BTW, are you about ready to fly the Rocket again?
Not sure how your non-return system is plumbed.
OK it all makes sense. I really think vapor lock or boiling fuel is what knocked me out of the air last year and I really do not want to go through that again..
A couple of Murphy Moose operators have teed off the engine driven fuel pump thru a number 30 drilled orifice into an inverted metal gascolator the back to the tanks. Does this sound like a reasonable thing to do? (bearing in mind it is a pressure carb or single point FI not multiport FI)
Milt: I'd do exactly what Don described but I'd also add a placard.."Use left tank for 30 MIN first before switching to right tank" or similar , in order to make room for the returned fuel. In the future, someone else may own the airplane and it may also serve as a reminder to you that if this instruction is not followed, your fuel will be going overboard (fire?) if it's returned to the left tank and your range will be miscalculated as well.
Regards,
Spent several hours on the phone yesterday 1st with the M14 importer then Don at AFP and derived much good and interesting info.
It appears in the last 2 years 5 or 6 M14 powered aircraft (including mine) have gone down due to un explained power loss. The one thing they all had in common was no return line.
After talking to Don and the importer I am convinced the line is essential mainly to provide added fuel flow for cooling of the pump and lines and to decrease the amount of time fuel spends in a hot environment.
My particular installation has only one tank which is the entire leading edge of the one piece wing and the 6" aft of the spar.
So based on Dons advice I am going to run a return line from the pump to a tee and then through 2 .0150 orifices out to each wing tip so as not to get an imbalance. While it is one contigous tank there are several baffles to keep fuel shift to a minimum and I suspect return to only one side will give me a heavy wing.
thanks for all the input.
Hey Milt, I think you need to rethink this a bit.
Don's post mentioned a .030" return orifice.
You are now talking about two .015" orifices--------half of the size Don mentioned.
Seems logical-----two holes half the size should be equal to the one larger hole, right??
But, in fact when you double a hole, you get four times the area, and theoretical flow. And the smaller size orifice you are working with, the flow drops even faster due to friction loss, so the 1/4 area actually equals less than 1/4 flow.
You probably need to go to .020" or maybe even a tad bigger if you want to keep the same flow as a single .030" orifice. Sorry, I dont know the exact size, (all my flow charts are for fire hose/nozzles) hopefully one of the engineer types on here can help.
ECI has some detailed directions that include pretty good pictures on how to install the fuel return lines. Their instructions even include a parts list for everything you will need to make it work. As AllenC mentioned, it is not a complicated process as long as the tanks are off the wings. Their design has the return line traveling through the Z-brackets that attach the tank to the spar. It is a clean efficient path that I think will work well with any tank whether quick built or not.ISSUE: I will soon have QB wings with fuel tanks completed. What is the best (assuming feasibility) of adding a fuel injection system fuel return line (vapor lock mitigation)?
I am considering pros and cons of adding a fuel return line for all the reasons discussed in the various links and threads on this topic. My query to Vans brought the response that "you can't add return line to QB tanks." I don't think that is true as I've seen some pretty dramatic aircraft mods over the years and adding a fuel return line seems to rank at the bottom of the tech complexity scale. So I'd like to solicit advice/consel as to not only "how" but if it is necessary with a particular brand of FI.
thanks,
Don