XFI pulling fuel but actual A/F higher than target

[MSDGN]

I'm confused...looking at a recent XFI log my actual A/F was 11.3-11.4 in some frames...target is set at 11.3 but it's still pulling fuel...O2 correction is at -7 to -9%...shouldn't the O2 correction be close to zero or maybe be adding a little fuel?...I'm just not getting a handle on XFI...doesn't seem to respond the way I think it should...do I need to tweak the VE table some more?...how fast does XFI respond to fuel changes?...as an example if the actual A/F is 11.0 and target is 11.3...should you see a correction in a few frames...1 frame...10 frames?

 

[HighPSI]

Scott,
You need to look at the average A/F in that area vs the actual. Looking at a few frames may not give you a true picture. Based on what you have posted, I would tweak the VE table

 

[MSDGN]

Thanks Cal...so I'm assuming I would lower the values in the VE table around those frames...what would be a good starting point in the VE table...lower the values by about 2-3%...or should I go in bigger increments?...if I'm getting say O2 correction of -7% should I lower the value by 7%?...I'm sure it's not that linear....or easy...

 

[HighPSI]

Thanks Cal...so I'm assuming I would lower the values in the VE table around those frames...what would be a good starting point in the VE table...lower the values by about 2-3%...or should I go in bigger increments?...if I'm getting say O2 correction of -7% should I lower the value by 7%?...I'm sure it's not that linear....or easy...

If it is taking out 7% then lower the VE table by 7%. It's that easy. To lower a a group of cells by 7 percent, just highlight them, then right click and select Trim/Percentage Trim and type in -7.

One thing I want to caution you on: When you are moving the throttle, there is AE fueling going on. The same is true if the MAP is changing rapidly. What this means is, when you are not at WOT, it is best for a beginner to let the ball stabilize in that square before you tune it.

 

[MSDGN]

OK...the only values I have tweaked in the VE table so far have been at idle and at WOT from a 1/4 run...

 

[SloGN]

something you might what to look at is the Gain percent table and the negative gain table.

What you might be seeing is the effects of the wideband is seeing the Actual A/F and the ecm is adding or subtracting the fuel and over correcting the A/F thus causing the A/F to swing above and below the target A/F.

Triming the gain tables some may help with this.


HTH


Cal is the man on FAST :biggrin:

 

[Blazer406]

Check out my old thread......

My old thread

We had the same problem... never did figure it out.... we ended up fattening up those cells in the VE table.... and tweaking the - correction % to where it couldn't pull out any fuel at those few cruising cells...

HTH