This might be a stupid question but and anyone tell me why when I'm logging AFR ERR the results change from day to day. For example I have been logging my z06 when I drive to work and when I drive home. I can get the AFR ERR within 2.0 in the morning and then when I go home and I log my results are all over the place from -7 to 12. I don't get it. Does amb temp have something to do with it?
Do you possibly have stuff within the tune still active?
Like COT, DFCO, fuel trims, closed loop operation?
I will say that ambient, humidity and density altitude can play around with it a little and that where if you went back to using the fuel trims that it would be correcting on the fly for you.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Thank you for the reply. I have all that turned off. I can get it just about perfect and then when I log again (later that day) to do 4k and up everything changes. It's has to be ambient,humidity and density altitude. This morning the temp is 37* and this afternoon it was 61*.Originally Posted by 5FDP
Another question. How would you tune 4k and up?
Don't you use the PE table for 4k up? Learning myself..
Are you using a WB or are you relying on your O2 sensors?
And for tuning 4k and up make sure you have your PE table set accordingly, about 12.6 for an NA car, 11.5 or so for boost. This is something you will need to be in SD with WB to tune on your VE table. It also helps to create a histogram that plots your commanded AFR on a MAP/RPM graph that matches your VE table. That way you know exactly what you are commanding and where. This is useful for adjusting your PE numbers in the mid ranges, and setting the MAP for PE enable appropriately. I think mine is around 60 kpa or so for enabling PE. This might mess with your numbers if you have it set too low.
Also, there is an OLSD EQ ratio table under fuel. Worth a look if your temps swing around a lot. You can tweak that to get closer to stoich. I just have mine set to 1.0 in all cruise/part throttle areas under normal conditions.
Also, when running rich WB sensors can go out pretty quickly, as in a matter of a few months. Have a few spares laying around if you can afford it.
Thanks for the reply. I'm using a wideband.
Does the WB peg out from time to time, one way or the other? It will really do this with rapid throttle changes. You could have a bad sensor. I've had this same issue before. Threw in a new sensor I got off Amazon for $80.00 and gtg. This was bugging me too for about a month, as it progressively got worse until it was obvious. My VE table went from +/- 2 pretty much everywhere to +/- 20 to 30.
Also worth checking your collector at the header too. I'm sure as you know when things get cold they contract. This can cause small leaks into the pipe. I wrapped mine with foil and used band clamps to seal them up tight. Works pretty good.
And I have noticed on my car to keep an eye on IAT as well. Mine likes to get hot when sitting still idling. This plays with WB readings too, so for gen III's I have to say from experience that temperature definitely has an effect on fueling. There aren't any real good correction tables for this in the PCM for IAT and fuel, as far as I know. I could be wrong there or haven't seen one, but temperature definitely has an effect. There are tables for ECT, but nothing for IAT, which actually has much more to do with burning fuel.
It doesn't peg out but I think I'm having issues with my computer. The same thing happened last week. I rebooted the computer and it started logging correctly. When it starts messing up it will keep showing it's lean in the log but the gauge is reading correctly.
This makes sense. Thanks
I tune the part throttle pretty much the same way I tune the WOT or above 4,000rpm.
If you are using the error it will always show you the error against the commanded, it doesn't matter what RPM you are running at. You can setup a filter if you wish to remove the data you don't want.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Same here. I like to also see what my PCM is actually commanding too (via a simple AFR commanded histogram) so I can get as close to stoich in as many places as possible outside of PE, and to confirm my PE numbers as well. My vacuum pump puke tank has gotten better, but still has a lot of fuel/oil mix in there. It literally looks like coffee creamer lol. This also helps gas mileage and improves WB sensor life. No sense in running richer than you need to.
I've been doing a lot more research on this, as there is a correction you can make for IAT. Go to Engine>Airflow>General>Cylinder Charge Temperature. This table tells the PCM how much to bias ECT with IAT based on airflow. The lower the airflow, the more it biases ECT. I have yet to get to mess with it on my car, since it's undergoing some unscheduled maintenance (snapped the studs on the back of my oil pan), but as soon as it's back up and running I will let you know if I have found a decent way to tune it in the scanner. IPW, IAT, ECT, AFR and A/F seem like good places to start plotting. I'll let you know my findings, and if there is a histo you can make, or not. I like to dabble and try new things anyway. So this is fun for me, and I get to learn something I'm sure.
One example of that is I even have a table for seeing how long my valves stay open in ms. Pretty interesting stuff right there, but useful if your changing your injection target, and getting in just the right spot.
Keep in mind, the PCM cannot account for every variable, so some error while in SD mode can be expected no matter how well you tune it. That's just the way it is there. But this new info should help, I hope.
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