can you?

[Bojangles1432]

I am a older man and recently just found this forum. My son has a 94 z28 6spd with many performance additions. My question was that he has a exhuast systems with no cat and a dynomax muffler he wants to to weld a cutout were the cat used to be. I wanted to know if there is any problem with this since it has the stock exhuast manifolds. there is a 02 sensor faker there so im not worried about that but just the not having any back pressure with stock manifolds. so will it work thanks

[N20LT4Bird]

Unless you consider the obnoxiously loud noise a problem, no.
AS long as you are not creating a leak in front of the O2 sensors, you are OK. I dont know how he is running O2 sims on a 94; somebody correct me if im wrong, but the f-body didnt have rear O2's until OBDII (96). Running the sims on the front with a stock PCM program will be a problem. You will still have enough back pressure with the manifolds and pipe down to the missing CAT.

[Injuneer]

N2OLT4Bird is correct.

You can not use an O2 sensor "faker" (aka: "simulator") in the pre-cat O2 sensor position. This would prevent the PCM from operating in "closed loop", resulting in poor fuel milage and possibly fouled plugs. You can only use a simulator in the "after-cat" sensor position, and 93-95 model years are OBD-I and do not have after-cat sensors. These were only added to 96 and later OBD-II models.

Running a "cutout" in place of the catalytic converter will not cause problems like burnt valves. It will sound loud and obnoxious (IMHO) but that's a personal preference. Some people will also argue that the reduced back-pressure will cause a loss of low-end torque, but I don't think that is realistic.

[TimeLord]

My exhaust/muffler sponsor made me a cut out that went in place of the cat like you want to do.

I forget if it was before or after I had the headers installed.

Either way,got to the track and did 3 baseline passes then opened it up,and made 3 passes for comparison.

The car didn't run any quicker or higher MPH,the 60 ft was a little worse so basically there was no gain.

the NOISE/RACKET/DIN was horrible,it sounded like a 1972 clapped out Bonneville with a busted muffler,and at the other end it was HORRIBLE. It exited under the passenger door and was SO LOUD and SO UGLY as noise,not enjoyable in any way.

The piece is sitting on a shelf in my store,I removed it immediately after those runs and will NEVER reinstall it !!!!!!

[Bojangles1432]

yes i studied on that obdi 1 program and i see how it does not any sensor or faker that was my bad. as for the cutout thats my sons choice wether he wants to do it. Thanks for the advice and clearing up that problem. As for my car a have a 1972 nova i bought that year ive had it since. It has a 350 60 over 260 cam holley 650 double pumper and many other modifications. The only problem was recently i had to rebuild the rear end. It used to be a 10 bolt now its a 12 with 4.10 gear up to a th350 with bm shift kit. My goal is to still beat my son. But eventually he'll probably get me. the difference is he can drive his every day i cant even get out in the ran without a severe scare. Timelord your car looks great how many years have you been working on that. I guess having a sponser helps some on bills.