VersaTune User Forum

Bringing this thread back from the dead. Updated to 1.13.144 today and glad to see they added the ability to disable p2096. This CEL was a nuisance for us lean burn guys. I haven't explored the software for other possible changes, but maybe they fixed the issue with not following commanded age too? I'll be taking some logs again as I had some fuel trim issues I'm trying to straighten out.

If you are commanding lean AFRs, leaned than stoich, as long as the secondary O2 sensor is connected the ECU will try to bring it back down to stoich.

mituc wrote:If you are commanding lean AFRs, leaned than stoich, as long as the secondary O2 sensor is connected the ECU will try to bring it back down to stoich.

Agreed with this. I have disconnected my secondary O2 sensor personally.

mituc wrote: ↑March 26th, 2020, 4:02 am If you are commanding lean AFRs, leaned than stoich, as long as the secondary O2 sensor is connected the ECU will try to bring it back down to stoich.

Thanks Mituc, I finally got around to pulling the secondary o2 sensor last week, and the car now follows the leaner AFR under low load situations.

Ok, in the meanwhile I tested quite a bit on my cars. I ended up commanding just slightly leaner AFRs than stoich. the fuel economy did not improve much by going a lot leaner, past that point where the ECU will panic if the secondary O2 will start yelling about it. With these values I could also reconnect the secondary O2 as it does not complain any more.

Going that lean on the spark plugs I could see some white deposits accumulating, which is an indication that the engine is burning oil. This doesn't happen with the slightly richer AFRs but still leaner than stoich. My guess is that when the engine is hot because of the lean mixture the excess of air inside the cylinders starts oxidizing the oil vapors/film.

How lean are you commanding? Also have you played with commanded spark advance at these low loads? When I had an AP, I did a cross country drive with lean afr at cruise RPM/Load and was getting better gas mileage than my wife's Ford Fusion (4 cylinder) and consistently getting over 30 mpg when filling up.

mfinlay04 wrote: ↑February 13th, 2023, 7:17 am Also have you played with commanded spark advance at these low loads? When I had an AP, I did a cross country drive with lean afr at cruise RPM/Load and was getting better gas mileage than my wife's Ford Fusion (4 cylinder) and consistently getting over 30 mpg when filling up.

Yes I did. However after prolonged lean burning during long cruises the oil starts to oxidase and you will find white deposits on the spark plugs. After reconnecting the secondary O2 and using a still lean (above stoich) but richer burn that problem disappeared.
So the fuel economy still relies on your right foot. If you want fuel economy then just don't drive fast, blend into traffic and that's it.

mituc wrote: ↑February 14th, 2023, 12:07 am

mfinlay04 wrote: ↑February 13th, 2023, 7:17 am Also have you played with commanded spark advance at these low loads? When I had an AP, I did a cross country drive with lean afr at cruise RPM/Load and was getting better gas mileage than my wife's Ford Fusion (4 cylinder) and consistently getting over 30 mpg when filling up.

Yes I did. However after prolonged lean burning during long cruises the oil starts to oxidase and you will find white deposits on the spark plugs. After reconnecting the secondary O2 and using a still lean (above stoich) but richer burn that problem disappeared.
So the fuel economy still relies on your right foot. If you want fuel economy then just don't drive fast, blend into traffic and that's it.

Can you share your low load AFR targets? I'd be curious

Sorry for the late reply.