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Thread: BMW Z3 Coupe - Rally Build Log

  1. #1
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    BMW Z3 Coupe - Rally Build Log

    I will be documenting here the build of my 1999 BMW Z3 Coupe into a rally car. The plan is for a relative slow build over the next year, with some testing in 2018 before competing in NASA, Rally America and/or American Rally Association events. I currently compete in a 1999 Subaru Impreza RS, but I am looking forward to the challenges of competing in a RWD rally car.

    Here is the starting point:





    The car's body is in good shape. Previous owner also did a bit of the preventive maintenance in the cooling system. Interior was quite neglected, but all of it will be gone for the rally build.

    - - - Updated - - -

    First step in the build was to gut the interior. I was impressed with how well the interior is put together - it does not use a lot of the one-time fasteners that tend to break when you pull apart - instead most of the interior parts are either screwed or bolted in place.



    - - - Updated - - -

    Another angle:

    Last edited by sebastianrally; 01-08-2017 at 08:31 PM.

  2. #2
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    This is very relevant to my interests. Looking forward to the progress.

  3. #3
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    Did you buy this from Billy with the red E36 sedan?
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  4. #4
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    Yes, that is the one.

  5. #5
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    Nice! He's a good guy, I lusted after this thing hard but would have needed most of an interior plus fixing all the other little quirks to make it a daily driver for me. Glad it's being used in a better way!
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  6. #6
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    Quote Originally Posted by Brake_L8 View Post
    Nice! He's a good guy, I lusted after this thing hard but would have needed most of an interior plus fixing all the other little quirks to make it a daily driver for me. Glad it's being used in a better way!
    I think this one was a step too far to return to it stock glory... It will live a different life now.

    - - - Updated - - -

    Sometimes it is the little things that keep a build going. Since the dash needed to come out to build the cage, I went ahead and flocked the dash this weekend.

    IMG_1313.jpg

  7. #7
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    Doing a rally style cage in one is going to be tough. We did a pretty extensive cage in an M coupe a few years ago. Things like sill bars and FIA bars are going to be difficult to make and fit because of the shape of the interior jams. Make sure you tie into the rear diff mount as they tend to rip out. We replaced the entire rear with a custom mount that was tied directly into the cage.

  8. #8
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    So I'm seeing this flocking in more and more places now. How hard is it to do a nice job, and how durable would this be for daily driving? I really like the look, but don't want it looking all busted up and shitty in short order.

  9. #9
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    Quote Originally Posted by boostedinaz View Post
    Doing a rally style cage in one is going to be tough. We did a pretty extensive cage in an M coupe a few years ago. Things like sill bars and FIA bars are going to be difficult to make and fit because of the shape of the interior jams. Make sure you tie into the rear diff mount as they tend to rip out. We replaced the entire rear with a custom mount that was tied directly into the cage.
    Thank you for the tip. Car is getting the cage done next month. Do you know if the M coupe had halo race seats? One concern is getting the halo part of the seat inside the cage area without cutting into the transmission/exhaust tunnel. Seats in my car will be the OMP hte-r 400 that have the narrower halo.

  10. #10
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    Quote Originally Posted by boostedinaz View Post
    Doing a rally style cage in one is going to be tough. We did a pretty extensive cage in an M coupe a few years ago. Things like sill bars and FIA bars are going to be difficult to make and fit because of the shape of the interior jams. Make sure you tie into the rear diff mount as they tend to rip out. We replaced the entire rear with a custom mount that was tied directly into the cage.
    Thank you for the tip. Car is getting the cage done next month. Do you know if the M coupe had halo race seats? One concern is getting the halo part of the seat inside the cage area without cutting into the transmission/exhaust tunnel. Seats in my car will be the OMP hte-r 400 that have the narrower halo.

  11. #11
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    We have a flocked dash on the current rally car. It is pretty durable, but does not get as much use a a daily driver. I can take a picture if you want so you can see what it looks like after a coupe of years. Hardest thing for a DIY application is to get the material thick enough that you won't see dash/glue under the flock. Overall, it is very easy to apply, but only way to do it right is to remove the dash.

    - - - Updated - - -

    Thank you for the tip on the cage. Car is going to the shop to get the cage done next month. Do you know if the M coupe had halo race seats? Getting the halo part of the seat inside the cage area without cutting into the transmission/exhaust tunnel is going to be tight. Seats in my car will be the OMP hte-r 400 that have the narrower halo, so that should help some.
    Last edited by sebastianrally; 01-24-2017 at 08:50 PM.

  12. #12
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    Quote Originally Posted by sebastianrally View Post
    Thank you for the tip on the cage. Car is going to the shop to get the cage done next month. Do you know if the M coupe had halo race seats? Getting the halo part of the seat inside the cage area without cutting into the transmission/exhaust tunnel is going to be tight. Seats in my car will be the OMP hte-r 400 that have the narrower halo, so that should help some.
    I had a hard time getting my Sparco Ergo positioned inboard enough for my liking. The trick for me was to use the Planted seat brackets instead of the Sparco (or Momo, can't remember) brackets I had with my older seat. The Planted brackets are a straight L shape, whereas many others flare out at the bottom. Getting rid of the flare allowed me to get the seat another inch or so inboard and required no modification to the trans tunnel.

    I know the Z3 is a slightly different platform and likely tighter inside, but every little bit will help. There should be room to cut/pound on the trans tunnel if you absolutely have to, though.
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  13. #13
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    Quote Originally Posted by sebastianrally View Post
    Thank you for the tip. Car is getting the cage done next month. Do you know if the M coupe had halo race seats? One concern is getting the halo part of the seat inside the cage area without cutting into the transmission/exhaust tunnel. Seats in my car will be the OMP hte-r 400 that have the narrower halo.
    The car we built did not have a halo seat. Anything can be made to fit with enough work. I am pretty sure you could get a Halo seat in the car if it's narrow. Make sure you check the fitment with the windows rolled up as most rally sanctioning bodies require the cars to run windows up. In road racing it is usually the opposite with windows down being required.

    Here are a few pics of the cage I built in an S54 powered M coupe. This was a turn key build we did for a long time customer. He has 3 clownshoes all S54 powered.



  14. #14
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    Very nice! This weekend I towed the car from VA to Mass. for the cage build. Will post pictures when available.

    Suspension has been measured and ordered - it will be custom made, so will take about 6 weeks to ship from Europe. And the roof scoop came in for my birthday the other day:

    subir fotos


    Quote Originally Posted by boostedinaz View Post
    The car we built did not have a halo seat. Anything can be made to fit with enough work. I am pretty sure you could get a Halo seat in the car if it's narrow. Make sure you check the fitment with the windows rolled up as most rally sanctioning bodies require the cars to run windows up. In road racing it is usually the opposite with windows down being required.

    Here are a few pics of the cage I built in an S54 powered M coupe. This was a turn key build we did for a long time customer. He has 3 clownshoes all S54 powered.



  15. #15
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    Quote Originally Posted by sebastianrally View Post
    Very nice! This weekend I towed the car from VA to Mass. for the cage build.
    Is Chris Howard doing your cage? If so he just did mine and developed a great approach in doing so. I'd be happy to share what I did in the event you might want to put some of the ideas into use.

  16. #16
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    Quote Originally Posted by CMM3 View Post
    Is Chris Howard doing your cage? If so he just did mine and developed a great approach in doing so. I'd be happy to share what I did in the event you might want to put some of the ideas into use.
    It is Bill Doyle of Cagethis.com. The cage will be built to the NASARallySport specifications (which requires some specific things: https://www.nasarallysport.com/rules...Appendix-B.pdf). I have seen the pictures you posted on your build - it is looking great and has been an inspiration for some of the ideas I have (I specially like how you tied the cage to the floor to strengthen the rear subframe where the rear diff attaches). How are you mounting the seat(s) to give you enough room between the helmet and the top bar on the roof?

  17. #17
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    Quote Originally Posted by sebastianrally View Post
    It is Bill Doyle of Cagethis.com. The cage will be built to the NASARallySport specifications (which requires some specific things: https://www.nasarallysport.com/rules...Appendix-B.pdf). I have seen the pictures you posted on your build - it is looking great and has been an inspiration for some of the ideas I have (I specially like how you tied the cage to the floor to strengthen the rear subframe where the rear diff attaches). How are you mounting the seat(s) to give you enough room between the helmet and the top bar on the roof?
    Bill did the cage in my nephew's car and I considered using him to do mine. But after doing a lot of research and talking to both I came away with the belief that Chris has a better understanding of load effects and how to make a cage stronger and stiffer. I think Bill is more of just a welder who builds to print, while Chris is more of an engineer equally capable at welding. Chris will also build to meet any spec required and does. The NASA, SCCA, BMW racing and other are all very similar with only minor variations. I'm pretty sure NASA and BMW just copy the SCCA specs, since SCCA has been around the longest and all the Pro cars comply to their requirements. You may want to talk to Chris just to get a comparison. He is at 508-429-6717 tell him Dan with the BMW Z3 sent you. I'm not trying to sell anything but Chris is now very familiar with a Z3 and I know someone that had a cage done by Bill who wasn't all that happy with the results and had to redo a number of things.

    Keep in mind that Randy Forbes did the rear reinforcement on my car and I built the cage on top of this. Without the work he did I don't think that tying a cage into the floor alone would be all that effective as it wouldn't tie into the subframe were the diff mounts because there is a sheet metal "u" channel about 1.5" wide x 1.5" high that the diff mounts attach to and this is all held together with spot welds. It's what typically tears apart in these cars, you can see this from under the car. As part of doing the cage I would get a kit from Randy which converts the car to much stronger dual ear diff mount, and have it installed as well if you already haven't done so. Add the rogue diff cover for added strength. This is a known weak point and prone to failure on street driven z3's that don't see anywhere near the amount of stress that a track car does.

    I used VAC floor seat mounts combined with their side mounts and mounted the seats in the lowest slots. I'm 6' 1" and with a helmet on I just cleared when I had the stock sunroof and all the trim in. I replaced the roof panel with a non-sunroof version and with no headliner I now have plenty of room. The roof bars of the cage are behind and to the side so they don't come into play.
    Last edited by CMM3; 02-22-2017 at 09:36 AM.

  18. #18
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    Quote Originally Posted by CMM3 View Post
    Keep in mind that Randy Forbes did the rear reinforcement on my car and I built the cage on top of this. Without the work he did I don't think that tying a cage into the floor alone would be all that effective as it wouldn't tie into the subframe were the diff mounts because there is a sheet metal "u" channel about 1.5" wide x 1.5" high that the diff mounts attach to and this is all held together with spot welds. It's what typically tears apart in these cars, you can see this from under the car. As part of doing the cage I would get a kit from Randy which converts the car to much stronger dual ear diff mount, and have it installed as well if you already haven't done so. Add the rogue diff cover for added strength. This is a known weak point and prone to failure on street driven z3's that don't see anywhere near the amount of stress that a track car does.
    What exactly does his kit do to reinforce that mount? It looks like it is just some large tabs to the stock sheet metal.

    For the car we built the rear mount was already tearing out. We decided that in order to fix it once and for all we would get rid of the stock mounting and structure all together.

    We used a square tube to make a new mount and add in much more structure.


    Here is the underside almost done.


    Finished with the diff installed. I can guarantee this diff will never more again.

  19. #19
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    Quote Originally Posted by boostedinaz View Post
    What exactly does his kit do to reinforce that mount? It looks like it is just some large tabs to the stock sheet metal.

    For the car we built the rear mount was already tearing out. We decided that in order to fix it once and for all we would get rid of the stock mounting and structure all together.

    We used a square tube to make a new mount and add in much more structure.


    Here is the underside almost done.


    Finished with the diff installed. I can guarantee this diff will never more again.
    Randy's kit does does pretty much the same as what you've done in creating a boxed square tube for the diff to mount to. If you go to his site Sports Cars Plus or search the forums you'll see that it's much more involved than some tabs.

    The only thing different than what you did is that his kit converts the diff mount to a dual ear configuration using an e36 diff cover or the upgraded rogue engineering cover. You still have all the rotational torque being applied to a single mounting point which may be strong enough but it does't look like it would be that difficult for you to go to a dual ear configuration. The e36 or rogue cover bolts right onto the z3 diff so all you'd need to do is weld on the mounting tabs to your rectangular tube. I'm not sure how prone the single ear covers are to failure but they are made of cast aluminum and an ounce of prevention may be worth the effort:

    271Diff.jpg

    A few other suggestions.

    Since your building a track car I'd go with solid aluminum sub frame and diff mounting bushings. You can use the e36 version of the solid diff mounts from Turner and the sub-frame mounts are readily available.

    If those are rubber or even poly bushings in your trailing arm I'd replace them with Race hard Derlin available from Gargastic.

    The Derlin will squeak and these combined with the solid sub frame and diff bushing will introduce a lot of noise and vibration but this is a don't care for a track car and will prevent your rear suspension from moving around. Even the hardest poly bushings still deflect a great deal, heck I found even steel does as I had to move my front frame rails a bit to re-install the front sub and even with the cage and extensive reinforcements it wasn't all that hard to do. When the main suspension components move on the bushings all the desired alignments (camber, toe and in front caster) go out at the worst time under full load and you lose the mechanical grip.

    I think I see that you have the cam bolt style camber & toe adjusters. I had these in my car and they are a PITA since it's impossible to get the bolts tight enough to keep them from moving, it's a known problem as the kit is the same as used on the e30 and the only solution is to tack weld the concentric bolt. But then you can't adjust it any more. I had these removed in mine and went with the newer posi-lock style that Ireland sells. The only thing that you have to be careful about in using this version in the Z3 is that the plates are much longer and the vertical mounted camber plate will hit the gas tank so it has to be trimmed down by a 1/2 inch or so.

    Just my $.02
    You're build is Looking good.
    Last edited by CMM3; 02-23-2017 at 10:50 AM.

  20. #20
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    Curious what the status is on this.


    Also, what are you planning for suspension.

  21. #21
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    I was busy with work and with the car, so I neglected updates. I will post updates more frequently now as it will force me to make time to make small progress every day. So, here is a bunch of updates to bring it up to date...

    - - - Updated - - -

    Thank you for the tips. That is actually a different car - was just using as a sample for the reinforcement kit. Bill Doyle ended up doing a similar square tube reinforcement that is tied to the cage. We also went with the e36 diff cover to have two mounts. Thank you for the suggestions!

  22. #22
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    IMG_1577.JPG

    IMG_1578.JPG

    IMG_1576.JPG

    Cage is all done. Bill Doyle at cagethis did a great job. And best of all is that the halo seats will fit! Here are the pictures with one coat of paint.
    Last edited by sebastianrally; 07-11-2017 at 08:27 AM.

  23. #23
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    I will be using Reiger from the Netherlands for suspension.

    Quote Originally Posted by Whizbang Rally View Post
    Curious what the status is on this.


    Also, what are you planning for suspension.

  24. #24
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    IMG_1542.JPG

    IMG_1543.JPG

    Pictures of the suspension. Will not install it until after I reinforce the suspension towers, though.
    Last edited by sebastianrally; 07-11-2017 at 08:25 AM.

  25. #25
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    Next step was to put the dash back in. Will keep the vents functional so I can have air circulate while on transits between stages. Problem is that the new dash bar blocks some of the pipes for the vents. So I had to re-do the routing of some of them.


    IMG_1580.JPG


    IMG_1582.JPG
    Last edited by sebastianrally; 07-14-2017 at 01:46 PM.

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