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Date: Mon, 30 May 2005 12:06:15 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: will EFI pumps pump air
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Russell Duffy wrote:

> Will the EFI pump move enough air through it to disturb the fuel rail 
> pressure that's being delivered from the other pump,  
>  I would say yes  
>  
>  
> I'd bet that you have a 50-50 chance of being right :-)   Seriously, 
> I'm not so sure it would pump air well enough to overcome the 43 psi 
> of pressure that the other pump is putting in the rail.  I guess the 
> only way to find out it to do the experiment. I'm not completely sure 
> that's what I want to do anyway. 
>  
> Yep, still trying to figure out how to fix my fuel transfer system.   
>  What's it look like now? 
>  
>  
> Remember the recent caution about copying a system 100%, or it becomes 
> a new system?  Well, guilty as charged.  My system is just like 
> Tracy's, except that I only have one return line to my feed tank.   I 
> plumbed the wimpy facet transfer pump into the same line that returns 
> from the regulator.  That means the facet pump is trying to push 
> against the return flow from the regulator, and it's not doing too well. 
>  
> Even at it's best, on the ground, with no other pumps on, the facet is 
> slow.  In the air, fighting against one EFI pump's return flow, it 
> takes a long long time to see fuel moving.  With both EFI pumps on, I 
> almost wonder if fuel isn't going backwards into the non-feed tank 
> anytime the facet wasn't on because the check ball isn't perfect.  I 
> added a one way valve to stop this, and to stop the fuel from leveling 
> itself between tanks when parked.   
>  
> The obvious solution is to "simply" (NOT) add another hose to the feed 
> tank.  Even if I go through all that hassle, I'm still stuck with the 
> slow rate of transfer of the facet.  It's probably still the best 
> option, but I'm going to investigate every other option before doing 
> this. 
>  
>  Rusty 


One thing I'm considering is to just use the regular pumps to transfer 
fuel. If you plumb the tanks to a fuel selector, then when you select 
the aux side the excess flow will end up in what's now your primary 
tank. This is how some injected Continental engines are plumbed in 
certified a/c. Not my favorite idea, but it does minimize the changes 
from Van's stock system. I've got 2 additional tanks to deal with, so 
I'll have to have a selector somewhere in the system anyway.


If you want to retain the Facet transfer pump system, have you 
considered trying to make a return fitting on your primary tank 
configured like a 'jet pump'? If you feed the engine return in one side 
of the T & the Facet into the bottom, it just might help the Facet 
instead of hurting it. If you can build a plumber's nightmare with the 
return line being a smaller diameter & extending slightly past the 
intersection, it just might work.

I've seen the 1st idea work in certified planes; the 2nd idea is wild 
speculation.

Charlie
(Wish you could have made it up here this weekend; if you get bored & 
need a place to fly come on up for lunch sometime.)