's a 2.93 ratio. Basically, a diff is harder to come by.
    pre-'95 E36's all have sunroofs but finding a 3.15 LSD for it is easy.
    Power goes to the 328, but the 325 has shorter gears to minimize that power bump. The gearing helps the 328 out on faster courses (72 mph 2nd gear when tuned).
    Apparently subframes and RTAB brackets crack, mine hasn't after 3 years but I have all reinforcements and will do it preventatively after this year.
    I haven't had bushing or cooling system failure. I run all poly besides RTABs. Cooling system is stock but refreshed and I never have issues with it.

  3. #3
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    Thinking about an E36 autocrosser

    Quote Originally Posted by MINIz guy View Post
    '97-'98 E36's have the option of no sunroof. Very rare and hard to find.
    My 1999M3 has no roof.

    Quote Originally Posted by MINIz guy View Post
    Apparently subframes and RTAB brackets crack, mine hasn't after 3 years but I have all reinforcements and will do it preventatively after this year.
    RTAB Brackets don’t crack typically, the spot welded threaded insert pull out of the body. Add the reinforcement plates from AKG and others.

    Quote Originally Posted by MINIz guy View Post
    I run all poly besides RTABs.
    What RTABs are you running?
    OE Lemforder and RTAB Toe Limiters are a good choice.
    Could consider spherical here.

    I don’t recommend Polyurethane here as they can cause body nut failures - see above - RTAB rotates in multiple planes as suspension compresses/extends.
    [/quote]


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    Last edited by bluptgm3; 07-26-2019 at 12:20 AM.

  4. #4
    MINIz guy's Avatar
    MINIz guy is offline #buttstuff2k14 BMW CCA Member
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    Quote Originally Posted by bluptgm3 View Post
    My 1999M3 has no roof.
    Ah correct, the coupe's went to the '99 MY but sedans didn't.


    Quote Originally Posted by bluptgm3 View Post
    RTAB Brackets don’t crack typically, the spot welded threaded insert pull out of the body. Add the reinforcement plates from AKG and others.
    Also correct, I have the plates that reinforce the threaded inserts so they don't crack from the body and pull out. Definitely misspoke here and meant the pockets.


    Quote Originally Posted by bluptgm3 View Post
    What RTABs are you running?
    OE Lemforder and RTAB Toe Limiters are a good choice.
    Could consider spherical here.

    I don’t recommend Polyurethane here as they can cause body nut failures - see above - RTAB rotates in multiple planes as suspension compresses/extends.
    I have rubber RTABs with limiters, unsure of the brand. Sphericals in place of rubber bushings aren't allowed in ST trim.

  5. #5
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    Sounds like an M3 sedan is about $8K plus $3-4K for a slicktop (if I can find one). I am leaning towards the 325i. I can do a solid STX build just for the difference in prices. It also puts me in a pretty good chassis for DSP after the clutch goes. I really like single mass flywheels on E36s even if it sounds like a rod knock all the time.

    Is it possible to push back the inner sunroof panel while the sunroof is closed without breaking anything? I am trying to figure out how to drive the car during rainy events. On dry events, I can open the sunroof and turtle my head forward.

  6. #6
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    I'm not sure about USA, but in Canada the 318 seems to be the only cars that come without sunroof (slicktop) with exception of ultra rare slicktop optioned m3's. We also get Japanese market cars that are slicktops in 6 cyl, my daily driver sedan is 325 slicktop from japan.

    All medium case 188 diffs are interchangeable in e36's. I have 4 wreckers yard LSD diffs (row52.com can help you find a donor close to you and www.mdecoder.com will let you know if it had LSD option) . There is a 6 bolt CV style input flange on the pre 95 m3's only (easy to change) also there is a bunch of other cars that use the same ring and pinion that can be swapped with different ratios that aren't available in e36. There is also custom ramp's available to change the lockup. Basically the e36 is the last car you can play with the diff for cheap. There are plenty of threads cover diff mods.

    I'm 6'4" with a long torso so I know your pain. Some helmets are shorter that others. Slicktop definitely helps. I believe some stock seats go lower than others. Can't remember which one's (power or manual).

    There are also some different steering racks available for the e36. Fast linear z3 racks are great for autocross, if you are lucky enough to pick one up for cheap they are direct drop in.


    Good luck

  7. #7
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    I am building to a class so I have to be careful with diffs. To be legal in STX, I need a diff that fits within a stock casing and be a ratio available for the specific trim level on the model year of the car.

    I just ran into a similar problem when setting up a 318ti. Limited slip difs in that car use a unique diff case and a rare ratio (3.45). The medium car Z3 automatic diff with a torsen and a 3.46 ratio wasn't legal for the class even though it was awfully close. E30 small cases also weren't technically legal due to a different case. I ended up buying something from one of the online diff shops because a ti diff casing with a limited slip carrier plus a rebuild was about $1200. Now, I am a little gunshy about the 328s. I would rather buy a junkyard diff and spend more money on shocks.

    row52.com looks pretty cool. I haven't used them before. I have found that car-part.com has pretty good coverage in my area as well.

  8. #8
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    The medium 188 cases are all the same and the 328's did come with LSD's in some markets I believe the early ones in cold weather markets. You just need the correct ratio. Real oem lists the LSD included in the 328 in Europe and USA markets so it would be legal to swap one.

    Something worth considering, 328 has the better zf transmission the 325 has the getrag that's made of glass.

  9. #9
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    This is my 128i STX car:



    We recently came 3rd/21 at the SCCA Packwood National Tour behind another 128 - it is a great car for the class. It is also a fantastic driver - awesome stereo, lots of torque, etc.

    Highly recommended.

    -Mark

  10. #10
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    Quote Originally Posted by guymandude View Post
    The medium 188 cases are all the same and the 328's did come with LSD's in some markets I believe the early ones in cold weather markets. You just need the correct ratio. Real oem lists the LSD included in the 328 in Europe and USA markets so it would be legal to swap one.
    To be STX legal, it needs to be a 2.93 ratio in an E36 medium case. I believe those are quite rare. $2K is the going rate for a clutch based lsd from the various online vendors. Buying an open 2.93 diff a limited slip diff with the wrong ratio and swapping over the carrier is not much cheaper. Rebuilding diffs is outside of my skillset so I would have to pay someone to do it.

    - - - Updated - - -

    Quote Originally Posted by lowside67 View Post
    This is my 128i STX car:

    We recently came 3rd/21 at the SCCA Packwood National Tour behind another 128 - it is a great car for the class. It is also a fantastic driver - awesome stereo, lots of torque, etc.

    Highly recommended.

    -Mark
    I am looking for a sedan so I can get the baby into a rear facing child seat in the back. Otherwise, I would keep the mini.

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