Hey anyone here gut their pre-cats and install rear magnaflow hi-flow cats? Results? Emissions problems? I live in CT and have a diagnostic test as well as a visual test so I was thinking this would be the closest thing I'd be able to get away with...cause if I ditch the precats entirely I won't pass a visual test.

Plus I'm also wondering if installing the magnaflow hi-flows are really worth it. Do they make much of a difference? or should I just gut my precats and leave the original rear cats?

 

also I live up north and it gets cold....obviously and supposedly thats what the pre-cats are for...for cold start up...so will getting gutting them not let me pass emissions?

 

any cat modification such as gutting will not pass emissions, high flow cats will pass though since they are a replacment, but idk about the pre-cats, I know Patrick gutted his 4.6Ls pre-cats and gained a little power but dont know if it will pass a test.

I could do anything, I have NO emissions though I will act as if I do, I dont wanna pollute.

 

Will gutting the precats and adding aftermarket rear cats trigger the check engine light?

 

nope, as long as there is no O2 sensors, and i'm pretty sure the pre-cats dont have them

 

Hey thanks. That's what I was hoping for

 

This is exactly what I did, CA has the sniffer and the visual.

The pre-cats look like they are there, but are in fact empty.
I've got Magnaflow high-flows in the back.

Passed the sniffer, no problem.
No codes.
And I've got a lot of mods.

You won't throw a code.

IMHO I suggest that you don't let your engine/cats cool-down prior to the smog test, as the pre-cats are there to heat up faster until the main cats are hot enough to function properly. In other words, go at a slow time so that you aren't waiting in line.

 

Why not just gut your cats all together? Don't remove them permanently, just empty them out... Not that I'm planning on doing this soon...

 

yeah if you do not have emissions just gut them cats out or just run high flows.

 

Missouri does a visual/safety check in most areas, and in the city like where my truck is registered, they must pass a sniffer, however since mine is newer, it only has to pass a diagnostic emissions test. No CEL= I pass.

 

Well thanks for all the opinions and advice....if i didnt have emissions id be running long tubes and probably no cats or hi-flows, but that aint gonna happen. So maybe ill gut the pre-cats and go hi-flows, but i still got thinking to do. Next in line for me is a tuner.

 

Why not gut all of your cats and then see if it will pass emissions? If it doesn't, then add the high-flows.

 

My exhaust guy just removed all of the factory cats and replaced them with 2 metallic substrate converters. They don't even look like converters at all. They look more like 2 bulges in the exhaust pipe than anything.