Dual exhaust question?

[bigg]

2000 Z71 i have four 02 sensors 2 before the cat & 2 after the cat..i would like to remove my cats and replace with pipe , im already running true duals with flowmasters super 44's.. my question is what will i need to do to the 02 sensors?? second question if i just cut off the cat after the 1st 02 & before the 2nd 02 it should be fine right?

 

[creedcop]

I believe you have to keep the o2 sensors, but if you go get a tune being Vortec they can cut power to the back o2s off.

 

[puckhead]

I dont know for sure but IIRC you can get rid of two of them. The other two are system critical I think. If you have a tune or are going to get one from BB or whoever. Tell them this and I believe they can deactivate them from the computer. All of this is rough from memory so double check.

 

[SunlitComet]

front two are for helping the efficiency of the engine so the cats can do the best job they can. The rears are used for monitoring the efficiency of the cats. The rears can be tuned out but it is still advisable to keep the front ones. Is it not illegal in any states to cut off the converters? If you are worried about flow magnaflow makes a bolt on high flow assembly for your state for about $250 street legal and retains all emissions fittings.

 

[bigg]

thanks guys

 

[Southernoldschool]

Results of your efforts

Hey Bigg,

Just wanted to provide feedback on your efforts, as I recognize your truck to be what I just traded for and am now driving. Leaving the back sensors in has caused the "Catalyst Efficiency Insufficient" code to appear on the computer. I am installing spark plug non-foulers to counterbalance this problem, as I have read elsewhere as to be one resolution to this. I still might shop around for some cats to put back on as it is probably the best resolution.

 

[sbowen]

I'm not 100% clear on the question but you have to have data from the upstream o2 sensor before the cat and from the downstream sensor after the cat. Those 2 readings tell the computer in your vehicle whether to richen or lean your air fuel ratio.

 

[SunlitComet]

Not entirely true. The front sensors play the major role in long and short term fuel trim. the rears primary job is to monitor the efficiency of the converters an a minor role in short term fuel trim.