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When the logger is turned off, should the O2 line on the graph go up or down? I have a Sportsman.

Thanks

Sir,

I’m a little confused at the question... did you mean when the engine is turned off not the logger? If so yes the line will show a high number which would "lean" but wont matter as the engine isn’t running so the value is meaningless.

Sorry for the confusion. I mean when the engine is turned off. It was pointed out to me that my O2 graph goes the wrong way when I shut the engine off. My O2 line goes rich or down. Have I wired something wrong or is there a malfunction somewhere?

Depends if you're showing AFR or lambda. If you don't know, it won't matter as the data will be meaningless all the time.

Here's a screen shot of a graph. The bar on the left is marked A/F cyl1, so I'd say it's not lambda. Why would the AFR line go down when I shut the engine off?

What is the sensor control unit outputing? Are you using a Racepak kit? Do you have an equation in the channel properties that converts voltage to a reading?

The O2 is Racepak and the config is whatever the default is from Racepak. I didn't change anything in the Sportsman. I can go into it and look, but I'm not real tech savvy with this stuff. I'm pretty sure the O2 instructions said it was set-up for AF.

Perhaps there is still raw fuel or fumes in your exhaust system with the engine off? You turn off the engine so there is no more exhaust flow and it was probably running rich near idle?
Does it always stay like that even after a while? Can you remove the 02 sensor from the exhaust and then do the same test and see what it does? Be careful of the 02 heater, don't burn yourself or anything while doing the test.

I don't know of another racer whose O2 line goes down when the engine is shut off. I'm wondering if there is a problem with my unit or my installation.

Hi Ron,

i recognized this kind of O2 reading too in the past - i think it depends on what happens when shutting down the car and the exhaust setup.

For example if you shut down the car by cutting the ignition but there will be some fuel delivered to the engine until it stops turning then its possible that in this last second the A/F ration goes richer. If you have some silencers/catalytic converter then the fresh air from the end of the exhaust will need a lot more time to mix and clear out the rich gas mixture in the exhaust zone where your O2 sensor is located.

To be sure the sensor reading is correct you can take out the sensor when it shows rich and the engine stopped with the cable still connected. Be sure you don't hurt the loom when turning the O2 sensor with the cable connected. It should read lean right when you take out the sensor. Otherwise you can also disassemble your exhaust next to the sensor location to clear things out in a similar way.

Thats also the reason why O2 sensor recalibration should always be done when the sensor is in fresh air and not mounted to the exhaust.
As i cannot look at your car it's anyway possible that there is something wrong but i don't think so.

Regards, Michael