Closed loop boost target

[434josh]

When setting closed loop targets in psi is there a way to make it MGP PSI instead of psi so I don't have to add 14 psi to the target to account for atmospheric pressure? 

 

[Adamw]

In the G4+ boost control was locked to MAP, this is becuase generally the aim of boost control is to keep cylinder pressure constant.  You generally tune to a acheive a cylinder pressure that the engine can safely handle.  If you use MGP for boost control then the cylinder pressure will vary with baro, this means anything related to cylinder pressure will vary - engine power, suspectibility to knock, etc.

In G4+ this has been opened up to allow other control strategies such as pre-throttle pressure but its still recommended to use MAP in general.  

[INSW20]

With a closed loop boost target, would it be reasonable to set higher DC at lower RPM to help with spool and torque production?  Something like this:

 

Or is this not really necessary due to the Stage1 DC %?

Is there any preference for Base DC Mode to be Stage 2 vs Stage 2-3?

[Adamw]

Stage 1 handles the spool.  

Base DC mode generally depends on how much the DC needs to change as RPM increases to keep boost on target.  Since you have a flat 54% across all RPM's above 3500 stage 2 mode would probably work well for you.  If you had say 54% at 3500RPM but 65% at 6000RPM like is more typical then you would want to use stage 2-3 mode so the base DC follows what is in the table.

[INSW20]

Here was a dyno pull in open loop, if that helps explain my question about Base DC mode.  Thank you!

[Adamw]

Did this statement not answer the question?

1 hour ago, Adamw said:

Since you have a flat 54% across all RPM's above 3500 stage 2 mode would probably work well for you.

[INSW20]

2 minutes ago, Adamw said:

Did this statement not answer the question?

Yes, it did, just thought it would be helpful to see the boost curve vs DC. =)

[INSW20]

For this type of overshoot on a 3-4 gearshift, does this seem more like a P or D issue?  Activation issue?

Stage 2 on - 5.5psi

Stage 3 on - 2.2psi

P - 5.0

I - 0

D - 0.8

Base DC is about 29-30%, minus the IAT trim.  From the descriptions it seems like increasing D or decreasing P would have very similar effects.  Some overshoot isn't that big of a deal, since my highest target boost is 20psi, and it's tuned up to 22psi, but if I can even it out a little bit, I'd like to.  In 3rd gear I ramped into the throttle more slowly than the gear change.

[Adamw]

Would really need to see the log, but most likely a lot more D.  Derivative has the effect of "putting on the brakes" as boost races towards target.   

[INSW20]

 

Here's the zipped log (original was 15MB).  A lot of this was interstate cruising to and from a cars and coffee.  The 3rd/4th gear pull is right about in the middle of the log, the only place in this file that I went 100% TPS.  I appreciate the input!

[Adamw]

Yeah I would try more D.  Generally start with a big change such as doubling the current value so you can get a feel if it is helping or not.