SXTune Documentation
Last updated: 7 October 2026
Documentation / Guides

Calibration & Control

Turbo boost control

Set a safe open-loop wastegate duty first, then use target pressure and PI correction for closed-loop control.

Engine safety: establish a safe Base Duty Cycle map before relying on closed-loop boost control. A feedback controller cannot correct an overboost instantaneously.

Recommended calibration sequence

  1. Confirm the boost-control solenoid is wired to the configured PWM output and that its operating frequency is correct.
  2. Temporarily disable closed-loop boost correction.
  3. Calibrate Base Duty Cycle across the intended RPM/load range so boost remains safe everywhere.
  4. Set the desired Target Manifold Pressure map.
  5. Enable closed-loop control and assess tracking and stability.
  6. Only adjust proportional/integral gains when required to correct slow response or oscillation.

Boost Control pages

Calibrate the open-loop base duty first, then the target pressure and finally closed-loop behaviour. The live variables page lets the base and final duty, target, error and controller state be checked together.

Boost Control Base Duty Cycle map.
Boost Control Base Duty Cycle map.
Boost Control Target Pressure map.
Boost Control Target Pressure map.
Boost Control Variables with live target, error and duty-cycle values.
Boost Control Variables with live target, error and duty-cycle values.

Boost control strategy

Boost control is achieved by means of a bleed valve in the turbocharger wastegate controlled by a Pulse Width Modulated (PWM) signal from one of the ECU PWM outputs as selected in ECU configuration.

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This Boost Control page displays values relating to the closed loop boost control strategy and is broken down into:

  1. Boost Solenoid Frequency – The piloting frequency at which the boost control solenoid will be driven in Hz.

  2. TPS Thresh enable boost CLC – the throttle position percentage above which the closed loop boost control strategy becomes active (set to 99.45 to disable closed loop boost control)

  3. Maximum Final Duty Cycle – The maximum boost control solenoid duty cycle percentage

  4. Minimum Final Duty Cycle – The minimum boost control solenoid duty cycle percentage

  5. Boost Integral Loop Timer (ms) – The time base for the boost PI controller integral term

  6. Positive Integrator Clamp (%) – The maximum positive value of the boost PI controller integral term

  7. Negative Integrator Clamp (%) – The maximum negative value of the boost PI controller integral term

  8. RPM Thresh enable boost CLC – the engine speed above which the closed loop boost control strategy becomes active.

  9. MAP thresh enable boost CLC – the MAP sensor value in mBar above which the closed loop boost control strategy becomes active.

  10. Fuel Cut MAP Threshold – the map sensor output in mBar at which fuel delivery will be completely turned off (for engine protection purposes).

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The open loop boost control term is calculated by a map as a function of throttle position and engine speed. This should be calibrated to achieve the target boost level before closed loop boost control is enabled. The target manifold pressure in mBar is calculated from a map also as a function of throttle position and speed.

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The open loop boost control term is calculated by a map as a function of throttle position and engine speed. This should be calibrated to achieve the target boost level before closed loop boost control is enabled. The target manifold pressure in mBar is calculated from a map also as a function of throttle position and speed.