1.1.81 boost anytrim bug.

[GintsK]

Hello!
When playing with boost settngs AVP found unexpected boost fluctuations. Caused by unstable boost target. and unstable boost target is caused by some failure in boost trim algorithm.

Boost trim should simply change boost target by percentage (mult) or by kpA (additive). But for some reason it is so just below 100KPa of MAP . Above BoostTgt becomes boost dependent. More boost cause less target. In any case when trimming is to positive dirrection. Target is not stable also for trimming to reducing side.   

Here is log file created on little modiefied default config for 1.1.81
   http://www.vems.hu/files/GintsK/v3.3_n003223-2010.11.15-18.41.59.vemslog
   same happens with both: additive and multiplicative boost trimming
Conditions:
Logfile is from bench test.
150% Boosttrim mult applied using Ch7
TPS weight 0,
tps vs boost 100% always.
BoostTgt vs RPM 200KPa always.
Only value changed during log is MAP - simulated using syringe.

In my understanding BoostTgt must be 300KPa (200*150%). But it is not so.
As result it is not possible to use trim for proper boost rising. And when boost rapidly comes to target, taarget itself starts to fluctuate and as result also closed loop boost starts to fluctuate.

Here is example from AVP:
http://www.box.net/shared/aqla66hchu
Problem is around 8:20
Initial target is ~306KPa 110% trim applied ->somewhat as 335KPa expected.

Gints

[Enn]

Hello

Your problem is fixed in Fw 1.1.86
Maybe release in a few day.

http://www.vems.hu/wiki/index.php?page=IssueReports

Norbert

[GintsK]

Thank you!!!

Little related: why anytrim for refDC is excluded? Instead we have two anytrims for boost target (multiplicative, additive) what can be configured do exactly the same. Just with little different anytrim curve shape. 

[lugnuts]

I would also like to see anytrim for just refDC as an option

[lugnuts]

1)
Question about the Boost DC trim.

It is still there under "Inputs - Input Channels" it is called "Boost Open Loop DC Adjust"

The setting is "un-highlighted", I can't get it to become active with any combination of Boost Alternate
or Boost PID settings.

Is this still used?



2)
I was playing with a trim pot on the bench last night with the 1.1.81 anytrim.
What I found was, the trim amount is "correct" if you look one mv row/setting "down" from where you actually are.

Example, I had "-100" set from 0 to 313 ohms, and -50" set at 625, 938 Ohms.
When I set the trim pot at 0, 313, and 625 Ohms, I was getting "-100" boost target trim
With the trim pot set to 938 Ohms, the boost was trimmed to "-50"