Fuel Pressure Compensation and Warning Overview

The Pro-M EFI Powertrain Management System can compensate for variations in fuel pressure when used with our High Flow Fuel Pressure Sensor assembly. The assembly will accept up to a -10 fitting, will outflow a -10 line and is intended for use in the feed line, but can be put in a branch and “dead headed” if necessary.

Although not a substitute for a properly designed fuel supply system, even a well-designed fuel supply system will exhibit variations in pressure and even the best fuel supply system is susceptible to component failure and/or a clogged filter. Use of our Fuel Pressure Compensation system will always result in proper fueling, even if the fuel supply system is marginal. Additionally, this sensor allows the Pro-M EFI PCM to warn the driver if the fuel pressure strays outside of an acceptable range.

The real beauty of this system is that it references both fuel rail pressure and manifold vacuum. This is important because this allows the sensor to report a value known as PSID, rather than just fuel rail pressure in PSI. Why is this important? Because fuel rail pressure has no meaning in engine management. All that matters is the differential pressure across the fuel injectors. The differential pressure is the difference in pressure between the fuel rails and the pressure (or vacuum) in the intake manifold. When the Pro-M EFI PCM has a value for PSID, it can use this value to adjust the pulse width sent to the fuel injectors to compensate for variances in the PSID. This allows for more precise fuel control and tighter fuel trim corrections.

Programing the Pro-M EFI PCM for the fuel pressure sensor requires two simple changes to the calibration:

First, change the “FRP_HP” to “FRP Present”. This is shown below.


Fuel Pressure Compensation Configuration


Second, change the “Inj_Compensation_Enable” to “Enabled”. This is shown below.


Pro-M EFI Injector Compensation Configuration


The addition of the Fuel Pressure Sensor, and the calibration steps outlined above, will automatically enable the Fuel Pressure Warning feature. The check engine light will be illuminated, and a fault code will be present should the fuel pressure stray outside of an acceptable range.

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