what kind of HP gains would I get if I removed the cat ?

 

That is an excelent question. If anyone has that info, I, along with many others would love to know how much HP the cats are robbing.

The problem is going to be getting a muffler shop to do any work on it. They can be fined big time if they are caught messing with any emmision equipment. I'm sure there isn't an off-road pipe available yet, either.

Sam

 

There really isn't much HP being robbed by the cats. In fact, the exhaust system isn't doing much to limit horsepower at all. Header, cat removal, and aftermarket exhaust combined result in less than 10 horsepower gain. The real place to make power (as has been previously stated) is in forced induction or engine work (cams, high-compression pistons, intake manifold, EMS, etc....).

Cat-backs and intakes are the most commonly used "aftermarket upgrades" because they don't void your factory warranty, won't jack up your car (like bad engine work might), are reasonably affordable, can be installed by do-it-yourselfers, and are dyno proven to give additional horsepower at WOT (usually 5 - 10).

 

I disagree...

Cats tend to rob quite a bit of HP and there can be a much bigger gain than 10 HP total in my opinion if the whole exhaust is uncapped. Now, this is comparing apples to oranges, but my 2000 Mustang gained the following...

10 RWHP - O/R H-pipe
11 RWHP - MAC cat back
13 RWHP - Long tube headers/h-pipe

I'm no better than anyone else in that I'm just guessing the potential of our vehicles. I want to see actual dyno results from someone who has done these mods. No need for bench racing (or dynos in this case).