Well since two counties in Indiana has emission testing, I have an em1 2000 civic si. i have to use two o2 sensors. One o2 sensor is on the exhaust header and the other one is on the cat. I'm boosting this year. I'm getting a t3/t04E turbo kit setup. The question is.. if one o2 sensor is going to be on the exhaust header and the other o2 sensor is going to be on the cat. This is my first turbo exhaust system, so i don't know if people would run a cat on a turbo exhaust setup. I have to keep in mind emissions. Please help. Thank you

 

I don't understand what your question is... I don't know how they do it in Indiana but most people usually end questions with a question mark (?).

 

Well since you need to convert to obd1 to tune it, you wont even need that second o2 sensor.

 

are the primary and secondary o2 sensors interchangeable? could he use his secondary as a primary on the turbo set up?

 

Ive got a chipped ecu (obd1) ready to tune but i still have both o2 sensors (one at the exhaust header and one at the cat) hooked up. So your saying if im running off a obd1 ecu i would only use one o2 sensor? but wouldn't that throw a check engine code???

 

not with a chipped ecu. i got mine with no use of 02 sensors i think. but no codes with your obd1

 

So which o2 sensor should i use for a t3/04E turbo set up? One off the exhaust header or the one from the cat???

 

first things first, the type of turbo has nothing to do with the o2 sensors. at all. i'm not sure why you have mentioned the type of turbo a few times. maybe a mistake?

the one on the header is the primary o2 sensor. this is the one that reads the a/f mixture pre-cat. the one after the cat is the secondary and is only there to monitor cat efficiency and keep your ecu happy.

however, they are both physically the same on your car, but with different length wires.

obd1 ecu only uses ONE o2 sensor...whatever sensor you have in the primary spot.

if your county uses a sniffer and does not plug the car in, then you just need the primary o2 with that obd1 ecu...and of course a catalytic converter in place. if your county plugs in at the obd2 port like many states do...well, then you have an entire other situation on your hands ; )

 

Thanks for the advice. Yea the county here plugs into the cars computer like you said i think its the obd2 port. If there's no check engine light on, im golden. hahaha

 

you shouldnt have a cel

 

well in this case you will need to convert back to obd2 for emissions. obd2 ecu, stock injectors and cat will have to go back in and no CELs.

 

yep. if they plug into the obd2 port and you have an obd1 ecu installed it'll not communicate and you won't pass. even if you don't have a MIL illuminated, the obd2 port needs to communicate that to them, they won't just look at the cluster.

sucks. that's why i was saying if they do that you have an entirely different situation on your hands ; )