Hello honda-tech, i have swapped a b20 into my ef, converted obd1, an i am at the point of ordering a header. My question is if upstream or downstream o2 sensor location matters when buying a header an using a p75 ecu.

I dont want to purchase a header that has a downstream bung for o2 if my ecu requires an upstream o2 sensor, or vice versa.

Can anyone tell me what o2 location i need, upstream or downstream for my p75 b20.

thanks in advance to anyone that can help me out!!
even if you arent certain through an opinion out there so other people can help with the post. THANKS!!

- Beef

 

Use an o2 sensor from a 94 integra.

 

Obd1 only uses 1 o2 sensor. Just make sure its before the cat and after all 4 pipes merge together. They are typically located just past the oil pan before the cat.

 

Your original 1-wire O2 sensor in the EF chassis was "up-stream" and close to the head because it doesn't have it's own heater circuit, and thus, is heated by elevated exhaust gas temperatures near the exhaust port. The 4-wire OBD-1 O2 sensor used with the P75 computer is usually mounted behind the oil pan... after all four tubes have merged to get an "average" reading. The heater circuit inside the sensor warms it up to proper operating temperature, so mounting it close to the head/exhaust port is not necessary. The proper header choice then would be one with the O2 bung near the collector of the header, and not in one of the primary tubes up front.

 

Thank you guys for your replies. Motorvations, that was exactly the answer I was looking for, extra thanks to you!