this is pretty aggravating because i think it's affecting my mpg's alot. i have the ve table 90% right, i can't really tune the really low kpa rows because everytime i let off the gas it immediately wants to go rich.. like 11.0 rich. i have 80lb fic injectors with all their data already in the tune. what can be adjusted in the tune to help with this? i don't know anything about transient fueling or dfco, haven't messed with either of them. my current tune is attached

 

Sounds like your DFCO is disabled. If you re-enable it, your engine will stop fueling when you're within the DFCO table parameters. Been awhile since I've messed with a gasser tune, but that's an easy place to start.

 

DFCO is enabled. I've noticed that when your injector size gets to a certain point, like over 60lb/hr...DFCO doesn't do much anymore. The injectors can't flow a small enough amount of fuel at that point when vacuum on decel is like 20inhg..

 

so there's nothing that can be done at all to help with this?

 

Decrease the decay rate on the throttle follower and get on the brakes real hard

 

Larger high impedance injectors are inherently lazy at low pulsewidths, on decel your engine needs very little fuel and a larger injector even at its smallest pulse width may still dump to much fuel. Pulse adder is very important at this point as it compensates for a larger slower injector and commands the injector to fire sooner to factor in the latency.

Long story short it is a inherent problem. Fine tuning can help reduce it but....

 

I would change the default minimum pulsewidth to be the same as the minimum pulsewidth... not sure why they would have it different and higher...

 

Great question , I'm fighting this also with the siemens deka 80's on the 5.3.

 

I wouldn't worry about it, honestly... If everyone was concerned enough about the mileage lost while going rich on hard decel they wouldn't have modifications done to require injectors that size anyway lol. If you want more control of the fueling at low pulse width, get some low Z injectors.

 

And a injector driver.