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My 8HP45 gearbox conversion with Maxxecu

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    My 8HP45 gearbox conversion with Maxxecu

    I thought I start a thread. I Couldnt find much hit when I searched and I just wanted to share my story.
    Internet forums disappearing thanks to social groups which are rather chaotic & disorganized and nearly impossible to search within... I found R3vlimited is one of the last stand where I was able to source answers to many of my questions throught my build.
    I had a BMW E21 when I was 20. I just loved it and I thought I build my dream car out of it one time. Im 44 now... The car was moved to several locations, stored when 2 years ago I decided to take on this build. I had several E30s in the past but I never understood the hype around them. It is just not my thing. So after 24 years Im about to finish my project which is:

    M20B27 turbo, fully forged engine. 24td crank, chinese H-beam rods, and JE forged pistons. 8.5 ETA compression ratio. 885 head, Z45 turbo cam, PULSAR PSR 5455G aka G30-660 0.70A/R. E36 M3 EVO LSD and tons of mods.
    I bought a VEMS 15 years ago but things evolved and I realized it doesnt offer what I need. I sold it and bought a Maxecu Race. When I bought Maxxecu my gearbox was a 6 speed manual on my M20 off E46 320d, GS6-37DZ.
    Maxxecu was in the development (still is) of the 8HP gearbox control added as an additional feature (FREE!) to their Mtune software (still beta). 8HP gearboxes came on many many vehicles, Jags, BMW, Audi, Porsche, Dodge and they have many variants.
    Then I decided I change my project again and fit a 8HP45 off an N55 (same gearbox is on N52). Starter location is the same as on M20, M50 and has the same bolt pattern that requires NO adapter plate at an extra cost.
    Unfortunately M20 engines are slant in 20 deg whereas other newer engines 30 degs. I decided to cut the bell housing and weld it. Wasn't easy as it seemed like AlMg alloy which is not as easy to weld as AlSi.
    I used the 8 bolt pattern automatic flywheel off N54, part number 7553157. They become rare on Ebay as everyone wants them for their 8 bolt PCD. Newer cranks have 6 bolt pattern.

    My Instagram account is here with videos and pics: https://www.instagram.com/bmwe21turbo/

    I made a huge mistake and after cutting up the bellhousing I clocked the gearbox at 20 deg. This has proven to be a huge mistake as M20 engines do not sit exactly at 20 degre. They are about 18.5 degs and I did not measure it. I just relied on the 20 deg info.
    When we mounted the new tranny I realized that it will not sit in the right angle so we had to play a lot with various engine mounts to turn the engine to the correct position. The proof is in the pudding. Lessons learned.
    After removing old pilot bearing from the end of the crank the automatic torque converter slides straight inside the old M20 (M21) crank.

    What I needed for this conversion:

    * F10 LHD selector: 9296904 (confirmed, working with Maxxecu)
    * Brake pedal switch
    * Maxxecu
    * Starter adaptor ordered from here: https://shop.zedperformance.co.uk/8H...tarter-adapter
    * Custom propshaft
    * N54, 8 bolt flywheel
    * Maxxecu 8HP harness (you can build you own if you want)
    * Custom made 8HP oil cooler. I used a 1.9 TDI fuel cooler. Part number 1K0203491A, mounted under the car.
    * Other mods. You will certainly need fabricating skills.

    What you DONT need:

    * Turbolamik
    * CanTCU
    * In some instances Gearbox-Engine adaptor plate

    I know... many says that going to automatic is a mistake. I Dont see this way. 8HP can be driven in manual mode too and much more fun to drive. They are cheaper and provide smoother gear change than expensive DCT gearboxes. Maxxecu currently controls 8HP45 and 8HP70 gearboxes by flashing a firmware onto them. You can either rent a flashing tool and do it on your own or you can buy already flashed 8HP TCU control unit.

    You don't need to cut & weld anything if u want to mount this gearbox onto M50, M52, M54... they will just fit straight on... you only need to enlarge 2 of the top bolt holes on the gearbox just like I did.
    I plan to hit the Dyno with 20 psi in the next month. Currently Im waiting for the new cooler and charge cooler.

    I want to say a big thanks to Revlimited througout my build. Plenty of advices from experienced users.

    #2
    This is a very interesting project. How much driving have you done on the new setup?
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

    Comment


      #3
      Super cool. I have been sort of following the 8hp conversions and the go to was those standalone controllers. but as you say the max ecu i think are one of the first with a built in controller,

      super cool project. how was the tuning side of it? i have no understanding of tuning the auto, was it fairly straight forward? does it integrate the auto control well with the engine control? any cool tuning strategies you've implemented between the engine and the auto? Ill have to read the maxecu manual.

      Huge bummer on the 20deg vs 18.5. my trust in internet information was lost long ago.


      Comment


        #4


        made me want to put one in the E39 wagon.

        Haven't yet, but I HAVE gotten over the need for DSG- a fully programmable 8HP sounds like more fun with less... clunk.

        t
        now, sometimes I just mess with people. It's more entertaining that way. george graves

        Comment


          #5
          I didint get notified about the replies... I was'nt able to drive a lot as I still have cooling problems and Ive got no valid MOT. I ordered a custom made larger alu radiator for the engine and a charge cooler but not fitted yet. I was just driving the car in my street up and down but it feels real good. It is just so strange that this old engine mated to a much newer 8HP gearbox and these two work just fine. There are settings in Maxxecu that can be changed eg. at what RPM the gear switching have to happen or line pressure. Maxxecu offers 4 settings for the 8HP gearboxes. STREET, SPORT, TRACK and DRAG with less and less slip allowed.
          Once the TCU is flashed, harness connected to Maxxecu the ECU recognize the gearbox and selector straight. I had a small issue when Maxxecu complained that it cannot communicate with the TCU but then I just had to swap the cambus wires. Otherwise only 5 wires required to be connected to the ECU.

          * Rock solid chassis GND
          * 12+
          * 2x canbus for communication
          * Wake up 12+ from Maxxecu to 8hp.

          My old car doesnt have an ABS yet just a OE rear break prop valve. That ensures that the rear wheels will never lock up. So when I first tried then car was raised and no matter how hard I pressed the brake pedal it wasnt able to stop the rear axle from turning in D or R mode. I managed to do it only in STREET mode where the most slip is allowed. Now I installed an adjustable prop valve to be able to add more brake force to the rear axle. Otherwise its not fun to stop on the dirt road. This is kinda normal when you got an engine with high RPM. Mine is 1600 cold, 1100 when warm and this gives a higher line pressure thanks to my turbo cam.

          Turbolamik has a "clutch sleep" feature for this problem. When engine is idling and brake switch active then it disengages 2B clutch. Explained here:



          I brought this problem to Maxxecu support and they said that at the moment they cannot control the solenoids & clutches. I hope this later on will improve but I already ordered an MK60E5 ABS and plan to retrofit it. That should solve my problem.
          More and more Maxxecu users convert to 8HP with Maxxecu and all of them so far very happy for the swap. Some users changed DCT to 8HP and they said they didin't regret the swap. Driveability improved in town over DCT.

          If someone decides to take on this swap it is often a problem which TCU can be flashed with Maxxecu firmware. Not all controlers are compatible but I heard that this zedperformance.co.uk website also sells pre-flashed controllers with or without exchange. It can be handy when you find a suitable 8HP70 gearbox but you dont know what the TCU number inside. Then it can be quite unpleasant suprise when you open the gearbox and find out the TCU chip number is not compatible with Maxxecu. Mine luckily was compatible so one Maxxecu dealer managed to flash mine with Maxxecu's firmware. In case you are out of luck it might be a good idea to contact that company I mentioned.

          Some users also reported 10% power loss. They had Dyno before with manual and after with 8HP fitted. Maxxecu support is great and they helped me out with most of my problems.
          Last edited by E21M20B27; 10-26-2024, 08:29 AM.

          Comment


            #6
            I would not have considered that brake issue but it does make sense. It is an auto afterall, so it will try and creep.

            Can you setup a separate output from the ecu to disengage 2b clutch? you'd have to make sure the car is stationary, or under X km/h and the brake is on I guess. or handbrake switch? id have to think about that...

            Sounds like a fun but challenging project.

            Comment


              #7
              Good project!

              I have a Gen2 ZF8HP50 behind a 2.8l M50 turbo in my E30 and what a ripper of a trans it is! The shifts are <0.3 seconds under WOT and having paddles shifters makes it even more fun.
              -----------------
              89 M50B28 turbo
              LINKY
              -----------------

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