[Ralphie]

I cut out my cat, and I have a 40 series flowie w/ a 2.5 in. exhaust from the Y-pipe back, I bought a O2 Sim from Summit but now I'm thinkin my gas milage took a dive because of it, could this be? I'm talkin 50 miles on a 1/4 tank intown drivin, if this is the problem I want to put a cat back in but I wanna know what kidna to put in that will flow good but not cause the SES light to trip out. Thanks.

 

[BlazerLT]

I would reinsert it.

The hi flow cats don't restrict your exhaust that much to notice a difference, but you will notice your fuel economy go up which will be nice for the wallet.

Did you reset your computer after you cut the cat out?

 

[Ralphie]

Yeah I did, and put a scantool on it to erase all engine codes.

 

[Ralphie]

Bump.

 

[MuddyS10]

um...put it back on. Factory cats and high flow cats flow about the same amount of exhaust, so either put your OEM one back on, or go buy a catco or something.

 

[Ralphie]

Anyone else?

 

[Rhansen]

The converter won't seriously hurt performance, but it will quiet the exhaust note.

 

[350*s-blazer]

ok a little basic info on obd ll. the upstream o2(the one closer to the engine or before the cat)is the one the computer reads for injecting fuel. the downsteam one(the one after the cat) is ony used to monitor the efficency of the catalytic converter. so basicly it justs makes sure the cat is working properly for emmisions. so with a o2 sim plugged into the rear o2 plug and the upstream o2 still in place it should not affect fuel economy. what will is the added power of no cat and your lead foot! trust me once you do mods to make your car faster the more you want to enjoy that added power and more you press that pedel to the floor. but hey thats just my opinion.

 

[Ralphie]

Awesome info, thanks! I'm pretty sure the fact that I like to have it hold out the gear a little longer doesn't help, but it sounds good!