After reading numerous SERT tuning threads I have a question concerning how or V-Twins differ from my 93 Vette's EFI system with regard to "learned" fuel trim in closed loop and how it is applied to PE (power enrichment)mode.

When my Vette's batch fire speed density EFI system is in closed loopit trims the fuel by using short and long term BLM's (block learn memory based on O2 sensor averages over time) to adjust fuel trim, the "center" BLM value being 128 or no trim. On transistion to PE mode (open loop)if the BLM's are less than 128 (fuel trim negative or leaner than the fixed map) the fuel trim is instantly returned to a value of 128 so that the bank is running off the fixed VE table. On the other hand, if one or both banks are trimmed higher than 128 (fuel trim positive or richer than the fixed map) whatever the value the long term BLMholdsat transition to PE mode it is locked at that value instead of returning to 128. The logic here being that if the ecm was having to trim the fuel richer than the base mapit could be harmful to fall back to a leaner setting at the transition to PE mode. Makes perfect sense since going lean at WOT is bad. I know there are a number of other factors applied to theoverall fuel trim (inlet air temp, coolant temp, etc.)but this is the bigone that changes with closed to open loop transition.

Now, with our HD's we have AFV or adaptive fuellearning and this sounds to me like the same basic principle. I've read where Steve Cole has said that the AFV is learned and used in closed loop and also, in some way, applied to open loop operation. What I'm wondering is if the AFVvalues are handled in the same manner as the GM EFI system on transition from closed loop to PE mode. All I've read so far just indicates that the AFV values are applied to open loop but I haven't seen any more detailed explanation as to how.

Can anyone explain in more detail how AFV is affecting open loop operation? Is it based on the AFV values at the time of transition or something other than that?

Also, I may have a couple terms confused. Are either of the below statements correct?

VE new + O2 integrator = AFV
or
AFV + O2 integrator = VE new
or
?

Thanks,
Al.

 

I cannot get into all of it but here is a basic covering of the AFV. The ECM looks at several ways to get the final AFR and stores that information for each calculation. It then compares the arrived at calculation and issues the richest of the bunch. Now the NewVE is what one calculation says the VE should be corrected too at the point your looking at but that doesn't mean that is a value you will find in any table, a micro controller doesn't work that way. The correction values are store just like the GM method but the difference comes in at the end of the calculation. In the GM world they do not use the correction unless it is richen the mixture up but in the HD world, best we can tell, is that it applies the corrections all the time. Open loop, Closed loop, rich or lean and PE mode or as some call it WOT.