Injector pressure – AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual User Manual
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© 2014 AEM Performance Electronics
Infinity User Manual
FI_DutyCycX
Units: %high
Description: This is the duty time. It should be set to 100 for high impedance injectors. This
depends on the particular injectors current for the hold cycle of the injector. 40-60 are generally
acceptable.
Injector Pressure
The fuel calculations in the Infinity ECU take fuel pressure into account as follows:
First the Manifold Pressure is calculated. MAP [psig] is calculated based on the MAP sensor
and the Baro sensor (the baro sensor must be external, since the ECU enclosure is sealed).
Then, the Injector Pressure is calculated. InjPress [psig] is calculated based on the Fuel
Pressure [psig] sensor and the MAP [psig] calculation. In other words, this is the pressure
difference that is measured between the fuel rail (top of the injector) and the intake manifold
(bottom of the injector).
Injector Pressure is used in a simple lookup table to determine InjFlowRate [cc/min]. Injector
Pressure is also used as the y-axis of a simple lookup map to determine InjOffset[us].
InjOffset[us] is the injector response time, latency, offset, dead-time, etc.
If a fuel pressure sensor is not installed, or the fuel pressure voltage is outside the acceptable
voltage range, the Infinity ECU will use a failsafe value for fuel pressure. When performing the
failsafe calculations, the algorithm will check the fuel pressure regulator option (located in
which can tell the ECU that the fuel pressure regulator will be vacuum-referenced
(FuelPressure failsafe will always assume X psi above manifold pressure, InjectorPressure will
be constant) or atmosphere-referenced (FuelPressure failsafe will always assume X psi, and
actual InjectorPressure will be influenced by MAP).
When using staged injection, there is a second set of InjFlowRate and InjOffset tables. Currently,
the Infinity ECU assumes the fuel pressure is the same on both fuel rails.
InjectorOffset
Units: PSIg vs Volts
Description: If a fuel pressure sensor is installed (see
), injector pressure can
be calculated. This is simply the pressure difference between intake manifold and fuel rail
pressure. This table is used to setup the injectors' latency (response time) based on the injector
pressure and battery voltage.
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