superman

will a engine lite come on if cats are bypass
i want to put a set of headers and remove the cats x pipe it with two flowmasters but i dont want any codes popin up

Ty

they might, but not if done right, you could also go with high flow cats.

wde3477

Suggest you will want to keep the O2 sensors. There is some kind of fake-the-computer-out bypass available, at least for the rear sensors - but I don't know offhand why anyone would want to eliminate a feedback parameter for engine control.

wesbilly

will hunt you down and fry your behind. Isn't that illegal? Well maybe muffler shops just can't do it. I thought those were required. I could be wrong. Don't the cats create some required amount of back pressure? I thought you might be opening a whole can of worms by doing that. Anybody know this for sure?

BTW, glad you don't live in my neighborhood.

wde3477

Suggest it's certainly illegal to modify/remove emission equipment - however, there are still many parts of the country where vehicle inspections are not required or if required, not stringently enforced.

BroganF150

I thought CATs just helped not to redline or somethign like that not to blow up and you shouldnt have a problem as long as the O2 sensors are infront of the CATs

Ty

cats are part of your emissions system that help make your exhaust cleaner, but at the same time, create unwanted back pressure.

wesbilly

I thought it was required- or at least better - back pressure. I never thought that it might be "unwanted". This forum is so interesting sometimes- it is definitely worth reading.

NGM

The Catalyst system is designed to burn off excess fuel in the exhaust. They are restrictive even the high flow cats. The rear oxygen sensors are there ONLY to monitor the cats. The front oxygen sensors set the fuel mixture paramaters with the air mass sensor, map sensor (if equipped) and a variety of other sensors. If you remove the cats and in some cases even if you install high flow cats the CEL (Check Engine Light) will come on on OBD2 vehicles. If your truck was built before 1995 then you do not have sensors after the cats and you can removed them at your own risk without a CEL. If you do have sensors after the cat you have to get MIL Eliminators. They are plug ins that trick the computer into thinknig the rear O2s are reading low emissions. Another thing is to get a tuner and turn off the rear oxygen sensors.

ZV 5.4L

No doubt you get more flow without cats, around here its a hudge fine if your caught.

The only reason to eliminate the o2 sensors would be to run leaded race fuel.

Who makes a SS downpipes and high flow cats?