RaceROM Custom Map Integral Output Timers


Timer creation in custom maps

A timer map can be used for such things as Port Injector purge for Ethanol sensor, cold start injector adjustment or intercooler water spray using the CPC solenoid valve.

In this example we will make a timer map that could be used to purge the port injectors of a BRZ/FRS when the flex fuel sensor is installed in the PI fuel supply line.

How to set this up

Create a custom map, setting the Map to activate when the engine speed is above 500RPM, however, it could start using any variable. To ensure the timer only runs once check the “initially inactive, once activate remain active until key off”. Be sure to enable the Map in the modes that E85 would be used in.

Use the Min, Initial and Max values to control how far the counter will count. Set the output channel of the map to calculation only and the Output Function to “add map output to integral, Add integral to channel value”.


Next fill the map with a value for integration. The value will depend on the ECU’s processing speed (0.05 was close to 1sec on our BRZ). Reduce these values to make the timer run slower.

Use a second custom map, set to be active between the desired timer values (e.g. 1 to 120 timer counts). Which would give approximately 120sec of PI fuel line purging. The thresholds must be between 1 and the maximum value otherwise the map will always be active.


When active it can be setup to modify any available parameter, set it to add the map value to the Fuel Injection ratio to purge PI the fuel line for a PI mounted ethanol sensor. But only add values at low RPM and engine load.

To set up the PI purge, set values in a custom map to add the map value to the fuel injection ratio between the desired timer counts. We only needed to do this at low RPM and light load so these are used as the map axis.


Please note only the DI is used at idle (the ECU ignores PIDI ratio maps) so to purge the line you will need to hold the RPM above idle for this map be active. This could be done automatically using another custom map activated using the options but set the output as Accelerator Pedal % and use output as minimum filling the map with 7 values at low RPM and load.

When the map adds the desired value it makes the PI run full time and purges the fuel line. See the logged data below showing the switch from 100%DI to 100% PI, for approximately 120sec.