Fuel pressure information
The fuel pressure system calculates:
•Primary/Secondary Fuel Pressure = The differential fuel pressure over the injector. Used to calculate injector flow and dynamic properties.
•Primary/Secondary Fuel Pressure Error = How much the fuel pressure deviates from its target value (error = actual - target).
Two factors affect how the fuel pressure is calculated:
1.Where the injector is mounted.
2.What type of fuel pressure sensor is used.
Injector mounting:
Atmospheric injection: Used when fuel is injected into an area always at barometric pressure (e.g., upstream of throttle bodies, or carbureted-style Throttle Body Injection(TBI) setups).
Manifold injection: Used when fuel is injected into an area where the pressure varies with engine load (intake manifold). This applies to both naturally aspirated and boosted engines.
Fuel Pressure sensor type:
•Vented (gauge): The sensor is vented to atmosphere and reads fuel pressure relative to ambient barometric pressure. With no fuel pressure applied, it reads 0 kPa.
•Absolute (sealed): The sensor reads fuel pressure in absolute pressure, referenced to a perfect vacuum. With no fuel pressure applied, it reads approximately barometric pressure, for example 101.3 kPa at sea level.
•Sealed gauge: A non-vented sensor with a fixed internal reference near atmospheric pressure. It reads approximately 0 kPa at sea-level ambient pressure, but unlike a true vented sensor it does not track barometric changes. At higher altitude, zero fuel pressure may appear as a negative reading. This is a legacy configuration and is not preferred.
Refer to your sensor's datasheet to determine which type it is. Vented sensors are generally preferred because they directly report fuel pressure relative to ambient pressure, which makes setup and interpretation simpler.
Using the correct setting is important for applications that see large elevation changes.
Analog input setup:
Configure the analog input so the channel reports:
•Vented sensor: 0 kPa with zero fuel pressure
•Absolute sensor: approximately ambient barometric pressure with zero fuel pressure applied (e.g., ~101.3 kPa at sea level, ~85 kPa at 1500m elevation)
•Sealed gauge sensor: 0 kPa with zero fuel pressure at sea level. At altitude the readings will be negative. Seal gauge sensor should have a 101.3kPa reference pressure.
Fuel pressure sensor
Fuel pressure reference
Defines how differential fuel pressure is calculated based on injector location (atmospheric or manifold) and sensor type (vented, absolute, or sealed gauge) to ensure correct injector flow compensation.
•Atmospheric injection, vented fuel pressure sensor - Injectors mounted before the throttle, vented fuel pressure sensor. Differential fuel pressure = sensorvalue.
•Atmospheric injection, absolute fuel pressure sensor - Injector mounted before the throttle, absolute fuel pressure sensor. Differential fuel pressure = sensorvalue - BARO.
•Atmospheric injection, sealed gauge fuel pressure sensor - Injectors mounted before the throttle, using a sealed gauge fuel pressure sensor. This is a legacy mode for sensors/signals that read 0 kPa with zero fuel pressure at sea level, but do not track barometric pressure like a true vented sensor. Differential fuel pressure = sensorvalue + 101.3 - BARO.
•Manifold injection, vented fuel pressure sensor - Injectors mounted after the throttle, vented fuel pressure sensor. Differential fuel pressure = sensorvalue + BARO - MAP.
•Manifold injection, absolute fuel pressure sensor - Injectors mounted after the throttle, absolute fuel pressure sensor. Differential fuel pressure = sensorvalue - MAP.
•Manifold injection, sealed gauge fuel pressure sensor - Injectors mounted after the throttle, using a sealed gauge fuel pressure sensor. This is a legacy mode for sensors/signals that read 0 kPa with zero fuel pressure at sea level, but do not track barometric pressure like a true vented sensor. Differential fuel pressure = sensorvalue + 101.3 - MAP.
offset adjustments
Defines an offset adjustment for the differential fuel pressure sensor value.
target pressure
Defines the target differential fuel pressure across the injector(s) in kPa. Example: 300 kPa = 3 bar.
