I realize this may not fully answer your question. There can be no standard line size with all the system variables in play.
Since most of the fuel systems we plumb use -6 AN fittings and were originally used with 303 hose (5/16 .312 ID) we use the teflon equivalent. I'll bet Don Rivera has a guideline. Tom
I'm still convinced that the best solution would be a pump in each tank, with one of those sock filters, exactly as done in the auto world.
Check out page E3 here from Parker: https://www.parker.com/literature/H...atalog 4400 PDF Files/Section_E_Technical.pdf
If I were installing EFI, I'd be looking hard at push systems right now. It largely eliminates vapor formation issues, and flow rates can be very high even with -6 line.
I chewed over the idea of pumps in the tanks, but it brought up a few complications. The return fuel would still require a selector valve to make sure it's going to the correct tank. A pump failure leaves you with an unusable tank, unless you put two pumps per side. And switching tanks would be a multi-step process--switch return fuel, switch new side on, switch previous side off. One could possibly rig something up so moving the selector switched the pumps as well, or use a solenoid valve and rig it to a fuel pump switch, but then that leads down a road of more complexity.
In the end, I decided that current EFI practice--duplex valve, dual pumps immediately after the selector, and minimize suction losses before the pump--seems to be working well and I hadn't heard of anyone having issues with that setup. It minimizes fuel management tasks and is close to "standard" operating practice.
If I were installing EFI, I'd be looking hard at push systems right now. It largely eliminates vapor formation issues, and flow rates can be very high even with -6 line.
That particular page doesn't reference the fluid. I think it's valid for hydraulic oil, but probably not avgas. Huge difference in both viscosity and vapor pressure. Not a big deal on the pressure side, but the suction side is another story. All gasoline systems develop vapor bubbles if you suck 'em hard enough, while lube oil has a vapor pressure near zero.
I'd simply avoid using winter blend mogas in the summer or flying above 10,000 on hot days with summer blend mogas. These are a bit scary no matter what fuel system layout and line sizes you use.
Barring a bunch of tight bends or 90 degree fittings before the inlet and having the fuel level no more than 4 inches below the pump inlet, -6 will work on most any RV application running 100LL or summer blend mogas.
I hear you. EFI, dual inline electric pumps. Can you run both pumps at the same time, sucking through the fuel selector and inline filter?
We have many dozens of folks doing just that on 100LL and maybe some doing it on mogas. I'd personally just use one pump at a time with mogas on a warmish day though. That's worked fine for me for a number of years now although I rarely fly when it's over 27C or so.
I'll be doing some fuel system component testing in June on a new project. I'll try to gather some info on flow rates and temperatures and see if I can induce some vapor at the pump inlet using winter gas on a warm day. Would be good to know how much margin we have. I do have a fuel tester from Petersen I can run some samples through to know where we're at.
I?m not sure where you are going with this particular thread...
I have done fuel flow checks with one and both pumps running and there seems to be no adverse effects on the ground. The single pump provides plenty of flow to feed the engine, and both increases that flow about 40%. That tells me that the suction side is working harder with both pumps running....
....so its worth considering that running 2 pumps for takeoff might actually increase your chances of a fuel starvation event? Sure, you are pretty safe from a pump "failure", but does that help you if you pull so hard that you cavitate both on a hot day departure? Not trying to be alarmist - just thinking out loud.
Many people have asked us over the years if they can run both pumps for TO and landing and I've said yes with some caveats (free inlet path, and watch for fuel pressure rise in some cases). Some have asked what I do on my plane and I tell them I just use one pump at a time. I'm not much worried about a pump failure given our long experience with them.
Free flow (pumping to a bucket, so to speak), or pumping back to the tank through the pressure regulator and return system?
A pressure gauge near the inlet to the pumps would tell a lot. Two conditions, engine at idle, WOT at max AOA...
Can anyone suggest (or link) a fuel system design reference listing allowables for tube/hose size vs volume?
I'm not turning up anything with a web search, and I'm starting to think it's all done empirically.