Off road pipes 431 hp 404 tq. With cats 410 hp tq 389. I put the cats back on 2 years ago to pass emmissions. I had a check engine light so i had it re tuned . I new i was down on power because of the cats. The only thing i didn't like about the off road pipes is that after driving the car for a 1/2 hour I turned green and had watery eyes. Cats kill the smell but kill your hp numbers.

Oh well maybe i'll go back in June.

 

Wow that's a big gain, 20hp. I can't wait to see what my car puts down. The #'s in my sig are w/ cats too. I know taking them out at the track gave me another .15+ and a mph.

I agree though the smell sux and after you go for a ride that's what you smell like all day.

 

so you are saying two years ago, with cats it made 410hp?
but now with a new tune it makes 431 with cats removed?
what brand cats? did they look clogged or collapsed?

 

I wonder what my car would do without the cats and just open headers...

Might have to find out this summer before the pinks allout shoot @ MIR, maybe the exhaust will find itself taking a vacation for that weekend

 

Sorry.
NO, I lost 20 hp by adding the CATs. 2 Years ago with NO Cats I had 431 Hp and 401 TQ ..I wish i gained!

 

damn, those must have been some really low flowing cats. what brand cats? did they look clogged or collapsed? most results are more in line with what DannoWS6 saw

 

My car dynoed with cats 427hp and 385tq ive got the magnaflow cats.

 

The cats that came with the SLP headers. I can't remember.

 

No came on the QTP y-pipe

 

I remember when i took my SLP cats off i gained 15 hp and 15tq in the curve

 

Nice. I remember after pricing a FAST 90/90 and considering the gains, I went out to the garage and gutted my cats instead.

Some day I'll get the FAST....

 

Neat, that makes me think what my car would make without cats.

 

wow, and i always thought good high flowing cats didnt rob alot of power. at least with motors making 500rwhp or less.

 

SLP Cats are horrible.I wonder what you would make if you ditched the SLP header and go with Kooks or QTP.We've seen 10-20rwhp gains.
Kook header Cats work very well.Ussually 5hp or so difference on a H/C car.

 

You can't compare a car tuned without cats to just putting the cats back on without re-tuning. If you re-tuned with the cats I bet the hp loss would be closer to 5-10 hp at the most. It's like dynoing stock manifolds to headers without tuning. Why bother even dyno it.

 

I've done it.Some cats lose alot more than others tuned 100% back to back.Most good cats only lose 5-10rwhp.
An acception was Brent's Vette which gaine 60rwhp getting rid of the Cats.But this was a 427 FI setup.

 

That's why I went with the Kooks 3" catted set up. No nasty stench and minimal power loss. Nice compromise I think.

 

I dunno about hp, but my ta passed with a hollow cat, no tune. So cant see why a hollowed or something that appears to be a cat couldnt be added and left at that and no mess with swapping then,

 

Holy crap that's a big diff! That car is sick though

 

random high flow cats make about 5hp(or less) compare to straight pipes(proven on the corvette forum). ill take that loss over the smell any day