Boost control

Algorithm

The boost controller is a fairly simple closed loop PID controller with a feed-forward map.

Overboost

The overboost functionality is rather simple - for the time the conditions are met the pedal axis of of the target boost/base duty maps simply gets a fixed number added to it.
I don't recommend using this, and it is not included in the xdf either. To avoid it, simply always map the last two pedal positions (87/112) the same, or rescale the axis.

Maps

• MAP Target - Target absolute pressure in kpa.
  
• Base WGDC - Feed-forward map. In steady-state conditions it should contain the duty cycle, that is needed to reach the target boost. The output of this map is in N75_REQ. Simply alter it so, that N75 and N75_REQ are as close together as possible, apart from the low rpm areas where you have to let the PID controller do it's job.
• P, I, D term - they are what they say.
• MAP signal too low diagnosis - If you are WOT for a certain amount of time and the MAP value does not exceed this parameter, it will throw a MAP sensor signal fault.
• MAP limit - this is the soft boost cut limit. If it is exceeded, N75 will be set to 0 and a fault will be logged.
• N75 upper/lower limit - min/max WGDC output.
• Correction maps - IAT, pATM (atmospheric pressure) - corrects the target boost pressure as a factory based on RPM, IAT, Atmospheric pressure. There are a few variants, some of them are used based on coding plugs.