Andover Stang

I was installing some new Flowmaster mufflers over the weekend and my
neighbor walks over and said "If you were to remove the cat's
you would gain soime serious H.P."

Is there any truth to this?

Yes I know its illegeal.And no I do not plan on doing it.

But would be interesting to hear if anyone has done this.

I do have a Shorty Headers and some motor work and tune done.

03BottleFedGT

the only thing your going to notice is the exhaust will be alot louder, the hp gain from removing the cats isnt enough to even notice. i dont have them on mine but i wasnt going to spend the money to have them replaced when they went bad last year. and if you live somewhere were the do emissions you car will not pass(unless you know somebody )

mrtstang

Do have the stock mid pipe and cats? If so it will free up a few hp...nothing big though.

socalwrench

Actually, there are some gains to be had from removing the cats- they are restrictive. However, in many states you'll never pass a sniff test, and all of the states tampering with any emissions equipment is illegal (technically).

IRSmart

people do it all the time, it's called an off-road x or h pipe. but you "shouldn't" pass emissions without them (not saying that you won't, you just shouldn't)

cliffyk

I have never seen unbiased, back-to-back--nothing else changed, dyno runs that have proven any power gain from removing the cats.

However I have seen back-to-back, 7800 rpm, runs on my '90 supercharged Miata (12 psi)--using a cheap Advance auto generic cat and a "test pipe"--that were identical for all practical purposes, with the best of the 6 pulls being one with the cat installed.

loweredfourpointsix

ive heard the same thing cliffy.. ive heard that leaving the cats on will actually help on the 2valve but i never knew if there was any truth behind it.

disposablehero27

I've heard both sides, i don't have any on it now, i hear it gives me more power b/c of less retriction, however i've also heard that it hurts, because i have no back pressure... i'm not exhaust man, so i just leave them off for the sound...its a mean sounding mother F*(kr

tanbuddy

When i added a off road h and jlt ram at the same time, i picked up about 2 mph in the quarter, it got me over 101 mph so i was worth it for me

MJH78

when I put my prochamber on (which involves removing all cats, OP), the exhaust note was priceless to me. Power wise..I don't know, it seemed to pull a little better up top, but I also noticed a loss of power down low. I've heard some people say you don't lose any power down low from removing cats, but to me it was noticeable. However, I love the sound and to me it seems you would gain a few ponies on the high end. But "serious HP"? No.