Light throttle, low RPM and overrun mapping of fuel

[NOTORIOUS VR]

I seem to see a general trend in the cars I've mapped and not sure if others are seeing the same.

But it seems like the low MAP points (20-35 KPa) and low RPM (1200-2500) usually require quite a bit more fuel then say @ 45 KPa.  So my fuel table graphs are always sloped upwards as the pressure falls to allow the engine to run with a decent AFR.  Increasing ign advance doesn't seem to help too much and actually makes some cars run even worse (jerky).

Not comparing to some of my studies with factory ECU's like Motronic, most of the time they have a low/light throttle map I'm guessing for high resolution in that area.

Any suggestions and comments on this?  Are other people finding similar trends on their mapping?

[gunni]

I do have the opposite. very low load sites tend to be even less then 40kpa range.

[NOTORIOUS VR]

An that is how i think it should be... less load/rpm the less fuel...

But if I tune it that way it seems that most motors tend to run lean while trying to maintain that rpm/load site in a low gear.

Maybe it's something with the inj settings causing this?  FWIW, it doesn't matter what injector type and size I'm using.  Just a general trend I've noticed which is why I am asking this.

I'll post up a VT map in a bit to show what I am going on about.

[BigD]

Are you usually using MAP multiply? In that case it could make sense, esp if your granularity is low in the low map ranges.

[NOTORIOUS VR]

Yes I am... still it's very strange... injector control on injectors as big as 980cc's (x6) is smooth as glass @ 1.0 lambda...

Obviously some cars are more sensitive then others in the areas I'm speaking of, I'm just curious if I'm the only one with this issue so far or do others just accept it and tune around it like I do?

I'm going to try a few things with one car soon, just start playing around and see what happens

[GintsK]

I think it depends on injectors linearity at small opening. We have no such injector characteristic graphs implemented in ECU. So our VE becomes uneven at low loads. Bad thing - VE table is not valid on significant different air temperatures than at tuning moment because inj pulse time is different...

[MWfire]

your injectors settings are wrong. You have to little inj open time. Try to increase VE table for 10%, if lambda drops for 10% injector model is good.

[NOTORIOUS VR]

understood... I'll give that a shot! Thanks!