A friend of mine that works at the local exhuast shop wants to make my 93' YJ- catalytic converter set up to be easily removed and replaced, for easy reinstall for smogging, but to be rolled without it the rest of the time. I know with the older mass air flow sensors (on Chevy's)... you can get away with it. And, actually gain a lil more power. But, on later Chevy's with the speed density FI... It screws with the system. I was under the impression that the newer YJ's (92-95) were using a similar "speed density system" on newer Chevy's. My questions are- will it hurt the fuel injection mixture and cause my Jeep to run screwy? Or, Will not bother it at all? Has anyone tried this?

Not sure about the YJ.....but on my 4Runner I removed the CC completely and have had no probs with it.

I was going to remove the CC on my YJ but I don't need to anymore so I am just leaving it on. The big thing is whether or not the O2 sensor is located on the CC, if it is then this will cause a problem for you.

Crawl underneath the JEEP and see if your O2 sensor is located prior to the CC just a couple inches forward of it. If so then you are going to have probs IMO.

I'm not sure of what engine is in your jeep but I have a 4.0 in my 93 YJ and have replaced my cat. As for the o2 sensor its mounted on the collector behind the exhaust manifold a couple of feet in front of the cat. If you want the performance with out the restriction of the cat just replace it with a high flow cat thats what I did. I made the exhaust tone deeper and is completely legal. I got mine from summit racing along with a flowmaster muffler. I think the cat cost like $70 or so its made by catco. Any ways when I took a look through it all i saw was a thin screen and my hand on the other side. So its pretty much like a straight pipe.
Good luck
Nick

If you have an OBDII vehicle (TJ) you will have two o2's, the pre-cat O2 measures the fuel mixture, and the post cat measures the amount of carbon the cat is filtering (or whatever cats take away.)
It's possible to fool your computers by hooking up a resistor instead of an O2. On the pre-cat sensor this would not work, since that is needed for fuel mixture. But post cat basically just sets off the check engine light if the cat isn't working. So the resistor would make the vehicle think the O2 was present and sending a healty exhaust signal.

The problem with this is I have no idea what resistance a Jeep O2 makes when the cat is working. If someone could figure this out you would be all set.

For pre OBDII vehicles removing the cat has no ill efects on your engine except for the loss of low RPM torque because of the loss of backpressure.

Hope I helped!

it will work, but you will be surprised in the amount of torque that you will loose, your take off will suffer greatly and the only gain your going to notice is top end.

its not so much the converter giving you the back pressure to have the torque you have as it is the expansion chamber of the cat. so hollow it and have the best of bolth worlds, and yes I've tried it all three ways, with one, without one, and with a hollowed one, hollowed one was best.

Hey thanks guys, that was great feedback. I'm going to check into your suggestions this weekend. I'm also going to try to find an old cat to gut out and see how that works. But, I think I'll keep my original one intact just in case I lose power, or if I have problems getting it smogged.

Yeah I can vouch for no cat at all having ZERO torque. I kinda bashed my exhaust on a rock and the exhaust fell off like a week later. It sucked except that it was loud as hell and I could piss ricers off. Sounded pretty cool high RPM but there's no way its worth the loss in torque.