On 912iS, have installed two fuel pressure senders/measurement to two aircraft that did not have fuel pressure on panel. I determined that I wanted to install the fuel pressure BEFORE the fine filter so I can measure the condition of the filter itself AND the pressure of each fuel pump and combination. After you get the regulated fuel pressure 40 PSI after the fine fuel filter.
With the fuel pressure before the fine filter, I get a reading of about 70 PSI with new fine filter. When the reading goes to 80 PSI, that is when I change the filter.
Thinking about changing the reading of my Sling 2 to read the pressure before the fine filter rather than after.
The Rotax 912iS installation manual 73-00-00 page 3 through 5 allows the manufacturer to make the decision as to where the fuel pressure sensor can be located.
Here are my thoughts as to what the advantages of fuel pressure readings before or after fine filter:
Advantages of fuel pressure before fine filter:
· Lets you know if the fine filter is ready to change with an increase in pressure.
· Allows you to measure the pressure/health of each fuel pump and both on (I have noticed that there is very little difference wit one verses two fuel pumps on)
Advantages of fuel pressure after the filter:
· Direct measurement of the fuel pressure to the fuel injectors (40 PSI) so if a failure of the mechanical pressure relief valve (low or high pressure) you would know it (even though that would not help the engine failure/problem besides knowing what is wrong with the direct fuel pressure)
Would have to think it out, but IF the pressure relief valve failed to a lower pressure, significantly below 40 PSI or significantly above 40 PSI, not sure what the fuel pressure would read before the fuel filter based on flow/back pressure, etc….
Any way, are there any additional advantages/disadvantages thoughts on best place for fuel pressure sender/reading?
