I want to check my AFR’s, but my car currently does not have a second O2 sensor bung available. I have a Power FC, so if I set it to the ‘No O2 Sensor’ option is it reasonable to install the wideband sensor in the O2 sensor location? Obviously it will work, but what I am wondering is whether I will get accurate A/F readings relative to how I normally operate the vehicle, which is with the O2 sensor enabled.

It would seem like the PFC would go into open loop whenever positive boost pressure of any consequence is detected, and the closed-loop function would only be active during cruise with negative manifold pressure/vacuum conditions or maybe during very low positive boost. But I don’t really know for sure how the logic works. I have a nice ECM-brand A/F analyzer and I’d like to verify my car’s A/F without pulling to cat or DP to weld in a second O2 sensor bung if possible.

So the question is, will the A/F’s during boost conditions with the PFC set to the open-loop setting be the same once the closed-loop setting is reestablished?

Thanks in advance!

 

Apparently the wb sensor wont last long if placed there. Needs to be down towards the end of the dump pipe before the cat.

 

to more directly answer your question, the Power FC's closed loop fuel control isn't that great, and most people turn it off with the o2 feedback option. It only operates in a narrow cruising area anyway. It's not used at idle at all, because that's where the air injection pump supplies fresh air to the exhaust ports to lean out the mixture.

 

Thanks for the replies, guys. Sounds like my idea would work from a recording point of view but not so good from a sensor longevity point of view - I assume from the high exhaust temperature of the rotary compared to a piston engine? I have placed A/F sensors in individual header pipes very close to the exhaust port of piston engines before with no issue - but I don't want to destroy my sensor just checking A/F's.

 

yes, exactly.

 

Reading will be fine in the stock location but the sensor won't last long. You want it at least 18" away.

 

I second what IRPerformance stated.

Most wideband manufacturers state the sensor needs to be 18-24" downstream of the turbo and/or collector.

 

Thanks everyone. Very good info. I was hoping to be able to check my AFR's using the O2 sensor port but it looks like I will have to pull the exhaust and weld in a second bung...