what up me and my friend were having a discussion about putting a header on my car and i said i was going to install a high flow cat as well. So he says my dad did a test on them and says they dont work.
Is this true?
i keep telling him that there is no way that it is true. Just thinking about it logically should tell u that it works. Having the same amount of free flow throughout the system should benefit the engine the most right?

What do u guys think?

 

Do they work? yes they flow better.
Do they free up HP? maybe 0-1 HP at best but in some instances could lose HP because it can slow down your exhaust velocity.

 

Slowing down exhaust velocity should only happen if the high-flow cat ID was too large. Going from 2.0" inch exhaust system to a 2.25" or from a 2.25" to a 2.5" shouldn't warrant a loss in HP.

 

I think the gains are more as in cases like mine, where the cat is a smaller diameter than both the piping entering from the collector and exiting from the cat

 

That's what jeddy wants to do. He's going to be buying a header, and already has an exhaust. I told him he should buy a hi-flow cat as well if he plans to get a header. But another friend of ours said that there's no need, as it wouldn't help him at all.

Although the gains will be minimal, if you're gonna do I/H/E, you might as well do hiflow cat.

 

2 WORDS...
STRAIGHT PIPE...

 

oh yeah dont forget to get mendrel bent piping...
or just run a test pipe...

 

Pretty much everthing is covered. Now search and learn the backpressure theroy. No need to start new, a lot of good info acrhived.