Two basic functions performed by an engine management system (EMS) are to provide a SPARK AT THE RIGHT TIME (IGNITION TIMING) and to meter FUEL IN THE RIGHT QUANTITY (FUEL INJECTION).
ENGINE SPEED from the RPM sensor and ENGINE LOAD from the throttle position sensor or MAP sensor drives the injection and ignition. There are two maps for engine tuning. Fuel map is for injector timings and ignition map is for ignition timings. Also known as serial port tuners or OBD port tuning uses the OBD port to gain access to the maps via an interface. For ECU remapping, one should replace the factory EMS with an after-market EMS. ECU tuning software such as EFILIVE is a great tool with a data logger (datalogger) to increase the performance of an engine.
FUEL INJECTION system has fuel tank, fuel filter, fuel pump, injectors and pressure regulator for fuel return. IGNITION system use intake or temperature sensor to "correct' the air/fuel mixture for different air temperatures since the air density fluctuates when temperature changes. It can also use exhaust gas temperature (EGT) sensor to measure the temperature of the outgoing gases inside the header tube.
APSX WIDEBAND also provides the fuel options from lambda to AFR. Such as gasoline (A), lambda (L), E85 (E), diesel (d) and methanol (n). The user can change the fuel type anytime by using the gauge button at the back side as hidden under plastic tab. Just push your finger on the tab and sense the button clicking.