Fuel Injection Tuning

I have a mild build 383 with manual transmission and QFI's Fuel Injection System. I got it running and now I'm trying to dial in the VE Table. I have the Adaptive Learning OFF and I'm trying to tune the VE Table RICH (12.8:1) so that when the adaptive learning is ON the PCM will pull fuel from the table and the target A/F ratios right now are: Idle 13.5; Cruise 13.8; and WOT 12.7

I'm slowly tuning the VE table. I take it for a ride record the screen, go home watch video and increase the VE table where it was lean. Sometimes when I am driving and I let off the throttle the rpm doesn't drop down quickly, it will hang up around 1500rpm for a little, or when I press in the clutch and let off the throttle to shift the RPM hangs up there it doesn't drop like it should. Anyone know why it would do this? Throttle should be snappy, go down almost as quick as it went up.

The "hang" is mostly likely related to the IAC (Idle Air Control). The IAC doesn't close right away on deceleration. It slowly ramps down to a close with a "hang" somewhere slightly above idle before it returns to the idle settings.

I'm not familiar with QFI, but Holley's Terminator system has a full set of IAC parameters to tune this. IAC Hold Position, Ramp Decay Time, RPM Above Idle to Start Ramp, and RPM Above Idle To Re-enable Idle Control. You can read here for reference, but I don't know how it will translate to the QFI.

Terminator EFI hanging up on higher idle.

With the QFI system all you can really do is adjust the IAC value to a certain range using the idle set screw. I did that once I'll have to take it for a ride tomorrow and check it again.

When I had the old Commander system I could not get the IAC "what I want" I simply disabled it and adjusted the thing with an idle screw. Other than about 30 seconds at cold start, it worked OK that way.

wish4hemi said:

The "hang" is mostly likely related to the IAC (Idle Air Control). The IAC doesn't close right away on deceleration. It slowly ramps down to a close with a "hang" somewhere slightly above idle before it returns to the idle settings.

I'm not familiar with QFI, but Holley's Terminator system has a full set of IAC parameters to tune this. IAC Hold Position, Ramp Decay Time, RPM Above Idle to Start Ramp, and RPM Above Idle To Re-enable Idle Control. You can read here for reference, but I don't know how it will translate to the QFI.

Terminator EFI hanging up on higher idle.

Click to expand...

------yes.
the wrong lsa on the cam affects this a bunch .

The problem of not returning to idle, is most likely too much ignition timing advance around 1500 RPM and below, at low MAP (high vacuum). Bump the advance down, just to get it to return when warmed up.
Then work on fuel, too lean can result in jerky misfires, on coast. A good down hill stretch helps tune for that.

KitCarlson said:

The problem of not returning to idle, is most likely too much ignition timing advance around 1500 RPM and below, at low MAP (high vacuum). Bump the advance down, just to get it to return when warmed up.
Then work on fuel, too lean can result in jerky misfires, on coast. A good down hill stretch helps tune for that.

Click to expand...

I only have 10* advance at idle, and all in is 34* by 3000 rpm. I don't have any vacuum advance setup yet. I'll retard it 2* at idle to 8* and see if that changes anything.

My thinking was the use of electronic advance features. Since you are not doing that, and no vacuum advance, best leave timing where it is. The problem is more certainly, too much air, at closed throttle. So as others have said. Things like IAC,throttle idle position, vacuum leak.