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M50 Manifold On M52b25 Engine


First I had to find a good M50 manifold and modify it "M50 manifold and modification to M52"  & "M50, manifold modification 2" so all the pluming would work as intended. I also had to make some minor modifications to the power steering reservoir and fuel rail bracket, no big deal.


Sins writing this in 2015 I have exchanged the fuel injectors to 116,87% larger injectors, new larger camshafts, oil cooler, refurbished the vanos seals, renewed all 24 valve stem seals, 6 new coils, modified the cold air intake, bypassed/disconnected the throttle body heat, new and larger viscose fan and coupling for hotter climate, 2 upper oxygen sensors and remapped all the fuel maps, vanos maps, timing maps amongst some other maps in the ECU. The result was a better fuel economy and better emission numbers, more power and responsive engine and cleaner exhaust without a trace of oil or any black soot on the end pipes, all this was done in 2019 to 2021 and going onward with fine tuning of the ECU.


Now that everything is taken apart it is a good opportunity to replace old and brittle plastic and rubber parts like the oil housing rubber gasket that usually is hard to get to.

Obviously there will be some loss of torque with this modification under 3500rpm. but after that, there is a lot of gain in your smile :D .


Unless your daily driving is mostly on long steep roads for longer time, then I highly recommend this rather simple conversion ;) .


The only way to compensate for the loss of torque is replacing both of the standard camshafts that came with the M52b25/30 with two new/used ones; intake  cam from M54b30 for the intake and another INTAKE cam from M50NV for the EXHAUST sound crazy but that is the rout to go. You have to perform minor modifications on both of the replacement cams.  (you can read more about the camshafts with other pictures, there is a rabbit hole, you should be aware of when buying a M54B30 camshafts, that you might fall into) more info. with; "Hotter Camshafts = More Power"


After having made this conversion I found out, that I have kind of, maxed out my fuel injectors A/F, they where the green Bosch (0 280 150 415) capable of around 124,32g/min,  therefore I have replace them with bigger "Bosch  0 280 155 830" (blue-grayish) these are newer type EV- 6 injectors without an interchangeable pintle cap. The 0 280 155 830 injectors are capable of 269,61 g/min, or 116,87,% higher  fuel delivery capacity than the original small ones that I previously used from the start. It goes without saying that remapping the ECU is mandatory sins the 830´s have the capability of much more fuel delivery from the get-go. Consequently I have rewritten all maps related to fuel and vanos accordingly. This is where "MS41 Quickflash", "RomRaider", "MLV"  and MS Excel come into play, to remap the ECU. You can read more about the new injectors hear;  116% Larger Fuel Injectors



The final message is; do not change to higher capacity fuel injectors in hope of getting more horses out of the engine, it does not work that way, it only drowns the horses you had, to much fuel does not teach them to swim:huh:, instead of running.  In most cases the standard injectors that came with the engine are cable of delivering more than enough fuel, despite some minor tuning.


Larger capacity injectors apply if you are going for a turbo or compressor or as in my case, larger cams, m50 intake manifold and headers with free flow exhaust and a rather small injectors to start with, capable of only 124,32g/min, and still, they might have worked out, but they where the older type of injectors and worn out, beside I wanted to have more buffer on the tuning if I would install a compressor or turbo.



I say again; If you are going to do this modifications; I would recommend, that the ECU should be remapped/tuned by someone who knows what he or she is doing to get the most out of  this modifications and with new larger fuel injectors you HAVE to remap the ECU, there is no way around it. 



You can just let it be as is, with the standard tuned ECU with only the M50 manifold swap and the current fuel injectors and you will get some adaptation up to a certain point from the ECU, but not the full benefits as by remapping of the ECU accordingly, to the new larger intake manifold.



All I need now is a COMPRESSOR ;)








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My 523i Conversions and Maintenance

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