hey i have a cali spec car and i was wondering if it would throw off the 02 sensors if i gutted the precat on the front manifold. i know it won't add much, but i still want to do it. so i need to know if i will need to get o2 simulators or not. thanks in advance.

 

I think you need simulators or a relocation of the sensors to behind the main cat... if I recall correctly, that's what people did when this idea was first being tried.

Actually, I found one of the threads:

http://forums.maxima.org/showthread....utting+pre-cat

And here's the link to Desert Pearl's write-up:

http://www.desertpearlmax2.homestead.com/Fed_YPipe.html

 

It seems like a lot of work for 2-3hp?

 

edited for accuracy.

and if they were clogged, then you were only restoring lost HP anyway.

 

it's not that hard when you have a lift and air tools. i did my ypipe on the ground in like hour and half. i'll probably just do it and get some simulators

 

I gutted mine and there where no gains to be seen. You will get a P0420 for catalyst efficiency below threshold. I gutted mine cause it was falling apart inside, but it wasn't restricting the exhaust flow yet. Real gains are with headers and not gutting your cat. Plus you are going to have exhaust leaks, since the honeycomb holds a metal ring that is the gasket- between the manifold and pre-cat. You could put some black high temp RTV on there and wait few hours before starting up to stop any exhaust leaks.