Engine Management systems are used where standard tuning is no longer viable. Most cars can be tuned for minor modifications, but extensive conversions may require different sensors or aftermarket parts that are not compatible with the standard ECU. Some Japanese car upgrades require aftermarket ECU's because the standard management systems will revert back to factory specifications once tuned. The aftermarket ECU's take over from the current ECU and allow extensive tuning to take place. With an aftermarket ECU any modification can be done and tuned for with no limitations.
The stand alone EMS controls all of the engines vital functions and usually comes with features that were not originally programmed into the ECU.
Ignition and fuelling control
Boost per rpm control
Flex fuel capable – ie ethanol or race fuels
Individual cylinder trim
Lamda or AFR tables
Uses factory or aftermarket sensors IE: map sensor
Direct coil control
WOT Shifting (wide open throttle)
Logging ability via laptop interface
Water methanol injection control
Soft limp mode – the car will go into protection mode if it detects a problem
Knock protection – soft limp mode
Boost level protection
How does an EMS work?
An EMS is programmed or mapped to act a certain way under certain circumstances. It will take into account the airflow via Map sensor (boost level), Air fuel ratio via 02 sensors(AFR over RPM/Throttle), oil temperature, coolant temperature, knock sensors, Throttle position sensors, Cylinder head temperature, as well as other inputs and it will in turn control the following via a pre determined map or plan:
Braking systems (traction control)
An EMS can be programmed using the developers software. Map tables can be seen as 3D renders. All functions and features are accessed through the software.