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Thread: E30 Exhaust

  1. #1
    Join Date
    Sep 2004
    Location
    Middleton, WI
    Posts
    146
    My Cars
    '86 325es

    E30 Exhaust

    I have an '86 325es and am considering finding a used 325i exhaust and then to take out the cats and resonators(or whatever is in there, haven't seen one before) and weld in straight pipes so I would have straight pipes to a muffler of some sort. Who's done this before, or if you haven't is there a better performance option that i'm overlooking??? Oh, also will a 325i exhaust bolt up to my 325es manifold or will I need to pick up a used 325i manifold as well??? Thanks a lot. The main reason of doing this is that i want dual exhaust running back to reduce the pressure. Give me some feedback on what's best for more performance. And I don't care about sound, I'll have a muffler on the back.
    -Marc

  2. #2
    Join Date
    Oct 2003
    Location
    Santa Clarita, CA
    Posts
    10,161
    My Cars
    E30 Turbo
    Sounds like a great plan but you do need the 325i manifolds aswell. I'm not positive on the "e" ones bolting up or not but they are much more restrictive and the 325i exhaust would do much better with the matching manifolds.
    BimmerHeads
    Classic BMW Specialists
    Santa Clarita, CA

    www.BimmerHeads.com


  3. #3
    Join Date
    Apr 2004
    Location
    Southern California
    Posts
    926
    My Cars
    The Bimma.
    The 325i exhaust will bolt up to the Eta manfilds no prob.

    Exhaust ports on both engins are the same exact size so the monifolds are the same, except the runners on the Eta's have a slight curve, and the 2.5's are stright.

    Top: ETA
    Bottem: 2.5



    I don't know if he minds me quoteing him so I'll leave his name out but most of you guys have heard of him.

    when I dynoed my car when it was a 325e, it put out 115 RWHP with the Jim C chip and exhaust. A friend of mine in Florida with the same car, same mileage (at the time), and same mods (except the exhaust) put out 109 RWHP on the same type of dyno, so I'm gonna assume that you'll get a 5-6 HP gain.
    Last edited by NoName; 10-26-2004 at 03:17 AM.

  4. #4
    Join Date
    Mar 2004
    Location
    Littleton, CO
    Posts
    1,572
    My Cars
    07 X5, 02 325iT
    If you're going to cut and weld everything into straight pipes anyway, why not just go to an exhaust shop and get one custom bent? Also, the general consensus is that a 2.5 inch single pipe all the way back is a great way to go for the M20, so that's something to consider.


    BMW CCA Member #480924

  5. #5
    Join Date
    Dec 2003
    Location
    Columbia, SC
    Posts
    540
    My Cars
    '71 & '74 VW Karmann Ghia, '87 325
    since we're comparing 2 different cars, and there are so many variables, you can't really draw any definite conclusions about performance gains. i think 5-6 is a little generous based on what i've read, but who knows, i haven't done it.

    if you do do it, do the environment a favor and weld in a high perf. universal cat. they flow pretty well.
    i win.

    for sale: es front spoiler with mounting stuff. pm for details

  6. #6
    Join Date
    Sep 2004
    Location
    Middleton, WI
    Posts
    146
    My Cars
    '86 325es
    HAHA, well my step-dad and myself are kind of our own custom shop. He owns an automotive shop so I have access to most everything. Looks like i'll have to pick up the 325i manifold for extra flow and proper fit. Do you know where I can pick up high-flow cats for the 325i exhaust (looks like I'll need 2)?????? BTW, the engine has already been bored w/ new sleeves put in, new piston, all new oversized valves w/ a port job on the head, and the whole engine essentially blueprinted. I will be ordering the chip for it sometime this week as well.

  7. #7
    Join Date
    Aug 2004
    Location
    Sacramento, CA
    Posts
    78
    My Cars
    1985 325e
    one cat one silencer? i remember reading that you don't need the exhaust manifolds, you need the 2.5 intake manifold, otherwise the upgrade is worthless.
    I'm just fine. It's the world that is wrong.

  8. #8
    Join Date
    Sep 2004
    Location
    Middleton, WI
    Posts
    146
    My Cars
    '86 325es
    I guess we'll try to figure something out, I don't want to go overboard on things by any means. People with eta's, let me hear what you guys have as far as exhaust setups go.

  9. #9
    Join Date
    Aug 2004
    Location
    Anacortes,WA
    Posts
    301
    My Cars
    1988 325is

    straight pipe

    i was thinkin of straight piping my car but i was told for a local enthusiast that i would lose torque due to not enough backpressure but gain some hp....id rather have more torque....

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