Project E46 M3, Part 17: Preferred exhaust, MKC/AEM tune


We’re keeping the Scorpion exhaust since its tips aligned perfectly, is lightweight, and sounds great as well.

This is the section 1 from Megan Racing we’ll be keeping. Those two resonators come in handy when we’ve got a goal of achieving these “off road” power levels at the least amount of expense to sound level and sound quality as possible.

Here’s the factory BMW section 2. Notice the resonator, which makes you think it would be an X-pipe upon first glance. Still, we don’t know how restrictive this might be inside. There’s one way to find out…

I borrowed Modified By KC’s bore scope to confirm that it is indeed just a normal, straight-through resonator. It does not appear to be restrictive, thank goodness.

A crossover pipe like the “H” seen above is used to provide an expansion area for exhaust pulses. Both sides of the H-pipe have exhaust pulses pushing against each other, stabilizing the stream of exhaust from then onward. This also helps to scavenge exhaust at low end and, thus, improves low-end torque. It may not look like a lot, and it really isn’t more than a pipe between two pipes, but what it does is significant. Just ask BMW, which put it there. Or, better yet, let’s see the difference on the dyno! Let’s go ring Modified by KC’s doorbell…


  1. Dear All
    Just read your exhaust articles on the E46 M3. I’d like to replicate what you did with the VAC / Fabspeed headers, standard cat section then Corsa cat back. I’ve looked on VAC’s website but they only appear to sell Active Autowerke Performance headers ( Can you comment on this please? Do you think I’ll get the same / similar results that you did. I would like the slight improvement in power, no drone, decent quality and fitment, etc. My car is mainly road going with some track days.
    Thanks in advance for any help.
    Kind regards, John

    1. hi John, the droning issue will be taken car of at the mid-section and back/muffler end of the exhaust, especially the back. As long as the AA headers are similar fitment (legnth-wise) with the previous Fabspeed/VAC units, you should be fine, and I would assume make similar power, too. But that’s a question for VAC. Personally I’ve never had any problems with AA products, and I ran a lot of it in my earlier “E36” days. All of their exhaust stuff fit well, too. And if you still decide to go with Fabspeed, may just have to get them direct, is all, if VAC doesn’t carry it anymore. Thanks for reading, and best of luck!

  2. Thanks very much for the response. I have emailed Fabspeed as it looks like they only do left hand drive fitment but mine’s a right hand drive. Will see where this goes. Appreciate your help.
    Regards, John

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