posted on March 13, 2017 14:08
Here is Project M3 sporting a Khoalty rear diffuser and Scorpion exhaust from Bavarian Autosport. Finding the exhaust combo to work with the VAC/Fabspeed header setup has been a real trick. Prior to the headers we had the Corsa cat-back, which was perfect as long as the headers were stock with the cats in place. The system flowed well, didn't drone, and it sounded great. After the headers, however, dang! So, after a few different trials, we think we've find a good combo that not only keeps the weight down, but also the sound decibels and drone, all while fitting perfectly well and making the necessary power. Make sure to check out the video capturing the sounds on Pages 4 and 5!
Project E46 M3: Part 17 – The preferred exhaust setup and more AEM tuning by MKC. It’s all about keeping those VAC headers!
I tell ya, life would be a lot easier if we'd stayed with the stock headers. When we tested our headers from Fabspeed/VAC Motorsports in Project M3 Part 3, the increase in power throughout the power band was intoxicating. We knew this was one upgrade that would be staying on the car.
Unfortunately, this presented a problem, considering our goal was also to keep the car quiet and drone-free. While our Corsa cat-back sounded perfect with the rest of the stock exhaust system in place, and was probably one of the—if not the—freest flowing cat-backs out there, it proved way to loud the cats not in place anymore. I encountered this very thing with my previous E36 M3, when I’d gone with a Corsa cat-back exhaust with it as well. The car sounded great, again, until I went with a racing setup up front.
We tried different setups with this E46 M3, including a full header-back Magnaflow system from Bimmerworld, but with the cats off the drone was unbearable between 2400-2800 RPM. Using a Magnaflow with the stock cats in place gives an E46 M3 a nice, deep rumble. Still, nothing seemed to work well with our headers we still wanted to keep—at least not until we came across the Scorpion exhaust and Megan Racing system from Bavarian Autosport in Part 15.
With the Scorpion/Megan combo, the overall exhaust note was nice, and the drone was better than before, but some of it was still there. Also, due to the elimination of the factory H-pipe on the factory Section 2, we hypothesized this could be costing us a bit of the loss in low-end torque. Some folks have even mentioned it in the comments section, too (good catch, "TheAxiom" and "Obioban"!).
Luckily for us, the Megan Racing Sections 1 and 2 piping can be separated to fit just like the factory sections 1 and 2, and one could replace one piece or both. Therefore, we decided to keep the front half of the Megan Racing piping (Section 1), and go back to stock for our Section 2, which retains the H-pipe and even adds a small resonator. And yes, that makes it four different companies’ exhaust components on this car, before you ask—so let’s hope they all fit well!
This is our exhaust setup as we left it after last time in Part 15. It starts with the VAC/Fabspeed headers (which you cannot see), followed by Megan Racing’s sections 1 and 2, and on to a Scorpion section 3 rear muffler.
This whole dilemma has been about trying to keep the exhaust system quiet, lightweight, and making the most power as possible. But in order to accomplish the latter, it means we have to keep these VAC Motorsports headers on there. Unfortuantely, because they are cat-less, they don't help keep the system quiet! However, because we want the power, we're going to figure out a way. There's got to be a way, I say! (And no, turbocharging is not an option right now).
The stock BMW Section 2 (left) will be what we’ll be replacing the Megan Racing Section 2 with on the right. Notice this part of the Megan Racing has no resonator, nor an H-pipe crossover section (see top).