Charlie,
This morning I did some simple tests with the floscan sensor I have on my engine stand. This fuel system uses a stock fuel pressure regulator and a return to the tank taken before the floscan and the injectors. The injectors
are normally dead ended as is common in present automotive systems. For the tests, I installed an adjustable valve and second return after the injectors to simulate fuel flow through the injectors. The attached image shows two orientations that were tested. Changing
from the normal to the angled and rotated position showed a decrease in fuel flow reading of 2 to 4% at flow rates of 11.7 and 1.10 gal/hr. This could probably be taken care of in the calibration of a system. At both flow rates, I also introduced air into
the lines and there was no indication of air elimination being a problem. These results are for a steady flow through the floscan, not a pulsed flow as would be the case when the injectors are in operation, but I have not seen any indication that this makes
a significant difference.
In my plane, I used steel fuel lines from the RX7 donor car to replace the rubber fuel lines on the engine. These have an ID of 0.26". This fuel system uses fuel pumps purchased from Tracy, a stock fuel pressure regulator and
return after the injectors, and a duplex fuel selector valve. The return to one tank is AN6 aluminum line from the valve emptying into the root rib of the fuel tank. The return to the other tank is AN6 to the root rib of the tank and AN4 from there to the
normal vent location near the fuel filler cap. While I did not use AN4 lines to feed the engine, there has been no difference in the performance of these two returns that I have noticed.
Steve Boese
RV6A, 1986 13B NA, RD1A, EC2
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Charlie England [ceengland@bellsouth.net]
Sent: Saturday, June 25, 2011 8:14 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Floscan orientation, fuel line size
OK, 2 questions.
1. For those using Floscan fuel flow transducers:
Anyone have a floscan 201 sensor that's working ok while mounted in other than a horizontal position? My most convenient location would have the fuel path flowing up at a 45 degree angle. In addition, the mounting can have the wires 'up', but mounting would
be a bit more convenient with the wires pointing horizontally.
2. While researching Q1, I found a note from the guy who makes Airflow Performance fuel injection systems for Lycs (they run at around 15-30 psi), recommending 1/4" (AN-4) fuel lines firewall forward to minimize fuel heating & vapor lock. I've already been
tempted to consider this instead of -6 (saves weight, running lines is easier, etc) because the injection pumps & automotive systems use small diameter lines, but was reluctant to go against 'convention'. Has anyone who's flying an injected rotary used -4
fuel lines to feed the engine?
Thanks,
Charlie