The only problem was that all of the valve systems I could find seemed to switch between shitty sounding and super quiet and fully straight piped, unrefined loudness. The ideal system would maintain the exotic tone even with the valves closed and would simply become a louder version of that same tone when open.
It then occurred to me that the only companies that are incentivized to make their car sound good, regardless of valves being open or closed, would be OEM manufacturers looking to maintain their signature sound regardless of valve position. I took stock of cars that had been made with similar displacement V8s that produced the same frequency ranges that I was looking to maintain with my new setup.
To me, one of the best sounding smaller displacement V8s ever made is the Maserati Gran Turismo 4.2 and 4.7 V8s. After a bit of research I discovered that the 4.7s all came with valved mufflers from factory that were actuated by vacuum. A quick trip to eBay revealed that these mufflers could be had for about $700 used. I also discovered that they use the same two and a half inch diameter piping and have two exhaust outlets per muffler. So it was possible that I could retrofit them theoretically.
At this point, I knew I was potentially going deep off the reservation into uncharted territory. But for $700, the risk felt tolerable with the opportunity to have something truly unique and at a cost comparable to even the cheapest of aftermarket systems. I ordered a set off eBay, and a few weeks later they arrived.
When I brought them to my local exhaust shop, the shop manager thought I was completely insane. But after going through the layout of the system, he conceded that it was potentially possible and got to work trying to implement it. I give them all the credit for making this Frankenstein system work.
To prevent having to fabricate up fresh connecting pipes, I brought an additional rear section that I had laying around in my garage and had them harvest the connecting pipes and exhaust tips from that system to graft onto the Maserati mufflers. They then fabricated small adapter pipes that connected the harvested connecting pipes to the mufflers as well as small connectors from the Maserati outlets to the M3 factory exhaust tip locations.
Much to everyone's disbelief, it actually all fit.
We then installed an ECS tuning universal exhaust valve actuator kit and hooked it up to the Maserati valve ports. I keep the remote for the valve controller in my center console and I think this is the first in the world E92M3 to use Maserati Gran Turismo valved mufflers and it somehow all works.
Now for the sound, it's absolutely insane.
With the valves closed, almost all of the lower register of frequencies is successfully cut out and doesn't drone except for a tiny window at 2000 RPM, as many E92 systems do, and the higher frequencies where rasp would be are completely cut out without killing the midrange tone. One of the things that I liked about the design of these Gran Turismo mufflers is that they don't simply choke the exhaust flow by closing a valve on the main exhaust path. What they actually do is route the flow through a muffling chamber that uses smaller diameter piping to both raise the resonant frequency and also reduce the overall volume of the sound without completely killing the tone that was coming through the system already. Interestingly, the harder you drive the car, the quieter the exhaust actually sounds as the extra gasses create turbulence in the system that washes out the sound. But when cruising around with the valves closed, you still get all of the tone that the motor produces.
When open, the car absolutely screams, but still has a refinement to the sound that, as cliche as it sounds, is nothing short of exotic but with a filled in meatiness down low. It is without question the best sounding car I've ever driven, and the best sounding system I've heard on an e9x. The open valve path in these mufflers still utilizes a small amount of resonation internally, so there's still a rasp reduction happening that smooths out the gnarliness that these engines are capable of producing, leaving a clean, crisp, wailing shriek.
I'll do a proper video documenting the modes both inside and out as I really think this is one of the best systems you can put together for the E9X platform.
