i have an 05 F150. it has the factory 4 cats. i am looking at replacing the rear 2 cats with electric exhaust cutouts. what size pipe does the factory use for its rear 2 cats?

 

2.5"

 

so the factory ford system runs dual 2.5" pipes into a single 2.5" pipe? wow

 

2004+ tailpipes are actually 2.75", but the rest is all 2.5". The Y pipe is a 2.5" dual in to 2.5" single out ( very restrictive ) and a 2.5" exhaust to muffler.

 

i have a 3" y pipe back into a super 40 dumped after the muffler. how loud will it be with the cutouts in place of the rear cats? how will it oerform?

 

Heres my truck after we chopped out the rear cats ( before installing new pipe, so pretty much open pre-cats )

http://www.youtube.com/watch?v=mqBxX...e=channel_page

 

thats it they will be coming off next. what would happen if i gutted the front 2 cats?

 

You would get a check engine light for cat effiency P0420

 

2.5" is what i'm using.

 

The ideal place for your cutout, if you have to have one, would be directly after your Y pipe. In that case, you'd need One 3" cutout. I don't really see a point in running a cutout for both sides of the motor. (Or a point in using cutouts at All for that matter) It'll be plenty loud, no doubt about that, with or without the rear cats in place, louder of course without. (Notice, no one said anything about it sounding GOOD, but it Will be LOUD.)