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Thread: Exhausts and cats; Eiberspaecher

  1. #1
    Join Date
    Dec 2004
    Location
    Sydney, Australia
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    Default Exhausts and cats; Eiberspaecher, etc

    Hi all,

    I've been messing with exhausts a while now and learned a good many things that are not apparent on these forums.

    1. It is extermely hard to find these at a reasonable price in this part of the world.

    2. don't mess with BMW exhausts; try to keep them stock. Many shops will offer to custom fab an exhaust using fibreglass packed resonators and mufflers- and these simply do not perfrom well.

    Owning several e34s, it is clear to me that each BMW exhaust is tuned to the engine, the flow and noise it creates, the size of the mufflers, cats, etc. BMW design the bends differently depending on the engine type, as well as basics like pipe diameters. Whilst one might think bigger is better, think about this;

    I had severe intermittent running problems with my M50 525, which had a custom resonator and a 535i muffler. The resonator had been damaged as it hung a sharp edge down and the PO had caught it on something. When I got the car it ran like ****, so I welded the holes up and changed everything that could be at fault- all the hoses, intake connectors and seals- even the coils, sensors and checked everything many times. The car ran well sometimes, and others very poorly, like on 4-5 cylinders (though it was uniform poor running accross all cylinders- ie lean or rich). Having done everything, I experimented with different types of fuels and found that a lot of things affected it, the most being ambient temperature.

    The resonator in the meanwhile occasionally broke around the weld zones I was creating and did not do a good job of making a decent tone even when it was sealed. However, in the short periods that the muffler was selaed, the engine performed flawlessly.

    Finally, after much messing around, I found a reasonable price on OEM exhausts.
    1. the thing just bolted in as easy an anything
    2. the quality was excellent- much better welds than most exhaust shops manage to do
    3. It fits perfectly. Custom fab jobs are common in Australia due to the availability of OE exhausts. Every one I've seen on one of these cars hits the body somewhere or hangs down lower and is vulnerable to being hit.
    4. Custom-fab jobs invariably vary the length and diameter and obviously back-pressure. A BMW tech once told me at a dealership that my nice shiny stainless custom fab job would reduce economy (this was on an M30 running early Motronic). I didn't see how a free-flow exhaust would do that- but after a few years driving the car I found this was the absolutely true. I recently swapped to a OEM exhaust having rebuilt the engine, replaced injectors and AFM etc. Economy did not improve in a big way until I got rid of that exhaust.
    5. Custom exhausts are of course required if you carry out a major modification such as forced induction, ***but not for ECU chips and other minor improvements***. BMW exhaust design is clearly one of the reasons you buy a BMW, so don't screw around with it. Moving from an OE 525i exhaust to a 535i exhaust is not a good idea at all. Everything is slghtly different, so plug and play is more about prayer and pain. Even year and market models vary, so go by your VIN when ordering parts.

    BTW; having finally found the best way to source cheap OEM exhausts here in Australia, I thought I'd share it with you all. Will help you if you need to buy one.

    NOTE:
    All these are proper BMW spec parts, last for ages and are the only real solution IMHO, as explained above:

    e34/e32
    530i/535i/730i/735i (inline 6)
    Resonator $460
    Rear muffler $450

    e34
    525i M50
    Resonator $360
    Rear $400

    M70 e32
    750iL
    Rear $660
    Resonator $660 (complete with original 'square' tips)

    Prices are all AUD, inc GST. (AU dollar is low at the moment).

    Can help you to ship overseas if you arrange freight and buy a few.

    If you need OEM Cats I can supply these also. Proper OEM cats, not replacements that flow differently and limit performance.

    Nick

    TAGS: Bosal; Eiberspacher, SuperSprint; muffler, resonator, glass pack, catalyst, catalytic, catalyst, cat, cats, back pressure
    Last edited by genphreak; 12-05-2008 at 09:30 PM.

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