Hey guys, I recently just got classic plates for my car and don't need to get a PA emissions test. I was wondering if gutting out my cat would cause there to be too little backpressure and actually make me lose hp instead of gaining a little. I have edlebrock tes headers and a 3" cat-back. Any input??

 

No no no no, don't gut a cat. Never gut a cat. You know why? When you gut it, you've just created an expansion chamber. So the air coming in hits that open area and expands to fill it. Then it has to SQUEEZE back down into the pipe on the other side to exit. This in itself creates backpressure. Run a pipe THROUGH the cat. That will remedy your problem.

And for clarification, backpressure is never bad. However, lack of backpressure makes a motor 'more efficient', which actually SHIFTS the powerband towards higher rpms. So it can actually shift power OUT of your normal operating range, and add it up top. That's why big exhausts will kill low-end....it's all pushed into higher revs. What can also happen with an overly large/overly free-flowing exhaust is over-scavenging between the period of exhaust and intake valve overlap.

 

Thanks for the help Nixon1!

 

also, its bad on the atmosphere.

 

take the cat shields off and tac weld them over a piece of regular exaust pipe. new its all equal and you won't have the restriction of a cat in the system.

as for the environment, i say plant a tree

 

other than the legal and enviornmental concerns, is there any performance concerns to either replacing or removing a cat in a basically stock setup?

 

Yes there are performance concerns - you'll get more performance without the cat.

Never gut the cat - straight pipe it. That is absolutely right.

 

Modern cats are made so well that any power loss from them is minimal, and often not noticeable to the driver other than in maybe a reduction in exhaust volume..... If you're keeping with a stock-type setup, I say stick with a cat, do the environment a favor. But if you're going for a high-power buildup, ehh, might as well ditch it.