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Hi
I am running a Rotax 912iS engine on an iEFIS system. The Rotax fuel pressure regulator is regulating the pressure relative to the air pressure in the airbox, and keeps a 3 bar pressure difference between fuel and air pressures.
Since I could not allocate an adequate and reasonably priced differential pressure sensor, I want to display in the iEFIS screen, the pressure difference between direct fuel pressure measurement and the airbox pressure.
The fuel pressure sensor is connected to the RDAC CAN for 912, and the airbox pressure I get from the Rotax ECU via CAN bus.
Is there an option to display the difference between these tow values on the iEFIS screen? Does the screen designer support this option?
Please advise
No that does not exist.
But you do have barometric pressure (i.e. actual ambient pressure at your static port). Your fuel pressure sender would either be a type tat gives absolute pressure relative to vaccum (in which case you can subtract the barometric pressure to get the differential). or if it is a gauge type sender then you get the differential pressure anyway (pretty close to the airbox pressure).
It's all you really need from a diagnostics point of view.
The engine is fairly tolerant of actual fuel pressure - it uses the lambda sensor to adjust injector opening times.
The airbox air pressure is similar to manifold pressure in other engines and the pressure in the airbox can be approximately 0.5 bar at idle and 1 bar at wide open throttle. This difference of 0.5 bar is greater then the allowed Rotax tolerance of 0.2 bar.
In some data analysis software I worked with, I had a simple option to define a new variable which was a result of a formula using some basic variables.
any other ideas, apart from displaying the manifold pressure next to the fuel pressure on the screen?
Given that the Rotax 921is and 915 are becoming more and more widespread, and since it looks like a simple enough addition, it would be a good idea to incorporate internally this capability to calculate differential pressure, instead of making people run additional tubing to the manifold, or buying differential pressure sensors.
