Cat back system

I helped a friend with a header/catback install on a 2k4 1.7liter civic ex automatic. the kit we got from ebay, then also ordered the header, and a downpipe that connected the header to the catback system. the catback was specifically for the LX civic, but it bolted up fine. ps- the car now has no cat, and the exhaust is fairly loud, but not highpitched. total cost was around $350-400

So with no Cat, does that affect the ECU at all? obviously the o2 sensor after the cat would be getting much higher oxygen readings. or do you bypass that sensor by looping it?

just curious, also isn't it illegal to run with no cat?

Why are you running with no cat?

I helped a friend with a header/catback install on a 2k4 1.7liter civic ex automatic. the kit we got from ebay, then also ordered the header, and a downpipe that connected the header to the catback system. the catback was specifically for the LX civic, but it bolted up fine. ps- the car now has no cat, and the exhaust is fairly loud, but not highpitched. total cost was around $350-400

on the 2k4 civic the cat is integrated into the exhaust manifold (large round piece behind the heat shield) the cat was removed for better exhaust flow, and since my friend is not "green" he decided to run without it. also this is in S.C. in the U.S. a state that has no pollution testing or vehicle inspections (at least not for the last 5 years!) so there is no penalty. As far as the CEL or MIL coming on, it did, but we used an O2 sensor isolator to fool the sensor (and the ECU) into thinking the Cat was still installed. worked perfectly and we have no Check engine light!