Wideband O2 sensor location?
 

Would it be OK to install an O2 sensor behind the headers? I have ceramic coated headers and don't want to weld a bung in them and have to re coat. If the sensor was behind the gasket between the header and the exhaust would it create too many problems with potential air infiltration, or can I get a good enough seal on that joint?

I run my mine directly after the header collector for years now for the same reason. No issues. At one time, briefly, I had two there, and they both verified each other. Just gotta absolutely ensure no leaks.

I have mine also, just after the collector. If you flanges are sealing good with a gasket I see no issues.

It would be fine right there. If you have a leak at that connection, having the oxygen sensor in front of the leak won't matter. It will create a false reading regardless.

For the best accuracy on an o2 sensor, you want no upstream leaks and about 18" of leak free pipe behind it before exhaust exits to atmosphere.

Thanks all! Been worried about that.

Timely topic since I just ordered one yesterday. I have the ram air exhaust manifolds and Pypes down tube. Planning on putting the sensor in the down tube. How close to the flange should I put it. Thanks

Opinions will probably vary, I'd say ~"24 away from the exhaust flange on the head.

Mine is on the driver side, just after the collector. It's been there for years with no issue.

^^^ This

^^^^
SAME

Tom V.

Usually the car dictates it to some degree. Easy access for future maintenance is one thing to consider.

You can put it as close to the flange of an exhaust manifold as you want so long as it's easily removed/installed. Down the pipe several inches doesn't hurt anything either.

On header applications I put them in the exhaust pipe after the header collector flange.

In the Holley software there is an adjustment for the 02 if you end up down stream a ways, that affects how fast the 02 reacts, so you don't get an AFR reading that is jumping all over the place.

Attachment 603333 I placed mine after my shorty header four years ago. All good. Hope the attachment worked.

Something else to consider is mounting. They want the sensor mounted at about 10* up to prevent contamination from moisture. A little copy/paste for you. Also, remember to disconnect your battery if welding on your vehicle.

A weld-in M18 X 1.5 boss is supplied for sensor installation. Mount the O2 sensor in the
exhaust system at least 18 inches downstream from the exhaust port. If you anticipate
high EGT's (over 800C), run a turbocharger, run at high RPM for extended periods of
time or plan on running leaded race fuel then you must mount the sensor at least 36
inches or more downstream of the exhaust port as all of these can cause the sensor to
overheat. On turbocharged engines the sensor must be installed after the turbo charger,
if not, the pressure differential will greatly effect the accuracy of the unit. For accurate
readings, the sensor must be mounted before catalytic converters and/or auxiliary air
pumps. To prevent collection of liquids between the sensor housing and sensor element
during the cold start phase, the installation angle should be inclined at least 10° towards
horizontal with the electrical connection upwards, see below.