O2 sensor placement

[64plymouth]

I bought an a/f gauge. I’m wondering about o2 placement. I have an evac fitting in collector. I’m taking off exhaust system and putting on header extensions. Can I sensor in extension? Or so that to far from merge. Or do I have to lose evac fitting?

 

[threewood]

It needs to be about 8" after the collector. Angled down so moisture doesn't collect in the sensor, and directly in line with exhaust gases.

 

[64plymouth]

Ok that’s good to hear. I thought it had to be further upstream

 

[pnora]

It also needs to be in the 10 to 2 o'clock position. Not horizontal or pointing up. Needs to be pointing down to keep the moisture away.

 

[64plymouth]

Will only 10 inches of pipe after sensor be ok

 

[PRHeads]

I would think any air pulled into the exhaust from the pan-evac would affect the readings.

My experience with pan-evac systems and exhaust systems is they don’t play well together.

If the O2 is fairly close to the open end of the pipe, the readings at less than WOT won’t be super reliable……..so only use the gauge for tuning WOT.

 

[kiwigtx]

From the Holley Sniper installation instructions.....

 

[6PKRTSE]

Do not use the bungs that put it in going in at a 45 degree angle. I did it for under car clearance. It does not allow the O2 far enough in the tube. Gives a false reading. Found this out on dyno. Re-welded in a regular 90 degree bung and been fine since.

 

[64plymouth]

Ok so if I install sensor in extension close to where it bolts to collector should be ok and cap evac pipe so no air can get pulled in

 

[PRHeads]

Yes.
Make sure the gasket for the extension is good.

 

[64plymouth]

Thanks

 

[Budnicks]

I would think any air pulled into the exhaust from the pan-evac would affect the readings.

My experience with pan-evac systems and exhaust systems is they don’t play well together.

If the O2 is fairly close to the open end of the pipe, the readings at less than WOT won’t be super reliable……..so only use the gauge for tuning WOT.

that's what I was thinking too
EVAC it can also contaminate the sensor

if the EVAC was farther down stream, farther away from & after the O2 sensor
like the O2 sensor in the area of the EVAC & relocated the EVAC farther down
in the header extension
maybe could use both (?)

 

[INTMD8]

I would think any air pulled into the exhaust from the pan-evac would affect the readings.

Yes that is correct.

If keeping the evac you would need to put it as close to the beginning of the collector as possible, or even in one of the primaries.