Closed loop boost DC table query

[CamB]

I have a question on how the closed loop algorithm uses the boost target and DC table. I understand the expectation is that it takes the target kpa from the target table and looks up a base DC % from the DC table by reference to Boost Target on the Y axis (typically). This is as set out in the help file.

If one was to set up a boost target table with TPS vs RPM, would it be preferable to:

1) go through and work out full throttle DC % and build the DC table on the "normal" basis described above; or

2) build a DC table on the basis of TPS vs RPM to match the desired kpa in the boost target table?

Option 1 would (I think) look up incorrect DC % at less than full throttle? It seems to me that option (2) would better match base DC to the boost target required by a given TPS and RPM. But I am concerned that it isn't following the instructions (ie, does the algorithm need Boost Target as an axis)? 

Thanks!

[Brad Burnett]

I usually build the target boost table with rpm on the x axis and tps on the y.

Then I build the wastegate DC table with rpm on the x axis and target boost on the y.

[CamB]

Thanks Brad - and I presume it works fine.

I'm still hoping to understand what it would do under Option 2, so hopefully Link can get back to me.

It would be helpful to know how frequently the PID starts again by going back to the Base DC table. Eg, if the boost target changes because I back off the throttle, does it stick with PID to try and get there or does it start the algorithm again due to the target change.

[CamB]

Have relooked at the help file and it appears to effectively continuously adjust? Suggests the fancier the boost strategy (eg by TPS) the more important an accurate base DC is?

Stage 2
Stage 2 becomes active once boost pressure comes within a certain range of the target pressure (set using
the Stage 2 ON setting). Stage 2 is the first stage of closed loop control. Stage 2 uses proportional and rate
of change (P and D) control along with a base duty cycle table. The purpose of this stage is to control the
approach to the Boost Target pressure. The duty cycle applied to the wastegate solenoid is the duty cycle
from the base table plus the duty cycle from the PD controller. This stage remains active until Stage 3
becomes active.

[Simon]

Had a bit of a discussion and either option would work. The negative to option 2 would be that if you change the boost target table you would then also have to change the base duty table.

The tuners out there would likely have more knowledge on what works well in the real world applications.

[CamB]

Thanks - I thought that might be the case. If I remember (and finally get the thing going) I will report back with anything I find.

The reason for considering it is I am thinking:

- Boost table 1 is low boost, tps vs rpm

- Boost table 2 is high boost, tps vs rpm

- Rotary switch input drives "Interpolate between" table.