I went from a JBA long tube header, off road h-pipe and MAC axle backs to the same setup and exact same SCT tune with the only change being the addition of a Pypes mid-muffler after-cat system. Here's the dyno chart. The first run was baseline with the MAC axle-back system and the final two with the Pypes mid-muffler setup. I'm pretty amazed.



[IMG]local://upfiles/73912/392B09CDE6FC4B0A842B52F259A97FF1.jpg[/IMG]

 

Looks like about 6 RWHP/RWTQ from a simple change! Good deal congrats! J

 

Yeah I was pretty surprised. Guess that debunks the myth ofcat-back swapsnot providing any gains...

 

Not really, since he already changed everything ahead of the muffs it would seem THE ONLY RESTRICION LEFT was the muffs. With stock setup I don't think only an A/B swap would do anything.

 

Great results! I've had people tell me that a straight-through design muffler, like the Pypes mids, would cause a loss in torque. Your chart disproves that; and in fact, your peak hp and tq moved towards the lower rpms. I've had people say that the power would shift upwards. Very interesting result.

 

You're absolutely correct. I guess we have tocompare apples to apples here.

As for the powerband moving up, I'm not so sure. My powerband did seem to move up after the CAI/off-road pipe/exhaust. The addition of the off-road pipe made it the most noticable. I could tellas soon as I removed the catted pipe that I had more high rpmpower.I should have documented every change with a dyno run like this.Itgets expensive though. I think they threw these in for free because they were busy. They had about 10 other mustangs and lightnings in their 10k sq. ft. shop. When Iwent to pick my car up they had an 03' Terminator on the dyno laying down 450 to the rear. My little n/a s197 was the least interesting car there. lol!