RomRaider

Conversion is still not done but I will keep updating the topic. I decided to learn ECU tuning and did a research on MS40 tuning. Decided to convert my e34 to MS41 after I saw what I have to buy and how many times I would need to replace chips on MS40. Started off with deciding whether to change the whole installation or re-pin the ECU. Saw that people had many issues with re-pinning the ECU and since I had a stock M52B20 installation I decided to change it. When changing the installation you need to have electrical knowledge (my father #veskobx helped out a lot). As a lot of people have written already it is best to switch to VDO m52 sensors everywhere( sensor situation is bit more complex I will describe later in post). E36's have a difference in the main power cable that goes to the battery( there isn't a terminal on the end of the power cable) ,so I put the cable from e34 which has a terminal on it just as it was connected before from starter to battery.
Give attention to the plugs because with the m50 and depending on what year it is you might not have an AC and of course a VANOS so two plugs wouldn't be connected. Follow the wiring diagram even if the plugs connect smoothly (have the proper grooves). Knock sensors could be easily installed as well. They sit where they normally sit on M52 engines you just need two bolts-there is already a thread on the engine itself. For the MAF sensor you could keep the same box, throttle body and hose, just change the MAF itself. Charcoal canister (plug is on the same splice as the MAF) seems to be giving me issues(working constantly when plugged) but I will remove it either way. Crank sensor from M50 wouldn't work because a hall sensor from m52 is needed. Camshaft sensor is the same on both engines but the trigger wheel on M50 is different(this is a mechanical part on the camshaft itself. It is used by the sensor to determine camshaft position). To solve this you would need to put M52 trigger wheel. Decided to put an M52 camshaft with the cam tunnel but there is a difference in the lifters (M50 has 35mm lifters vs M52 33mm lifters diameter). This is because M50 has two springs on one valve and the lifter needs to be wider for the spring to go in it. Keeping the M50 tunnel you have to remove some material from it where the M52 camshaft touches it(If you spin the cam you will see where it gets stuck it is not too big of an issue). Everything else seems to be with the same dimension. Also checking you PACMAN plug that's on the drivers side in the engine would be best but with mine there was no need for rewiring. When I first tried doing a diagnostic the OBD2 which I installed temporarily didn't work. It was an issue with how it was grounded. Afterwards it was all fine and then I saw the cam sensor was getting 59 degrees because of the wrong trigger wheel.




After some time and hassle car is running properly. When putting the M52 camshaft you should choose a way to make the trigger wheel not spin as we don't have a vanos anymore. I choose to pyt another pressure plate on it(the thin one). Works perfect. After putting everything together the car still didn't start. There was a difference in the crankshaft plate(from where the crank sensor gets readings). This is easily fixed by drilling a hole about 120 degrees to the right from the existing one for the pin(look for alignment online on M52 and you will manage with drilling the new hole). When the crank plate was put in the proper way the sensor could finally get proper readings and car started normally. Revved higher without any issues.

All of this was thanks to the knowledge and passion of my father @veskobx!!!