No catalytic converter . No problem.
one time i picked up a car for 200 bux .. it was an acura integra . it came with no exhaust .. i wasnt about to spend 400 bux on a new exhaust piece 
but with no "cat" attached. the check engine light would stay on the . the oboII would not allow me to pass inspection.
but one thing about computers ... computer are in fact stupid ...
i needed to copy what the cars computer would see. so to the wires.
our downstream 2ndry O2 sensor. has 4 wires
the 2 wires that are the same color act as a heating element (like a toaster) .. so on a cold start it can heat the O2 sensor up faster for a more accurate reading... any heating element, be it ur stovetop or ur room heater. is 30-120 ohms .. to copy that circuit i used some ceramic resistors in SERIES until i got a total reading of 60 ohms . 10ohmsx6 = 60
the other two wires are the signal wires ... one is + signal to computer and the other is to ground .
so make this circuit and hook it up . what is does is change voltage from ~.3v - ~.8v
... now your still going to have to buy a test pipe to couple the rest of your exhaust together . but a test pipe is 30 bux and this circuit is 7 bux. 
BOOM !!! check engine light off .. now go find ur buddy that is an inspector .
i invest 250 into the car and sold it for 1200. this should work with any honda 88-2004
Nice! I cut catalic, but sensor was good. I just left it outside near exhaust pipe. Good car. Despite it Honda) First rival
of my red coupe on the track)))
You still used the o2 sensor, and had it threaded into the exhaust right? Only difference being you put the resistors in-line with the o2'ss signal wiring?
no sensor . the circuit is powered by the car battery . the circuit changes the voltage on the + signal wire from .3-.8 volts.. the bung plug stayed in the test pipe.
oh, well it would operate better if you still had a functioning o2 sensor threaded into the test pipe.
the ECU takes some feedback from the secondary o2 sensor for fueling calculation, it isn't exclusively for just catalytic operation check. generally when there is a need to eliminate the CEL from a test pipe of high flow cat, a spacer is used to withdraw the o2 sensor from direct exhaust stream, but still keep its operation in check.
You may have kept the CEL from coming on, but not sure if your emissions readiness monitor for the o2 would go ready, which could prevent you from passing a more modern emissions test.
I like that one part "but one thing about computers ... computer are in fact stupid ..."
thanx for sharing
great effort
i follow