My wideband a couple days ago starting going richer in the upper rpm's. I was driving on an 80 mile trip and the wideband read 10.6. I tuned dead on 10.8, so 10.6 wasn't really worrying me. Then I saw 10.2 when I got to my destination. (It was late night so I was kind of getting on it on open freeway stretches).

By the next night it read 9.9 when I was coming home. I re calibrated my LC-1 and this morning it was still doing the same thing.

In all the other rpm's the AFR is spot on, just crazy after 5000. The performance doesn't feel any different, and I did a thorough inspection of the engine bay, nothing out of place.

Anyone ever experience this? Any ideas? Thanks guys.

edit: I did change the periphery in V7 to turn off lean spool. Before I had it set to start and end at 2500 rpm. Then I changed the periphery. But I changed the periphery back, and afr still doing the same thing.

 

I'd try a different sensor before making any major changes. They can read perfectly fine at cruise then get all weird at more rich levels.
Dan

 

Was there any major change in temperature or elevation, or even any knock? It could be any number of compensations as well as the sensor going bad, as mentioned.

 

no knock. Logs were dead on too. No changes in load either.

Yes, I went from Bay Area 60 degree weather to central california 95 degree weather and an elevation change of about 600 feet.

 

The temp change could be the cause. There is a bit less O2 in 95º air. Also, less O2 at higher altitude.

Other than that, you could have gotten fuel with less Ethanol than you usually have (if you have E10 fuel over there).

 

Yes, I would say it's most likely the temp change. The stock tables seem to be setup to compensate a bit too much for higher intake temps. I even see it myself from winter to summer...just never tuned it out yet.

 

Interesting. What kind of changes need to be done to compensate for the temp swings.

I know of the ignition timing retard compensation for intake temp tables. If that's the right one, would it be safe to not allow the computer to retard 2 degrees and only 1?

I usually run 76 91 octane, and in Fresno couldn't get anything but shell and chevron so that could have played a role in it too. I use 76 because I make the most power with it on 91.

 

MRFred posted the temp comp tables a while back. I haven't worked on those changes either though. I don't have a gauge on my WBO2 so it's not screaming in my face that it's off, so I can ignore it. lol.

 

The change in gas and ethanol percent could have an effect, too.

Honestly, I wouldn't worry about it. If you have similar issues using the same gas through the seasons at home, then you can start tweaking/tuning it, but with so many variables changing on this trip, it might be a waste of time.

 

I'm going to see if it returns to normal here in a couple days back on the 76 since I'm back home. Thanks for the input guys.