Replacing M52 exhaust manifolds with S52

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  1. Replacing M52 exhaust manifolds with S52 
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    I've posted a couple of times about this and I've done a lot of searching. Most of the posts seem to quote from the same article that makes removing the old manifolds sound very easy. I thought I'd post how I got on and what problems i'm facing for anyone else that wants to try this.

    My car is a 1998 323i coupe with aircon - there is no secondary air pump etc attached to the manifolds on this model. I've already removed the backbox and center section which was fairly straight forward so I'll skip this part.

    Today I removed the M52 manifolds. Cracking the nuts off was the easy part, soaked them in penetrant and set about them with an 11mm flat edge socket. I worked from above and removed the front bank nuts first. All of the studs came out with the nuts. For what its worth, I was able to do this without the use of flexy joints etc, only straight sockets were used, despite having the flexy's available, I found them more of a hinderance than a help.

    Once the nuts were off however, I was unable to withdraw the manifold due to space within the bay - the connecting arm to the steering rack being the main culprit. I then removed the rear bank nuts, again, 11 of the 12 studs came with the nuts, the rear manifold was easy to remove once freed from the cylinder head.

    Then came the most frustrating part of the day, all the nuts were off, both manifolds were separated from the head, but I found it VERY difficult to remove the longer front bank from its bavarian prison. In the end, I removed the o2 sensor with the manifold in position and withdrew the manifold from the topside by squeezing it past the aircon pipes.

    Here you can see the old manifolds on the right and the M3 evo manifolds on the left.



    Now, my questions are as follows..

    How in the name of all the is holy are these going to fit back in? They appear longer and wider than the standard manifolds that were a tight squeeze in the engine bay.

    Will I have to remove the connecting arm from the steering rack? Doing so should give me a lot more room to manouvre. - It looks like it is secured with 13mm nuts with knuckles at both the steering wheel end and the rack end? Simple as that?











    With regards to the exhaust itself, the M3 exhaust is considerably heavier duty in every respect than the standard m52 system. I will weigh them for comparison, but the backbox alone must weigh double that of the 323 box.

    Thoughts please.
    Last edited by Mark_F; 16-07-2011 at 21:19.
     
     

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    Interesting mod this, as I have seen some of these manifolds up for sale. I will keep an eye on this one to see how you get on.
     
     

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    I`m hoping to do just the rear manifold on mine. Do you think access is ok with the front one left in?
     
     

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    Quote Originally Posted by sa utah View Post
    I`m hoping to do just the rear manifold on mine. Do you think access is ok with the front one left in?
    I'm not sure. You should be able to reach all 12 nuts from the top with the other manifold still in place, but I don't know if you will have the space to remove it from the bay with the front bank still in place.

    I'd say probably, but can't be 100% on this.
     
     

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    The weight comparison is as follows.

    Manifolds x2

    M52: 5kg
    S52: 6.9kg

    Center section

    M52: 13.5kg
    S52: 19.6kg

    Backbox

    323i single pipe: 13.6kg
    Evo Staggered twin: 22kg

    Total weights
    323i system 32.1kg
    Evo system 48.5kg


    I've also added more pictures to my first post of the rack position etc in relation to the cylinder head. It looks as though the rear bank will snake around the rack, but I have no doubt the rack connecting arm must come out for the mani to go in.
     
     

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    Interesting difference on the weight of the exhaust. I guess the 328 unit would be somewhere in the middle weight wise....

    Back to the manifold for a second, do you need to use any sort of gasket / sealing paste or does it just require the metal gasket?
     
     

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    My S50 is on a pallet on the garage floor, I removed the manifold and it was a right bitch to get to all the nuts, I wouldn't want to do it with the engine in the car

    Good lick with bolting it back up
     
     

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    Interesting write up. Having looked into this myself I discovered that not only was the M3 system much heavier there was no power gain to be had and there is a thread on another forum showing a dyno print before and after with a power loss. Hats off to you to what you're doing but you may want to change it back. See how it goes though.
     
     

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    Quote Originally Posted by gringog60 View Post
    Interesting write up. Having looked into this myself I discovered that not only was the M3 system much heavier there was no power gain to be had and there is a thread on another forum showing a dyno print before and after with a power loss. Hats off to you to what you're doing but you may want to change it back. See how it goes though.
    If there was no performance difference, and possibly a power loss don't you think BMW would just have slapped some 323i manifolds on the M3 and saved a lot of money.
    M3 manifolds are equal lengths on the pipework which is important for making more power, the hashed together standard 323i pipes will never be as good as the M3 manifolds.
    The difference when fitted to your 323i may not be noticable when done but with other mods like a M50 inlet manifold a big bore throttle body, cams and a chip it would make a big difference.
    Good luck with it
     
     

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    Quote Originally Posted by plumb View Post
    If there was no performance difference, and possibly a power loss don't you think BMW would just have slapped some 323i manifolds on the M3 and saved a lot of money.
    M3 manifolds are equal lengths on the pipework which is important for making more power, the hashed together standard 323i pipes will never be as good as the M3 manifolds.
    The difference when fitted to your 323i may not be noticable when done but with other mods like a M50 inlet manifold a big bore throttle body, cams and a chip it would make a big difference.
    Good luck with it
    Totally agree Plumb to a point but thats not what the Dyno plots show that I saw. Add to this the considerably heavier system and all the ball ache to fit it you have to ask is it worth it?

    I'll see if I can find the thread with the Dyno plots.
     
     

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