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Thread: M3 S54 exhaust manifolds for ZHP M54

  1. #1
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    M3 S54 exhaust manifolds for ZHP M54

    after you read the title your first thought/question is probably "why?" if your first thought/question isn't "why?" you probably have tried building for SCCA class STX.

    STX (all of street touring) per SCCA rules requires Cats to be within 6" of their OEM location. I have personally challenged this via SCCA's official channel for rules changes, rejected, no rationale provided by SCCA. Headers are STX legal, but must conform to the aforementioned Cat restriction. this (obviously) eliminates off the shelf headers for ZHPs. essentially, the cat rule makes german cars the only one that cannot run header in Street touring...

    I am getting real close to attempting to modify factory S54 exhaust manifolds to fit my M54. the cat locations are similar, the OEM manifold is tubular and though I have no way to compare the flow improvement, visually, it appears substantial. consider, they are designed for a 0.2 L larger engine spinning at ~1000 rpm higher = lots more air flow....

    i should note that i am attempting this bc cost is low. S54 manifolds go for less than $200. reproduction flange on ebay ~$100.

    plan would be to use either OEM or reproduction flange for M5X, cut off S54 flange from S54 manifolds, weld, then use M3 section1 tubing connection and reduce from 60mm to 50mm exhaust tube under the car...

    below are things I have considered... and some associated risks. if you can think of something I have missed, please post to this thread!!!

    -exhaust ports are round vs oval, based on reproduction flange available from kniseleyperformance, I think this will be a non-issue. note, per pictures on eatsleeptinker.com's spec E46 engine build, S52 manifolds fit M54. so the kniseley flange should mate fine.

    -bore spacing, according to the forum posts, bore space is 91 mm for M54 and S54. this makes some sense.. but hate to trust forum posts...

    -exhaust port angle, I have no way of knowing whether the angle of the ports on the head is same, but i think there is a chance to modify the angle by adjusting the S54 pipes where they will be welded to the flange..

    stud/bolt access, this could be an issue as the flange bolt patters are substantially different. i am hoping... there will be room to access the nuts/bolts... (hope is not a plan, but its all i got)

    -Cat space, i am assuming that if they fit an E46 M3 coupe, they should fit an E46 coupe/sedan..

    -section 1 pipe on M3 is 60mm. it 'appears' to run in the same location as E46 non-M3. hope to be able to simply reduce using a small section of 2.25" pipe..

    -O2 sensors, i don't see why this wont be plug and play.


    pertinent thoughts? educated concerns?

  2. #2
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    I think you'd have better luck with the E36 M3 engine (S52 or S50) headers...same improved design on basically an engine that is the M54...

    http://e46fanatics.com/forum/showthread.php?t=861866

    Current:
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  3. #3
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    Quote Originally Posted by NoVAphotog View Post
    I think you'd have better luck with the E36 M3 engine (S52 or S50) headers...same improved design on basically an engine that is the M54...

    http://e46fanatics.com/forum/showthread.php?t=861866
    I surely agree that would be easier, but it doesn't solve my primary problem. S52 cats are located under the car, several feet from the cat location in E46.

  4. #4
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    Since it will still have the cats will there really be much improvement? I guess you can weld in racing cats to increase hp.
    2004 Silver Grey ZHP Sedan 6 Speed Manual
    CDV Delete, AUX Input, Clear TMS Lights, Stealth Bulbs, Orion V2 Angel Eyes, Black Grille,
    aFe Stage 1 CAI Pro 5r, Dinan Front Strut Brace, CF Splitters, Active Autowerke Headers

  5. #5
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    Quote Originally Posted by NickZHP View Post
    Since it will still have the cats will there really be much improvement? I guess you can weld in racing cats to increase hp.
    there wont be a dramatic difference. 4-5% hopefully. M3 manifolds are tubular, far superior design to ours. I don't think installing high flow cats will be practical, but use of the M3's should still be an improvement since they were designed for higher flow rate.

    I will post a pic of 330 vs M3 manifolds when I pick up my donor set of 330 manifolds. found a set locally for $40. picked up an M3 manifold and section 1 pipe set for $150 this weekend.

  6. #6
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    Awesome, keep us updated on the project I'd like to hear how it goes. I recently finished installing my Active Autowerke headers and I definitely feel an increase in power and a nice improvement in sound. I can't be in STX anymore but I just do it for fun anyways so I'll gladly eat dust in Street Prepared
    2004 Silver Grey ZHP Sedan 6 Speed Manual
    CDV Delete, AUX Input, Clear TMS Lights, Stealth Bulbs, Orion V2 Angel Eyes, Black Grille,
    aFe Stage 1 CAI Pro 5r, Dinan Front Strut Brace, CF Splitters, Active Autowerke Headers

  7. #7
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    i now have a 325i manifold and an M3 header and sectioName:  IMG_2336.JPG
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Size:  556.0 KBn1. here are some comparison pics of the short manifolds.

  8. #8
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    Name:  IMG_2341.JPG
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Size:  530.2 KBName:  IMG_2342.JPG
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Size:  787.3 KBcomparison pics of the long manifolds

  9. #9
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    now having looked at the two (off the vehicles for the first time) a few things are apparent that I wasn't expected. neither the exhaust port flanges are welded on, they appear to be some sort of press fit (this might make disassembly easier for me). the 330 casting-like manifold is heavy. the O2 sensor bungs on the M3 exhaust are a lot long than the 325 manifold. i presume this would make the O2 sensor not go in as far, for the after cat sensor that seems fine. for the important O2 sensors, ones before the cat, this seems like it might present a problem. will do some research, but i am leaning towards shorting the bung so the sensor is more in the exhaust stream.
    Name:  IMG_2345.JPG
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  10. #10
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    i plan on starting to remove the flanges soon. i probably wont be able to put the car on jackstands and remove it from service for the week or so this will probably take anytime soon. hoping for May timeframe to start the fabrication process.

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