As most of you already know, the Magnaflow exhaust for Evo Xs (part #16823) is a side-in, dual-sides out. To be clear: in contrast to stock, the inlet to the muffler is on the passenger side; after ducking under the diff, the piping goes out to the side and does a 180 to enter the muffler from the side (relative to the car). The muffler, itself, is a standard size for Magnaflows: namely, 5x8x18. The inlets and outlets are in the standard places for Magnaflow offsets, as well. What this means is that you could substitute the muffler that comes with the kit with a plain offset/offset 5x8x18 (e.g., part #14264) and only have it exit only on the driver's side.

Why would you want to do this? Because you could then add a Y before the muffler which would go through a cut-out butterfly and exit on the passenger's side. With the butterfly closed, it would probably be even quieter than the original dual-outlet Magnaflow, which is already one of the quietest 3" exhausts for an Evo X. With the butterfly open, it's a 3" with no muffler, which is how you would want the car at the track.

I've already talked to Magnaflow about this and they will not built it and they will not substitute the muffler. I would have to buy the whole kit, pitch the muffler, unweld the tips from old muffler to put one tip on the new one, and then figure out the Y, butterfly, and other tip. I'm crazy enough to try this (because I want a quiet DD but an open 3" at the track), but before I do so, I wanted people to have a chance to point out what I've overlooked. So have at me.

 

Why not just get a straight-through 3" exhaust like the Cobb, ETS Quiet, Perrin, or Specialty-X? It really seems like you're wanting to go through an aweful lot of work for practically no gains.

P.S. My X picked up 2whp going from the Magnaflow to the Cobb which tells me Magnaflow's chambered muffler isn't restrictive at all.

 

Because, from what I have both read and heard, they are not as quiet as a Magnaflow. It must be very quiet in DD mode (for several reasons).

 

My Cobb catback is no louder than the Magnaflow was. In terms of volume, I'd say they're very similar with the Magnaflow being slightly louder from outside the car during WOT.

 

Or you can just buy MAP's exhaust with that adjustable muffler they use...

 

There ya go, that would probably fit your goals perfectly.

 

Sorry. One other constraint I completely forgot to mention: it must be as tucked up behind the diff as possible for off-roading. The MAP thing looked good until I saw how it hangs. I'll look at the Cobb in a minute.

 

My magy-flow w/ the map 3in mod flows just fine - although a few tac welds are nec to keep the slip fits in place....

 

For the time and effort involved in accomplishing what you described I think you'd be better off just buying an exhaust for the track and an exhaust for the street (quiet.) You could buy used if you want to make it more practical.

 

I have the stock catback with a QTP electric cutout where the cat should be. Its a bolt in style pipe that I can swap out when it comes to SMOG time. So its quiet like stock when I want and wide open loud as hell when I want. It was waay cheaper to do this than buy any catback out there. Just an option and easy. Any muffler shop could do this for you.

 

I wish, but SCCA rules do not allow a dump of exhaust under the car. A car in SM once failed tech at a national event because the wastegate was connected to a direct dump, for example.

 

Love my magnaflow with a tp, looks great and sounds just right.. if anything, i wish it was just a tad bit louder..

 

I love my magnaflow because its so quiet and stealth. Great for those that want a 3" in Socal.

 

I'm debating getting a magnaflow cat back installed, but I'm concerned it won't be noticeable in terms of sound. As a reference, I installed a test pipe and I can't tell a difference with the oem exhaust ('11 GSR).. How does this exhaust sound with a test pipe? I want some deep sound, but nothing that's gonna get annoying as its a daily driver

 

When I put just a testpipe on my stock '11 exhaust it made it a ton louder. Is your testpipe resonated/minimuffler or something?