ROTAX 912 UL return line fuel quantity?

I have a RV-12, the return orfice is .02 inches. The fuel flow sensor shows 1.2 GPH flow with the electric fuel pump running at 5 PSI, engine stopped. When calculated the numbers are between 1.1 and 1.3 GPH with fuel pressure 4-6 PSI.

Hi

Thanks for your reply. That is practically very low return, so I believe it can easily be included into parralel flow. 

My aircraft, fitted with Rotax 912ULS, returned a little over 7L/hr to the header tank. Return restrictor jet was a Mikuni #35.

Hi Tadej,

"We believe aux fuel tank would be transferred within 10minutes or so (24l). "

 24 L in 10 minutes = 144L/hr.

What concerns me is the associated fuel pressure.

You will need to be careful that the fuel pressure, developed during transfer, does not overcome the float bowl valves.

Should the float valve be forced open, this may result in reduced engine power/failure, fuel spillage/leak (fire?)

Rotax 912 Operators Manual, 2) Operating Instructions, 2.4 Operating limits - Fuel pressure, Page 4 

 Fuel pressure Max. 0.4 bar (5.8 psi) (0.5 bar (7.26 psi)