Boost Tuning

Adjusting boost solenoid duty cycle at full throttle

The Boost page helps you tune the open-loop boost control duty cycle table and the target boost table. It shows the relationship between solenoid duty cycle and achieved boost pressure from your logs, then lets you adjust the tables so the engine hits its target boost curve.

Boost Tuning page showing scatter of logged boost data by RPM and the blue target boost line

What the page shows

Only full-throttle data is used on this page (TPS above the threshold defined in Settings, default 80 %). This focuses the analysis on the conditions where boost control is most critical.

Tabs

The Boost page is split into four tabs:

View Boost Pressure
Scatter of logged RPM vs MAP, coloured by throttle position. The blue line shows your target boost pressure from the boost-target table. Use this tab to spot where the engine is over- or under-shooting target.
Initial Duty Tuning
Scatter of required duty cycle vs RPM, calculated from the difference between logged MAP and target MAP and scaled by the Response Rate setting. The line shows the current open-loop duty table; adjust the table to follow the scatter cluster.
Initial Duty Table
The raw open-loop boost duty cycle table. Edit cells directly with the standard table editing shortcuts (see Keyboard Shortcuts).
Target Boost Table
The boost target table that defines what MAP the boost controller is aiming for at each RPM. Adjustments here drive the blue target line in the other tabs.

How to tune boost duty

  1. Ensure your ECU has a target boost table loaded. The blue target line is derived from this.
  2. Log several full-throttle runs covering the RPM range. It doesn't matter if other data is also in the logs.
  3. Make any desired adjustments to the Target Boost Table.
  4. On the Initial Duty Tuning tab, adjust the duty cycle to match the calculated required-duty scatter. Initial Duty Tuning tab showing required duty cycle data points
  5. Click Update to commit, save the file and load it to the ECU, then collect another log to verify.

Relevant settings

SettingDefaultDescription
Boost Control Minimum TPS80 %Below this throttle position, data is excluded from the boost page.
Boost Control Full Throttle Req. Time1.0 sMinimum duration the throttle must be above the threshold before a data point counts.
Boost Control Response Rate1.0 kPa/%Expected MAP change per unit of duty cycle change. Used to scale suggested corrections.
Boost Control Maximum Error30 kPaData points further than this from the target boost are excluded as outliers.
100% Duty Boost Multiplier2.5×Relative boost expected at 100% vs 0% duty. Defines the response curve shape.

See Settings Reference to adjust these.

Note — Two boost tables (ME) ME calibrations include two boost duty tables (BoostOL1 and BoostOL2) and two target tables (BoostTarget1 and BoostTarget2), corresponding to different boost maps (e.g. low/high boost modes). DigiTune GTS edits both, with the currently active table displayed based on the calibration's boost map selection.