M3 S54 exhaust manifolds for ZHP M54

[GoGators]

I found this flange on Ebay. I think it would work if I sliced it into 2 pieces in the middle. Might make the conversion a little simpler. I can weld it up no problem. Does anyone know if this will NOT fit the M54 exhaust ports? The ad says it will and they answered an email that said all M5x engines had the same dimensions for exhaust ports and bolts. http://www.ebay.com/itm/M50-s50-M54-...3D252079861500

the port spacing should be fine. prior to starting the project I found these, or similar on ebay. the company would make a SS version for $150. I chose to use the M54 set bc I got them for $40.

all you are really gaining is you don't have to cut the manifold off the flange, which only took ~15 minutes with a cutoff wheel and sawzall. however, its always nice to start with a fresh machined piece rather than ~10 yr heat cycled metal...

[GoGators]

looks legit... if the M3 headers minus the flanges fit in that flange, that would save you some work

the challenge is access for welding... the external side of the flange, for the forward header is extremely restricted. I don't think its impossible, but I would like to see how someone did it!!! this is why I chose to have the interior tig'ed. I put a fillet weld on the exterior where accessible primarily to improve strength.

so, either flange (new or used) I think you will have to die-grind out the bores to accept the tubes as a slip fit (to accommodate the interior weld).

[Sockethead]

Saw these on Vibrant Performance website Pretty pricey though:
http://vibrantperformance.com/catalo...1022_1124_1406

Mild Steel version:
http://vibrantperformance.com/catalo...1022_1124_1407

[GoGators]

Saw these on Vibrant Performance website Pretty pricey though:
http://vibrantperformance.com/catalo...1022_1124_1406

Mild Steel version:
http://vibrantperformance.com/catalo...1022_1124_1407

yea, about ~$100/ea on jegs. same problem still exists though, challenging external fillet weld. so if you plan to interior weld, like I did, you will have to immediately grind away a lot of the material on that $100 flange...

[Sockethead]

yea interior weld is the only way to get a seal on it

[terraphantm]

so far pretty darn good. I only have about 250 miles on them.

so far, only one SES, it came on after I sat in traffic at idle for ~30 minutes. it threw both Cat efficiency low codes. cleared them and they haven't come back.... I haven't had time to research it further, but I am using my 330i O2 sensors which are not the same as M3s. the precat sensor bungs I cut ~15mm off the bung so that the sensor would protrude into the pipe at the same depth as they did on the 330 manifolds. I did NOT cut the after cat bungs, though maybe I should have. not sure yet. if I were you, I would cut the after cat bungs, it seems likely that might be my issue. I need to research further, but if I continue to get those codes I may try M3 sensors, if I figure out that they will work.

I wonder if the M3 being a LEV car rather than ULEV makes a difference here. IIRC M3 cats are less dense than most of that vintage (200 CPI vs 400 CPI). Don't know if that's enough to throw off the readings.

You won't be able to use M3 pre-cat O2 sensors since the ZHP has wideband precat O2 sensors while the M3 uses narrowband.

[Aeternalis]

Saw these on Vibrant Performance website Pretty pricey though:
http://vibrantperformance.com/catalo...1022_1124_1406

Mild Steel version:
http://vibrantperformance.com/catalo...1022_1124_1407

Details say that the part number includes two flanges. So about $65 each; not too bad.

http://vibrantperformance.com/catalo...oducts_id=2719

[GoGators]

I wonder if the M3 being a LEV car rather than ULEV makes a difference here. IIRC M3 cats are less dense than most of that vintage (200 CPI vs 400 CPI). Don't know if that's enough to throw off the readings.

You won't be able to use M3 pre-cat O2 sensors since the ZHP has wideband precat O2 sensors while the M3 uses narrowband.

I need to put my fluke on the post cat sensors see what mV they are putting out. my OBDII reader will only read real time output of the pre-cat sensors. the SES has been coming on regularly now for the cat efficiency codes.

[terraphantm]

You should be able to get live readings with INPA. And Testo should be able to log them

[GoGators]

still trying to solve this problem without the necessary tools... I don't have INPA/NCS, heck I don't even own a laptop now (use ipad).

I bought a second hand M3 post-cat O2 sensor, cut and soldered the leads to a non-m3 post cat plug and tried it out. light came back on after several miles of driving, both banks (one running the M3 post-cat O2 sensor, the other running the non-m3 O2 sensor).

I am obviously more than a little surprised the M3 sensor didn't work. does anyone know if its possible that the threshold (in mV) that OBDII would flag would be different from a 330 to M3 (possibly attributed to the LEV/ULEV rating)???

I couldn't read the mV from the sensor readily bc of the plug, it has male ends on the sensor lead. I am going to use the non-M3 sensor that took the plug off and strip the wires and use the fluke to see what the output is... though, I am not sure what that data will tell me!