Since the Trophy has a 200 cell cat as standard, but constricts the diameter down to 2.25" at the exit, would it be possible to modify the standard cat to get a 2.5" system from the manifold back or would this damage the standard cat? I want a 2.5" system but I don't want to pay for a replacement sports cat just to get an extra 0.25" as that's a lot off money for a bigger pipe. I'm very tempted by the KTR Ultra Performance exhaust, but does it make that much difference to the performance of the car if you don't have a 2.5" system all the way from the manifold?
Does this modification affect the performance of the cat? My only worry with something like this is that in cutting into the cat up to a point where it's diameter is 2.5" you end up removing some of the cells
Yes, the outlet housing on the stock cat is a conical shape. All you'd have to do is cut the end off until the outlet is 2.5" and then weld a new piece of pipe on.
BTW I've measured my 2005 182 Cup and the cat outlet is more like 50mm outside diameter. So it would be well under 2" diameter internally.
I've just come across Vortex Exhausts by Torque Exhausts. I'm a bit sceptical about their claims, but I'm not sure either way. Has anyone done this themselves or know anyone who has. It's pretty incredible if true, hence my feeling it's smoke and mirrors.