Project E46 M3: Part 7 – Magnaflow vs Corsa Cat-Back Exhausts!


With Magnaflow, things aren't very different in this department, but luckily it’s a 30-second fix.  While we were at it, we added an extra piece of silicone under the brace to prevent any other potential vibration coming from the pipe to the brace.


Something else that seemed to come into contact was the fatter UUC rear swaybar featured in Part 4.  Again, a little silicone coupling took care of unwanted vibration noises inside the cabin.


On Modified by KC’s Dynojet 424x, our goal was to have a quieter car with the Magnaflow system, while not losing any of the previous power we got with the Corsa.

In Part 6, with the addition of the exciting AEM Infinity EMS, MKC’s Chad Charlton left us with a stout 327 whp, but that was in slightly cooler and drier weather, as well as with significantly heavier factory wheels.  Years of testing has told us that every new part needs a new baseline, and finding a proper baseline can take several pulls before the car quits making more power. 


When it comes to dyno testing this E46 M3, initial pulls always seem to start off lower than normal.  In fact, today we started with 302whp before peaking at 318whp with the Corsa (blue).  After the install, we started similarly at 303whp with the Magnaflow (red), before peaking at 316whp.  This car has a stand-alone AEM ECU—so there should be no computer “adaptation”!  My red E36 M3—or even Project Supra, for that matter—never had this issue, but it's something that seems to be common in newer cars.

After 45 minutes and about a dozen pulls with each exhaust setup, we found a couple more horsepower with the Corsa up top, with a few advancing ponies by Magnaflow in the midrange.  Is this is a significant difference?  The answer to that is probably subjective in nature.  But we think that, with a difference of only 0.6% and in a very small window, the exhausts seem to perform pretty similar ot each other. 


If you were looking closely at the first horsepower graph, you may have noticed a gain by the Magnaflow from 3500-5500 RPM, which translates to around 3-4 lb-ft when converted to torque.

So, where you lose a little with one, you gain it back somewhere else.  In the end, the average power between the two exhausts seems to be about the same, with fourth gear pulls measuring 9.11-seconds and 9.13-seconds for the Corsa and Magnaflow, respectively.  It really comes down to your price point and preference in sound and aesthetics. 

We feel the goal of quieting the car down without losing significant performance was achieved.  And the fact that we gained a little in the often-used midrange doesn't hurt!

How do the two fair in sound?  Hear the acoustic differences in our video on the next page!


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