Re: Changing 165 fuel delivery

["Bruce Plecan" <nacelp@bright.net>]

Big difference with the pump shutting off.  That's the first application
where I've heard of a float contolled set up, on EFI, I'd mount a pressure
sensor instead of the float and that would seem like a real good idea for
autos.
Grumpy

> >... There's a high
> >pressure in tank pump mounted in the reservoir to pressurize the
> >rails, and fuel is circulated through a GM efi filter, through the
> >rails, and back into the reservoir.  The reservoir is sealed, except
> >for one vent line which could be connected to a charcoal canister.
> >...This means that efi is possible without running return
> >lines to the main tank, ...
> >This reservoir could be used for other conversions too.
>
> Just a cautionary tale... Because experimental aircraft guys hate the
> mess of return fuel plumbing (think of what happens when you have 2-3
> main tanks, ugh), many have tried to do a small sump/reservoir return
> setup similar (sounding anyway) to what you've described above, where
> they pump one-directional from the selected tank with a low pressure
> fuel pump, into the sump/reservoir, and then pressurize the fuel rails
> from there with a high pressure pump which vents excess fuel back to the
> reservoir.
>
> What's been the universal problem with those schemes is the fuel pump
> adds mechanical energy to the gas while it's recirculating it, and
> without the cooling from the larger main tank's surface area, the gas in
> the reservoir gradually heats up, vapor pressure drops, bubbles start to
> become visible in clear fuel lines, and before you know it, things start
> to go to shit.
>
> Now, obviously Merc has this setup working for them, so I don't mean to
> say it's impossible (nothin like an "existence proof", eh?), but I
> mention our experiences in XA rather to suggest that they must be doing
> something quite right, to avoid the problems that have commonly plagued
> us in our applications. IOW, there may be dragons here.
>
> Just me dos centavos, amigo.
>
> Gar
>
>
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