MSefi.com read only forum (Jan.15,2018)

I'm planning on locating the O2 sensor in my Chevelle's H-pipe, at least 4-5 inches behind the header collectors. I bracket race this car regularly and have removable header caps for when I'm at the dragstrip. These openings are in front of where the O2 sensor would be.

Obviously, while at the track, I don't care much about closed-loop operation, but I do need it to idle without loading up, and I do drive at part-throttle up the return road, through the pits, etc. Primary consideration at the track is WOT power and consistency, though. I understand EGO correction wouldn't be used during full throttle. I'm just concerned about loading up when running low RPMs/low-load around the pits, etc.

If my VE table is sufficiently tuned, can I just turn EGO correction off when I open the headers and hope for the best? Or should I consider locating my O2 sensor right in the header collector so that it is functional whether my caps are open or closed ?

If I end up just putting it in the collector, I imagine I can buy a cheap 1-wire O2 sensor, but if I locate it in the H-pipe, I'll need a 3-wire heated sensor.

Anything else I need to consider?

If you get your VE tables set up correctly, you can disconnect the O2 sensor and run open-loop 100% of the time. The O2 sensor is there to allow for not having the VE spot on, and for changes that aren't exactly accounted for by the other sensors.

When i use our "snifer" O2 sensor on the dyno, if the end of the snifer pipe is too close to the end of the tailpipe, we see extremely lean air/fuel ratios because of exhaust reversion. Fresh air is actually being sucked in and altering the O2 sensors' reading. I have to make sure the snifer is at least 16 inches into the tailpipe. Anyone else ever seen this?

Even in a stock vehicle, if the donut gasket is bad it will suck air into the exhaust and mess with your O2 sensor.

GL