Dear All
I have tried to make sense of this but not knowing what is going on inside the supplied manifold I cant figure out how this works.
Regards,
Anton.
fine filter sub assembly.JPG
Dear All
I have tried to make sense of this but not knowing what is going on inside the supplied manifold I cant figure out how this works.
Regards,
Anton.
fine filter sub assembly.JPG
There is nothing going on inside the manifold except passage ways for fuel to flow. The 180 degree turn after the filter is confusing. Fuel comes from the pump, enters the manifold. From there you see it pressurizes the manifold for which there is a fuel pressure sensor that mounts on top of the manifold. Fuel will flow across that sensor port and through the filter due to less resistance and exit the T-fitting identified by "XG" that feeds the engine. If the fuel filter becomes obstructed, the fuel will bypass the filter through the second route that parallels the fine filter. The fuel turns that 180 turn and out the "XG" fitting to the engine.
Eddie Forward
Flying
SS7, 912iS, Garmin G3X
Dear Eddie
Thank you but it doesn't help. There is a check valve named XD. Surely the valve will stop the flow straight to the engine. This means if the filter gets blocked the whole system is blocked. If the check valve allows flow to the engine, nothing will go through the filter unless the chech valve is limited in flow rate and therefore causes a fuel pressure increase. Am I missing something here?
Last edited by anton.willemse@gmail.com; 05-18-2022 at 01:03 PM.
Just one detail: the check valve doesn't see full fuel system pressure. Since it's connected to both sides of the filter (one side via the manifold and "XC" fittings, and the other side via the "XG" tee and "XH" tubing), it only has to hold against the normal differential pressure drop across the filter. As the filter gets blocked, that differential pressure rises closer to full system pressure, which is more than enough to overcome the valve spring, unseating the valve and allowing the engine to draw unfiltered fuel.
Eric Page
Building: Kitfox 5 Safari | Rotax 912iS | Dynon HDX
Member: EAA Lifetime, AOPA, ALPA
ATP: AMEL | Comm: ASEL, Glider | ATCS: CTO
Map of Landings
Anton, that check valve XD has a spring in it that allows it to open in the "free flow" direction only if the pressure drop across it exceeds 11.8-17.6 psi. If the fine filter clogs enough to exceed this pressure drop, the check will open and keep feeding unfiltered fuel to the engine.
Sorry Eric, didn't see your spot on explanation.
Jim Ott
Portland, OR
Kitfox SS7 flying
Rotax 912ULS
Thank you all. I've seen the light!