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Thread: RHD Individual Throttle Bodies on my S52 M Coupe

  1. #1
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    RHD Individual Throttle Bodies on my S52 M Coupe

    Alright folks. I did it. It's amazing. More photos can be seen here, https://photos.hayespotter.com/#15496440759000 .


    01258c726519bef1ad86a563bd3140b8.jpg
    ab2cc85cbc386e0821a5595d75fe5cfe.jpg
    96bd13f8532c7451b9bf0661d2095093.jpg
    oil catch can and dipstick mounted on a custom bracket underneath the plenum.
    de49bea762e88be835037e2ed85a4888.jpg
    542a62f872dbe631b2b9ce7974ccc3da.jpg


    This is the RHD M50/52 ITB kit, http://racehead.com.au/products-page...50-52-itb-kit/ , installed on a stock internals S52 in my M Coupe currently using a base RK tune with the factory DME and MAF, idle controlled by stock ICV. I wanted to do something a bit different so here we are. The cost to horsepower ratio is not great, but I didn't do this for raw power. I couldn't give two shits if you think I should have gone forced induction or swapped in a s54.

    Install is fairly straight forward but much more tedious if you intend on using the stock DME with the MAF. Overall I do not recommend doing this, if you're on an OBDI motor you should really just run an aftermarket ECU from the start. The hardest part of the install is retaining everything needed for stock operation along with sealing everything properly. In order to get everything to seal up well I had to make a custom gasket to seat between the carbon fiber plenum and backing plate, and then lined with silicone. All screws in the TB's and backing plate are threaded with teflon tape just to be safe. It is very important to follow RHD's instructions and to sync the throttles accurately. If one set of throttles doesn't close all the way it will keep the other 4 throttles from fully closing as well.

    The silicone coupler on the end of the plenum is 3.25 inches down to 3 inches for the stock MAF. There really isn't any room in the z3 for a proper air filter so for now I'm using a custom application pancake filter from K&N, it's alright for now, there is room for a cone filter in an e36. I am planning on going alpha-n, at which point I'll fit a proper cone filter since I can then remove the MAF. Another small nuance for Z3 owners is that the throttle position sensor will not fit on the back throttles because of the heater control valve, I opted to just bend the HCV out of the way. I also had to bend the oil dip stick out of the way, and this is now mounted on a custom bracket with the oil catch can.

    Cruise control and traction control are obviously deleted, along with stock oil separator. Three now unused cables are not ziptied off to the side, the third plug hanging out in my engine bay I honestly do not remember where it goes. The oil separator is replaced with an oil catch can from Turner Motorsport, hooked into the vacuum block for the ITB's. I re-used some of the fittings from the stock oil separator lines for this. The intake air temperature sensor and idle control valve are both plumbed into the aluminum backing plate, pulling air directly inside the plenum. The IAT sensor is kinda jerry rigged; RHD provided a properly sized fitting for the ICV.

    Anyone who has heard about these throttles has probably heard that the throttle bearings leak air. This is true. They are designed to seat properly and seal when warm and properly bedded in. I've put about 250 miles on the throttles so far and they perform very well when warm, but are very sticky when cold. They are slowly getting better on cold starts the more I drive it. Idle is pretty good when warm, but sometimes inconsistent. I believe the ICV is really unsure about itself. Sometimes when I come to a stop the car will drop to ~650rpm and be rock steady, sometimes it'll drop to ~1100 or ~1000 and stay there until I blip the throttle and then it will return to normal idle speed, sometimes it will hang around 1000 rpm and then figure itself out. The car has not been tuned properly, I am still on a base RK tune designed for a stock S52, and again, I'm planning on going alpha-n in the near future.

    Now on to the fun stuff.

    The car sounds absolutely amazing. It revs quickly and smoothly and is overall an orgasmic experience. I have not noticed any torque loss in the low range, but it is a bit less punchy in the mid range. Above 4000 RPM the car starts to pull harder and sounds really really good. Above 5500rpm it absolutely screams and just gets better through to the redline. The pull is incredible. I plan on going alpha-n, modest cams, and turner shorty headers to compliment the ITB's.

    This post is a little all over the place and I'm sure I missed some things so please feel free to ask me any questions you may have.







    Last edited by blindrooster; 02-09-2019 at 04:40 PM.

  2. #2
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    Looks like a fun project. Will be interesting to see your solution to the filter.

  3. #3
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    Gotta be honest, didnt seem to respond much faster than original in that third video

    Ive always been interested in these but tbh dont see much advantage or benefits over stock

    Shouldnt you also do long tube headers to accent the high-RPM power you were praising with these? Shortys will help with torque but choke it a bit up top which is where you were praising the itb's

  4. #4
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    Quote Originally Posted by BimmerBreaker View Post
    Gotta be honest, didnt seem to respond much faster than original in that third video

    Ive always been interested in these but tbh dont see much advantage or benefits over stock

    Shouldnt you also do long tube headers to accent the high-RPM power you were praising with these? Shortys will help with torque but choke it a bit up top which is where you were praising the itb's
    Third video really doesn't do it justice, looking back at it a bit closer I see I still have the adjustment screw for the pedal set somewhat light, I'm running it tighter at the moment.

    You are absolutely right, long tube is what I want, not shorty's.

    On the stock tune it definitely performs better than stock (minus that mid range torque). I'll be posting before and after dyno results, especially when I go alpha-n, however I might end up leaving it somewhat modest to retain some more torque in the low and mid range. I'll see I guess, haven't fully decided.

    All that said, if you are looking for more power, I really do not recommend going this route.

  5. #5
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    Iím full bolt ons + cams and I would assume these would complement a build like mine over a stock motor but itís still sweet to have ITBs!

    Well done!
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  6. #6
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    Quote Originally Posted by BimmerBreaker View Post
    Gotta be honest, didnt seem to respond much faster than original in that third video

    Ive always been interested in these but tbh dont see much advantage or benefits over stock

    Shouldnt you also do long tube headers to accent the high-RPM power you were praising with these? Shortys will help with torque but choke it a bit up top which is where you were praising the itb's
    I don't see how a video is going to convey throttle response. I guess if the camera also showed the gas pedal?

    How quickly the engine revs is more dependent on the flywheel weight. Once the throttle body(s) is wide open, ITBs aren't going to make the engine rev noticeably quicker than stock. It's the transition from closed to open where the difference is felt, and a video can't really capture that.

  7. #7
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    Quote Originally Posted by earthwormjim View Post
    I don't see how a video is going to convey throttle response. I guess if the camera also showed the gas pedal?

    How quickly the engine revs is more dependent on the flywheel weight. Once the throttle body(s) is wide open, ITBs aren't going to make the engine rev noticeably quicker than stock. It's the transition from closed to open where the difference is felt, and a video can't really capture that.
    He is manually controlling the throttle cable in the engine bay. It conveys throttle response because there is a noticeable delay between when the cable is pulled to open the throttles and the engine making sound to indicate it has responded.

    ITBs are designed to help with throttle response by moving the throttle plate closer to the cylinder. These unfortunately have the throttle only moderately closer than the stock single throttle setup. A lightweight flywheel helps an engine rev, ITBs help with throttle response. I never said anything about how it revs or anything in my post though. Just how it responds

  8. #8
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    Quote Originally Posted by blindrooster View Post
    Third video really doesn't do it justice, looking back at it a bit closer I see I still have the adjustment screw for the pedal set somewhat light, I'm running it tighter at the moment.

    You are absolutely right, long tube is what I want, not shorty's.

    On the stock tune it definitely performs better than stock (minus that mid range torque). I'll be posting before and after dyno results, especially when I go alpha-n, however I might end up leaving it somewhat modest to retain some more torque in the low and mid range. I'll see I guess, haven't fully decided.

    All that said, if you are looking for more power, I really do not recommend going this route.
    Thank you for posting this!

    I'm planning on doing this someday. I've got an Escalade and am familiar with the LS, and would go that route if I was just looking for power. But I want to finish all the normal bolt-ons and build my car to be as much as it can be. I don't race competitively - this is my DD - I just want to build it and see what I can do with it while keeping its core an S52. (and yes, part of that is avoiding an S54 and its various maintenance headaches).

    I know these are new for you and I've read through the installation instructions from RHD and didn't see anything about it, but are you foreseeing any maintenance headaches with this going forward?

    Also, I don't see why they delete the cruise cable. Is there a reason for that?

  9. #9
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    Unrelated (brilliant work, by the way) but what exhaust setup are you running?

  10. #10
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    clean install man, its not a bad option to keep the MAF

    looks like you need more return spring as the idle gets hung up a bit when you release the throttle

    interested in seeing before and after dynos as there aren't many around for M5x/S5x platform
    Last edited by digger; 02-11-2019 at 02:33 AM.
    BMW E30 325is M20B33 in the making....... ITB's, roller rockers and stroked to the hilt

  11. #11
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    Quote Originally Posted by Cos270 View Post
    Unrelated (brilliant work, by the way) but what exhaust setup are you running?
    Stromung axle back with custom resonators, but stock resonators are still in place, so: stock res > custom res's (one before each muffler) > stromung mufflers .

    - - - Updated - - -

    Quote Originally Posted by digger View Post
    clean install man, its not a bad option to keep the MAF

    looks like you need more return spring as the idle gets hung up a bit when you release the throttle

    interested in seeing before and after dynos as there aren't many around for M5x/S5x platform
    Yep, this is what I mean by sticky when cold. It improves dramatically when warmed up, I've been keeping the return spring fairly tight.

    I'll post dyno's once it's properly tuned.

    - - - Updated - - -

    Quote Originally Posted by BimmerBreaker View Post
    He is manually controlling the throttle cable in the engine bay. It conveys throttle response because there is a noticeable delay between when the cable is pulled to open the throttles and the engine making sound to indicate it has responded.

    ITBs are designed to help with throttle response by moving the throttle plate closer to the cylinder. These unfortunately have the throttle only moderately closer than the stock single throttle setup. A lightweight flywheel helps an engine rev, ITBs help with throttle response. I never said anything about how it revs or anything in my post though. Just how it responds
    The reason the throttles aren't smashed up against the engine is so it doesn't lose all of it's torque. It's still closer than stock, and absolutely has a much quicker throttle response. Good compromise for me, I'm happy with it.

  12. #12
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    Any thoughts on why they ditch cruise? Do they just assume no one will be using this on a street car? I can't see a technical reason why they'd need to delete it.

    -Josh
    1998 M3/4/5 with most of the easy stuff and most of the hard stuff. 240k and feeling the heat.

  13. #13
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    Quote Originally Posted by blindrooster View Post
    The reason the throttles aren't smashed up against the engine is so it doesn't lose all of it's torque. It's still closer than stock, and absolutely has a much quicker throttle response. Good compromise for me, I'm happy with it.
    Wouldnt runners in the intake (like the s54, euro s50, etc) in front of the TBs allow the torque to be maintained while allowing the TB to be closer to the cylinder for faster response?

    Just sayin

  14. #14
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    The throttles closer to the engine doesn't change torque only throttle response for the simple reason at WOT it's like the throttles aren't even there

    The issues with closer are:
    - round to oval transition gets worse
    - throttles need to get smaller to maintain the same taper and shaft blockage is higher on smaller sizes
    - space for linkages etc can become more difficult
    BMW E30 325is M20B33 in the making....... ITB's, roller rockers and stroked to the hilt

  15. #15
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    Quote Originally Posted by digger View Post
    The throttles closer to the engine doesn't change torque only throttle response for the simple reason at WOT it's like the throttles aren't even there

    The issues with closer are:
    - round to oval transition gets worse
    - throttles need to get smaller to maintain the same taper and shaft blockage is higher on smaller sizes
    - space for linkages etc can become more difficult
    Good info. I was thinking part of it might be for space concerns for install and whatnot.

    - - - Updated - - -

    Quote Originally Posted by blckstrm View Post
    Any thoughts on why they ditch cruise? Do they just assume no one will be using this on a street car? I can't see a technical reason why they'd need to delete it.
    I'm not 100% sure but I wouldn't think it would be compatible with the new throttle linkage at all.

  16. #16
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    You could possibly duplicate the linkage for cruise but would require some extra brackets custom made
    BMW E30 325is M20B33 in the making....... ITB's, roller rockers and stroked to the hilt

  17. #17
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  18. #18
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    Still waiting for a full WOT pull to redline. I bet she sounds nice.
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  19. #19
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    When did you order these? I always see that they're out of stock on the website.

    I too intend on wasting money on my S52.

  20. #20
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    Quote Originally Posted by langley View Post
    When did you order these? I always see that they're out of stock on the website.

    I too intend on wasting money on my S52.
    I got them in may 2018, the company emailed me directly to let me know they were in stock and I hopped on it.

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