I've got a custom dual system with 3" x-pipe and dynomax bullets. I want to add cats for inspection purposes. How much hp will I lose by doing this? Is it possible to gain hp?

Would I gain or lose on track times?

 

Zero if they are halfway decent cats. IT is possible to gain some hp or torque if it optimizes the backpressure and exhaust velocity. But that would need extensive calculation of extreme luck. I am under the impression that modern cats are fairly efficient, and some people just like to bad mouth them. It is possible to lose some though.

 

I am assuming due to the nature of my setup, that I will lose hp. I think I'm flowing way too much air out right now to sacrifice anywhere. I need to make a decision soon though. I'm either going to buy some hollowed out cats or just get some high flow cats.

How big are the stock cats? If they're too small, where can I get somet hat will fit a 3" setup?

 

I would say if you use cats with a large cross section, not the little
bullet type, you will lose 5 rwhp max.

 

Read this tech writeup and then make your decision:

http://www.randomtechnology.com/technical.html

Thomas.

 

Check out the Carsound cats. part number 94109, alot of people use those

I just ordered a pair of cats through these guys: http://216.178.81.107/iwwida.pvx?;it...0%201?comp=ppe
*Just copy and paste this mess into your search bar*

 

I still have cats on my car and it dosen't seem to run any worse than cars that don't have cats. There isn't that much hp locked up in the cats.

 

You don't need to worry too much if you use two high flow cats like you are saying. I also recommend the carsound cats. Looks like you would be at least good up to around 340 rwhp before the cats start holding any significant HP back. See this article:

http://www.installuniversity.com/ins...n11.122001.htm

Dan

 

Excellent reading material!

 

Hi Dan. I have not seen you around lately. Great article too.

 

No offense, but you're not pushing a lot of power either.

 

lol Can I use high flow cats on a 450rwhp 383cid and 200 wet shot?? And they change the sound ? idle sound or anything?

 

I did...and they clogged, came apart and basically turned to crap. I have since deleted them and going to a true-dual setup.

 

I see So to decrease the sound (idle sound) can we use a small muffler? (same size as cats) Any hp loss?
- I have problems with cops

 

The cats certainly help the noise issue. Are you suggesting a small resonator or race muffler in lieu of the cat? In addition to whatever cat-back exhaust you have?

A pair of hi-flow cats with an effective muffler (Borla, Magnaflow, etc.) will really quiet the car, plus it eliminates that raw fuel smell which is an obvious sign of no cats.