Hey I did some wideband dyno runs tonight and the first run netted an air/fuel ratio of about 14.5 :1 and O2 mv in the 800's. After richining out the wideband to 13.1:1 the o2's reading in the 600's? I thought lower numbers were leaner!! Why is it showing leaner while the wideband was showing richer??What is going on with that? Any insight would be great. FYI it is a SD system with tunercats, datamaster, and the motor is in my sig.

Thanks

chris

The stock O2 sensor is only good for reading rich or lean of stoich.
That's all....

It's also sensitive to backpressure and temp., so it would sound like that you changed the AFR enough to change the EGT enough to further skew the oem O2 output. Note, sounds like, hard to tell from over here.

Don't forget to read the plugs, they are the best record of what's going on inside the chamber.

Grumpy,

Is that to say that a WB O2 is insensitive to backpressure changes? I understand its heater is much better than any NB. So location for a WB is not real critical within reason compared to a NB?

On a related question, does this heat and backpressure situation help to explain the following? Mostly stock '90 305 TPI Camaro with SLP headers. Heated O2 about 12-15" downstream from factory location. Prom edited to allow closed loop @ 30 seconds which it does. BLM's typically 15-ish lean for a short time after startup regardless of ambient temp then move toward normal. Doesn't matter if it's first startup in morning or after normal operating temp, stop 10 min. for gas and restart. Is this still an O2 temp thing despite the heated O2? Previous nonheated O2 would drop into open loop during extended idle, but not with the heated one.

I'd enjoy your comments. Thanks.

Regards,
Gary Anderson

Thanks for the replies. One thing I did notice was that on the last two runs where the O2 volts were lower is that the car had not gone into closed loop yet. We were trying to get a few chips in and while the car was warm it had not timed into closed loop yet. I will log some more today to see what the mv are around town. Thanks for all the help


Chris

I don't know about your Z, but my corvette with its '165 ECM and $32b code has 3 fields that determine how long it is till closed loops is achieved.

Cold Engine O2 Timer: 300 secs
Warm Engine O2 Timer: 206 secs
Hot Engine O2 Timer: 66 secs

You could program the hot one to a lesser value to get it in faster while at the dyno since the O2 sensor isn't even needed in WOT so who cares if its up to temp yet.

For N/A cars, there's no real mounting limitations for a WB, other then say mounting it 10'+ from the engine. The delays in reading, and COOLING effect of the exhuast gases, are down sides at that distance.

FWIW, the WB sensor's working temp, is about 1,800dF where the heated oems light off at about 600dF.

Racing and using closed loop, is going to generate inconsistant results, with some codes.
If you want to race and or do serious dyno work, then I'd suggest developing a BL Lock patch, so no closed loop corrections are applied to WOT. Otherwise you're you might just be working against the BL learn function.

There are also some hot restart timing corrections is some cals.

If the oem O2 is allowed to cool then it will quit working and the engine will go open loop. Using a heater one, keeps it hot so that it will continue to work.

While the EGT at the port might be 900-1,800dF it quickly drops as it goes down the pipe. By the exhaust tip it's hardly much warmer then ambient air on some appls..