I'm in the same boat...
I've tried to play with WGDC but the dip between 3000-4000 rpm is still there. I will try to give 1-2 more degrees of timing in that area (AFR is already good and smooth, and there's not any knock so maybe I have some margin).
Last chance will be MIVEC, but I don't feel experienced enough to play with it.

To be honest, I've also another (smaller) dip at around 5300 rpm: in that area, I cannot do nothing with WGDC since they are already at 100%. I will try also there to improve timing.

Any suggestion is appreciated!

 

I have smoothed the curve out by lowering WGDC in the RPM where boost spike starts and a bit before it starts (from 100% to about 70%) and the dip has gone.

The highest load is now not as spike in 3000 rpm, but increases smoothly up to 4200 RPM.

 

I think I will do the same: I will give up some load at 3000-3300 rpm, but I will have a smoother load curve.

Do you have also a dip at around 5400 rpm? After the boost peak (4200 rpm), my load drops and has a minimum at 5400 rpm, then raises again at 5800 rpm, and finally goes down smoothly up to top.

 

Here is your explanation... https://www.evolutionm.net/forums/ev...af-tables.html

Bottom of the first post.

 

This is alot of help! Its teaching me more stuff thanks a lot and GL on ur problem

 

Thanks, I did not see that post yet.
It's clear that, in my case, the load drop is related to a boost drop after a peak; in fact, my goal is smoothing the boost (but right now I did not obtain big results playing with the WGDC), then load should smooth consequently.

 

I am pretty certain it is not boost related. My before and after MBC logs still have the load dip. Timing makes very little difference, if any at all. It has to be in the flow tables.

 

see frost's reply and link to tephra's thread above.

it is "related" to boost in the context that once max pressure is achieved, it has nowhere to go but down. I guess the real questions are:
1- why does it happen so dramatically?
2- what is the best approach to "tune around" it?

1 is somewhat irrelevant, because of the answer to 2: in a nutshell, we tune our fuel/timing on x,y pairs (rpm,load) as long as the same x,y pair does not appear in two places in the curve (it doesn't since RPM is always increasing regardless of load), you can easily tune around it as long as you know the data point! sure the maps may not look as "pretty", but the end result is the same.

case in point: a properly tuned car on a dyno could show this load dip, but the power/torque band will be smooth. I think a lot of us have it drilled into our head that load is directly proportional to HP in a linear fashion. while this is "mostly true", this minor oscillation in load is an exception to that rule of thumb in a properly tuned car.

hth!

 

Sorry, I should have clarified, it isn't boost control related.

 

No, my only problem was high load oscilation in the 3-4k RPM.

do you have both selenoids at 100% between the maximums?

 

So I spent 2 days playing with target load/WGDC tables and yes - the dip can be cleared this way.


It takes a lot of time doing logged WOT pulls, analysing the logs, changing maps and round and round.... I was hitting max 250 load/27 psi before, now I get 280 load/26 psi.

The base is lowering WGDC in RPMs before the first maximum occures.