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Discussion Starter #1 (Edited)
After seeing some encouraging dyno results, I decided to convert my car from an M54 manifold to an M50. The engine already has a few performance improvements. It's an M54B30 rebuilt with a maximum factory overbore, a head decked the maximum allowable to increase compression, and ZHP cams. It's got a set of Technic V3 headers to a Burns 3" merge and a single Magnaflow muffler terminating just before the rear differential. The intake is a custom long-tube with the filter in the bumper and it is all controlled by an MS3 ECU running Bosch "green giant" injectors and an M50 mechanical throttle body. It puts down 230-235hp at the wheels and uses the factory DISA valve.

"But you'll lose the DISA!"

This is true. But the DISA valve only boosts torque below roughly 3800 RPM (we tested this extensively over more than 10 hours on the dyno) and it's a really small improvement - only 5-7 ft-lbs. The M50 manifold gains more than make up for that - it makes significantly more power from 4,000 to 7,000 RPM, where this engine spends its entire life.

M54 manifold removed



Everyone knows this, but the M50 has much larger runners. Wider by about 0.4" and taller by about .050"



First problem of many to come. The E46 fuel rail mounting feet interfere with the runners on the M50 manifold. If I had an early E46 return-style fuel system, I could use an E36 rail. But since I don't, I'll just cut the ears off of mine.



With the ears removed the injectors line up perfectly. Note the injectors need to be rotated 180 degrees so the electrical connection doesn't interfere either. You will want to use injectors with a symmetrical spray pattern like the Bosch 42lb ones shown here.



Here is a bracket and an aluminum spacer I fabbed up to mount the fuel rail to the manifold. 2018 edit: Since these pictures were taken I have made new, machined pieces that look a lot nicer. But this certainly worked well enough.



Here's the rail bolted up.



Because the injectors are rotated the factory injector wiring harness with its plastic organizer (which we use with the Megasquirt) won't fit. So each plug needs to come out of the organizer and get wrapped with tape.



I'll need to make a relocation bracket for the power steering reservoir as well. It won't fit in its stock location because it hits the plenum.



Here's a test fit of the manifold. So far so good, but lots of work yet to go, including removing the head for the port matching and figuring out where to hook up all of the necessary vacuum connections. And of course, re-tuning!

 

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Great. As soon as I get everything I need for my M54B30 conversion I hear that M50 is even better!!!! Very interested to see how this goes. Best of luck!
 

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Discussion Starter #3 (Edited)
No meaningful progress this week other than picking up a used head to do the port matching on and making one of the two porting templates needed out of some .063" sheet 6061 I had.

 

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Good luck!


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Discussion Starter #6
I can't post the other dyno data unfortunately, but I will certainly post my before and after when I get back down to my tuner.
 

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Discussion Starter #11
Shape looks similar to mine but my torque curve is flatter in the 4000 to 5000 window. Probably header related.


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interesting, looking forward to more on this. I did the m50 manifold conversion on my e36 which I'm assuming was way more simple. Also they have multiple "conversion kits" with small odd's and end's pieces so you have everything needed for install. Definitely the best performance mod on that car and never even got around to a tune for it. Good luck.
 

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Discussion Starter #15 (Edited)
Got the head off, port matched and back on the car. Pretty fun.







Next up, deleting the evap system, working out how to plumb in the ICV, CCV, fuel pressure reg and the brake booster.


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Can't wait.

I will say guys, the new N52 is a gem, power is effortless and smooth - plus there is some potential left on the table.
The downsides are that there isn't, and probably will never be any real aftermarket support due to the Turbo N54/N55.
 

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Discussion Starter #20 (Edited)
The DISA doesn't really do much once you've optimized the fuel/spark/VANOS (5-7 ft-lbs), and doesn't come into play at all in a race car since the RPM are over the useful band of the DISA 95% of the time. I can't remember the last time I saw less than 3,800 RPM in the data. No plans for FI, but who knows? If I do, the work I did will just make it easier.

If anyone is interested, I bought a spare head in case mine had any issues and I port-matched it for the M50 manifold. So if someone else wants to try this little experiment (not really an experiment since I already know what the result will be!), I'll sell that head. Just PM me and we can work something out.
 
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