The injector on-time is calculated on each synchro based on the total mass of fuel required for this fire. 

The current volume flow rate for the injector is calculated from the nominal calibration (at a set pressure), adjusted for the current operating pressure and fuel temperature.  The injection mass demand is converted to a volume and combined with the injector flow rate to get an injection on-time.  The on-time is then multiplied by the N cylinder corrections and finally the battery voltage opened time correction is added.