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


Why do I go to MKC Performance? Not only are they one of the only ones with a local dyno, but Chad is an expert tuner of various engine management systems, including the AEM Infinity. Unfortunately, it’s been so long (since before our Castro Motorsports install!) since my last tune that the firmware was really old, and my old files were about three laptops ago for Chad. Silly me, I had not saved them.

Therefore, Chad had to start from scratch. Thankfully, the EMS is so fast and user-friendly that Chad’s experience with it made this fairly quick process. Plus, AEM has a downloadable file for several engines—the S54 inline-six being one of them—go give you a good starting point to tune from.

Here, MKC owner and tuner Chad Charlton is starting the M3’s tune by tweaking the volumetric efficiency map. He monitors everything against the lambda target value (white line), and is seen here trying to get lambda, or air-fuel ratio (green line) to overlay with the white line, the target. As we can see, the low end is still a bit off after the initial pull.

After a couple more tweaks and pulls, it’s starting to get closer and closer.

This graph doesn’t quite show were we started with the base map—at 292 WHP—but it shows Chad getting closer to where we left off last time, with our dyno tests of our lightweight clutch and flywheel from ClutchMasters (red line) in Part 14. He’s picking up power with each tweak. Notice the low end, however, and the difference factory-stock Section 2 made already, thanks to that H-pipe. That’s 25hp right there, which means about 50 lb-ft or torque! Granted, it’s not in a place where it will matter in a drag race, but you’ll definitely notice the difference in everyday street cruising, especially when passing someone in high gear at low RPM.


  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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