Calculating Fuel Pressure Gradient
Figuring out your Fuel Pressure Sensor’s Gradient is a pretty simple task. First you need to determine the operating voltage range for the sensor. While you would expect sensors to go from 0v at the bottom, most will actually start at a higher voltage like .5v in order for the ECU to see a minimum voltage level and be able to detect faults like wiring or sensor issues. For the sake of making things easy we’ll use some pretty standard voltage levels and say our sensor operates from 0.5v-4.5v.
MAKE SURE TO USE THE APPROPRIATE VALUES FOR THE SENSOR YOU USE.
Range = Highest Output Voltage – Lowest Output Voltage
Once we know the range of the operation we need to see how wide it is, so you’ll subtract the high pressure voltage from the low pressure voltage, so in our example sweep of 0.5v-4.5v we have an overall range of 4 volts.
Next we need to convert our pressure from PSI into KPA so our ECU knows how to handle the values. Many common sensors operate at 100psi or 150psi but this would apply for any operating pressures. For the sake of keeping things easy we’ll assume a 100psi sensor is being used. You can use any sort of conversion on the web, the table below, or just multiply the pressure in PSI by 6.89476 in order to convert into KPA (Kilopascals) so at 100psi we have 689.476kpa.
Now that we have our pressure in KPA and our voltage range, we simply divide the pressure range by the voltage range to get our gradient. So
Gradient: Pressure (kpa) / Range (Voltage) =Gradient in KPA/V
Or in our example: 689.476KPA / 4v = 172.369 KPA/V