2005 f-150 5.4l so i have dual cherry bombs 2.25in pipe from cats back. but there not load enough so i want to take out the cats and i was thinking of going with 2 in pipe to replace the cats with. Then using the 2.25in thats all ready there. i will get the cheaters and i do not have to pass any pollution tests. What the worst that going to happen if i do that on these trucks

Thanks Cory

 

Emissions tests very from state to state.

One thing you can do is see if there is a direct replacement that is manufactured to replace the cats with either high flow cats or a straight pipe. Summit may have that.

 

what state are you from, and what are there emissions laws? If you "can" do it it will not do anything as long as the o2 sensors are before the cats. If they are in, or after the cats than you will have to put the cheaters in to trick computer. I did the same thing on my 94' F-150, but i only have the one o2 sensor so didnt have to worry about it at all. The smaller pipe may make it sound a little different is all. Smaller pipe= snap/popping noise but better scavenging, and bigger pipe= mellow/ rumbell but less scavenging ability. I think 2 1/2-3 inch is the best.

 

i do not have any test to pass and the o2 sensors are in the cats. so i have to get cheaters i was just wondering what performance and gas milage will do.

 

it shouldnt really change that much.

 

removing the cats is fine but you will have to get the cheaters for the O2 sensors, I would not put the small pipe in place of the cats I would go with the same or a little bigger, a smaller pipe is not going to change much at all or not enough to notice, the only other way to make it louder is either headers or new mufflers or NO mufflers go straight pipes that would be loud enough I think.

 

Your cat monitors (9G444) that are in the cats can turn on a check engine light as an ineffiecent cat. That means that they measure the same readings as your HEGO sensors (o2).

 

A high flow cat may be another option for you. You'll still have the cat and it will be louder.

 

Sorry I'm just an ignorant new poster, but isn't that illegal? I recently bought a 1983 f150 351 and I've read that modifying the emission systems violates federal regulations (EPA). I REALLY want to remove my emissions stuff (no testing in WA), but I don't want the opportunity to get fined. My understanding is that this is a very LOW oppurtunity for the EPA to enforce this law, but I don't want to take a chance.

 

That's about right.