This is my Question

[mich_132003]

[/quote]

No, no catalyst is free-flowing if it is doing its job. About 80% of total system backpressure is from the production catalyst. That's why your cat-back exhaust systems only make minor differences in power (10-15 bhp). The Mopar cat-back and most other 2.5" systems are more than sufficient to fully realize the power stated in the upgrade kits. We haven't found any delta from a well-made 2.5" to a 3", so we are selling a 2.5" system. It's lighter, so you'll be faster - right?

Race pipes are almost guaranteed to get you in trouble if you use them on the street because how loud they are - unless you are sneaky. I leave the stock muffler on even when I install the race pipe for trips down the strip and other sorts of power-rewarding activities. So there you have it, my solution to mid-14s.

I've said similar things here ->
http://www.ptcruiserlinks.com/forum/...17&whichpage=2
[/quote]

3Bar - Are u telling me that Magnaflow's advertised Free-Flow Cat is all bull crap.

Another comment you made that bothers the heck out of me - "cat-back exhaust systems only make minor differences in power (10-15 bhp)"
Minor difference ! ! ! ! ! ! hell man - Stage I only gave us 20hp. Please explain what you are talking about - I am having trouble understanding this "tower of babble" that goes on in this Forum at times. Are we talking just to hear ourselves talk and show others how much we claim to know ! ! ! ! [xx(] [:I]

[3BarBoost]

Sorry, people get all hyped about exhausts - expect to get 300 bhp because they bought a 3". It just ain't gonna happen. The 10-15 bhp I stated is extremely generous actually. Most systems only do 5-10 bhp over stock.

The Stage 1 may only make 20 more hp peak, but it makes a lot more everywhere else - which is why it is faster than an exhaust change alone. The very best race pipe without any boost changes will only add 20 hp.

As for Magnaflow's part, I don't know a darn thing about it. However, cats are by their very nature restrictive or they can't CATALYZE effectively. See above comments about race pipes.

[03baggedturbo]

"It is better to keep your mouth shut and have people assume your are a fool then to open your mouth and prove you are one."

I dont konw why I wrote that.. it's just funny.. as long as a crack myself up...

Pretty much everyone makes sense on here.. the 250hp 2.5 exh.. the 300 hp 3.0 exh.. OK I am not an exhaust specialist but I am friends with numerous 11-13 second turbo car friends/ shop owners and with turbos you would like the biggest opening... just run 3inch if you want.. it's not going to hurt you..but the 2.5 exhaust will also do the same thing till you get in those higher #'s then it's not going to dramatically hurt you till you get in the 400hp-600hp range.. ect.. getting an aftermarket cat will also help you.. yes if you want to run a straight through exhaust it will be good but I have done that on other cars .. go to the track and listen.. I am not a big person on being too loud but there is a time when it is too loud to daily drive..

Now lets get back to what we were put on this earth to do.. [^]

[Kirby]

If the Cat is the bottleneck to the system, and you happen to live in an area where removing the Cat is impossible(fines, etc)the best route would seem to be to replace the cat and downpipe first.

I am almost positive that the powers-that-be know this, but are unable to supply this need due to the high cost of verifying that a 3" cat will do the job as well as the tiny little stock one. We should remember that the Cat needs to have the unburnt HC around the ceramic surfaces long enough to burn them. An oversize Cat may move more air, but may not be as efficient at scrubbing the exhaust gasses.[:X]

[ptgtcb]

quote:Originally posted by Kirby

If the Cat is the bottleneck to the system, and you happen to live in an area where removing the Cat is impossible(fines, etc)the best route would seem to be to replace the cat and downpipe first.

I am almost positive that the powers-that-be know this, but are unable to supply this need due to the high cost of verifying that a 3" cat will do the job as well as the tiny little stock one. We should remember that the Cat needs to have the unburnt HC around the ceramic surfaces long enough to burn them. An oversize Cat may move more air, but may not be as efficient at scrubbing the exhaust gasses.[:X]

More surface area of the substrate and we've got pleanty of heat, I don't think we will have a problem.