I've got a ac autotechnic muffler , and i'm getting the cat back done thursday...

should i go with 2.25 or 2.5" pipe?

and should i leave the cat converter in or out?

 

make it a true cat back.....leave the cat in....and go with 2.25 tubing....and make sure that the shop mandrel bends the tubing....not crimp bends.

 

thats what i was thinking but people tell me take the cat out for more horsepower?

 

I would go 2.5" piping, with cat untouched. Stock cat-back piping is already 2.25", is it not? I would leave the cat in place to remain legal and to not void your warranty. What I would do, obviously, is have the resonator removed. It is planty loud enough with the cat in place, and performance isn't too shabby either.

 

Making mandrel bends requires huge, specialized machines that weigh thousands of pounds and cost tens of thousands of dollars. The chances that a muffler shop in Newfoundland will have this sort if equipment is pretty minimal.

If you really want mandrel bends, you need to figure how many you'll need to assemble your system, then mail-order prefab bends from somewhere like Jeg's or Summit Racing. However, a well-built crimp-bent system will make almost as much power for a lot less money and effort.

Also, using 2.5" tubing will just make more noise and kill low-end torque without significantly increasing horsepower. The stock 2.0L Protege engine is not particularly high-revving, and it really can't even use the full flow capacity of 2.25" tubing. The stock ECU's rev limiter will kick in before the engine reaches the kind of rpm's necessary to take advantage of 2.5" tubing.

FWIW.

 

very good point....I didn't notice where he was from.....