Open loop afr

[myburb]

I am using 6395/7427, $OE, advanced $OE TP5 v250. There is a parameter "open loop afr enable" and "open loop afr vs temp vs vacuum"
if you enable how does it deal with the table. Being as you are in open loop the nb supposedly not controlling but still indicating, would it take some calculation from within the bin and add? Hoping someone might know.

[dave w]

My explanation might not be 100% correct?

The PCM "Assumes" the VE table is correct. The PCM calculates Open Loop AFR from the VE table, by adding / subtracting injector pulse width for an "Assumed AFR".

I use Wide Band O2 sensor readings to adjust the "Open Loop AFR vs. Temp vs. Vacuum.

dave w

[myburb]

Thanks Dave, your confirmation makes it worth while to burn some chips experimenting.

[myburb]

Well I did some testing and it does work as advertised. Whether there is any real use for it I don't know. If you have a correct ve table that is what you want you don't really need any corrections. I do think that it can be used in closed loop if it set right and that might be of some value to some. Some time when I'm bored I will try it. In the trucks gm doesn't use it and whether that is an emission reason or something else I don't know.

[Kitch]

So do changes made in the Open loop AFR table alter the values in the VE table or do changes in the VE table alter the values in the Open Loop AFR table?
I currently have Closed loop disabled and I'm running directly off the VE table. If I was to check the "Set" box for Open loop AFR enable what happens?
By the looks of the Open loop AFR table the only areas of any use are the ones highlighted in the lower right corner?

[lionelhutz]

Changes in either will not alter the other.

If it is using that table then it will calculate the fuel to get the AFR entered in the cell where the engine is operating. If the VE table is accurate then the AFR will be accurate.

I'm not sure why you think the highlighted cells are the only ones being used. Low to medium throttle causing acceleration will move you to the middle of that table. Heavy throttle might get you close to the left before you trigger AE.