Bram Posted November 30, 2016 Report Share Posted November 30, 2016 Hello again. Just another silly question. When calibrating an oil pressure sensor to the Link G4+. Does the ECU use absolute or guage readings? The sensor manufacturer has specified the sensor refferenced to atmospheric pressure. So that means its range is effectively 1-11bar absolute or 0-10bar above barometric pressure. What way of measurement is the ECU looking for? I would assume everything be in absolutes, but it doesnt look right for oil pressure.And I also have a fuel pressure sensor. Fuel pressure sensor is from the same manufacturer (Honeywell) but it is 0-100psi again as a guage reading. Same question as the above, which measurement is the ECU looking for? Im sure this has been covered somewhere before. but i couldnt see it with a quick search. Quote Link to comment Share on other sites More sharing options...
Scott Posted December 1, 2016 Report Share Posted December 1, 2016 The ECU will do oil pressure and fuel pressure in absolute values. If I enter the following calibration into the ECU:And set an Analog Volt channel to MAP (using Cal Table 4) and feed the channel 0.9v I get a reading of 100 kPa.If I then leave the channel at 0.9v and change the function to Oil Pressure using Cal Table 4 I get a reading of 101 kPa.If I then leave the channel at 0.9v and change the function to Fuel Pressure using Cal Table 4 I get a reading of 101 kPa.Scott. Quote Link to comment Share on other sites More sharing options...
Adamw Posted December 1, 2016 Report Share Posted December 1, 2016 Although it may be possible to calibrate your sensors in absolute I cant see why you would ever want to? Assuming this is a car and not a spaceship...If you look at your oil pressure in a log for instance you dont want to be mentally subtracting atmosphere from it every time. You really only need absolute pressure for MAP or EMAP to calculate density, any other pressure measurement I can think of on a car should be gauge pressure. Quote Link to comment Share on other sites More sharing options...
Bram Posted December 1, 2016 Author Report Share Posted December 1, 2016 Although it may be possible to calibrate your sensors in absolute I cant see why you would ever want to? Assuming this is a car and not a spaceship...If you look at your oil pressure in a log for instance you dont want to be mentally subtracting atmosphere from it every time. You really only need absolute pressure for MAP or EMAP to calculate density, any other pressure measurement I can think of on a car should be gauge pressure. Yeah. I totoally get that. As you say there is no need to measure absolute for those 2 parameters. And i dont think id ever see oil or fuel in vacuum either (which my sensors are unable to measure). I just wanted to know which way to set the cal table so the value represented in the ECU matches the actual pressure. For example, IF the ECU did measure fuel/oil in absolute, I would then have to add an approximated 1 atmosphere (101kpa) onto my scaling values listed by by sensor manufacturer. BTW - My car is a spaceship... Quote Link to comment Share on other sites More sharing options...
Adamw Posted December 1, 2016 Report Share Posted December 1, 2016 If you input the calibration points as they are listed on the sensor manufacturers datasheet, the ecu will measure/read/display in gauge pressure. Quote Link to comment Share on other sites More sharing options...
Bram Posted December 1, 2016 Author Report Share Posted December 1, 2016 (edited) Cool. All under control. Both sensors are Honeywell. Fuel is the Stainless steel PX2 0-100psi. And the oil is a brass PX3 0-10bar. Both are refferenced against atmospheric pressure (gauge). Only got the one stainless steel sensor because they are over double the price of the brass models.Calibration for them is easy. Linear 0.5 to 4.5v which equates exactly to the sensors specified range. 0-100psig or 0-10bar. Edited December 1, 2016 by Bram Quote Link to comment Share on other sites More sharing options...
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