Open Loop Tuning

Open Loop Tuning

The Open Loop table allows boost to be increased over the standard boost that the turbo and wastegate combination provides. The turbo wastegate solenoid will only activate when it sees positive manifold pressure.

To setup the Open Loop table, it will be necessary to repeat several trial and error runs to ensure safe boost conditions. Use the following steps as a guide to setting up your Open Loop table:

  • Always start with small duty cycle settings and increase until the desired boost level is reached. Start with a flat map (same duty at all loads and speeds) at low duty settings and drive the car noting any increase in boost level.

  • Watch your A/F ratios very carefully when increasing boost for the first time as this part of the map will not have been tested if this engine has not been mapped at this boost level.

  • You can setup a flat map easily by selecting all the necessary cells, then typing in the duty value. Make sure you run the engine at the engine load and RPM at which maximum boost is typically reached. This is usually in the mid range of the RPM range of the engine.

  • Adjust the duty of all the cells of the table if necessary - increasing duty to increase boost, decreasing duty to decrease boost - and apply load to the engine to check the resulting boost level. Again, make sure that your fuel maps are adjusted to ensure safe A/F ratios at every step. Repeat until the desired maximum boost is reached.

  • Now that you have set the Open Loop table to achieve the maximum desired boost at the peak operating range, you can increase the duty cycle at all engine speeds and loads at which the boost pressure is below the desired maximum boost. This will help the engine reach its desired boost pressure quicker. This will alter the fuel requirements at these engine loads and speeds so watch your A/F ratios carefully and adjust your fuel maps to compensate if required.

  • Similarly, if a lower target boost is required at certain operating ranges of the engine, such as high RPM where injectors may be near 100% duty, it may be necessary to lower the duty at those points to reduce boost levels.

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