Hi Steve,

 

My personal experience was (and has been over the past 10 years) that IF your header tank is “air tight” then the fuel injected from the header tank into the engine creates a pressure differential that is sufficient to pull fuel at least 24” vertical while “sucking” a heavy plastic marine fuel tank almost flat (because I forgot to open the vent).   While its not the pumps directly – they simply push fuel to the injectors – and hopefully remain fuel saturated – its actually the pressure differential in the header tank this causes that pulls the fuel from the tank.  You could argue I’m splitting hairs but I think it makes a difference whether the pump is trying to suck uphill directly or it’s the header tanks pressure differential.

 

However, I would hesitate to eliminate a boost/transfer pump for the simply reason it would not take much of an air leak to lose that suction from the header tank and without a boost pump ( or gravity feed), there just might be difficulty getting sufficient fuel to the engine to keep it running.

 

In my assessment an inexpensive Facet type 6 psi pump (Sold by Van’s aircraft) is well worth the insurance it provides.  Also as I indicated - it provide sufficient pressure way back when to suppress fuel percolation.

 

I always believe that what may be good for me or you depends on our assessment of the risk involved and your risk tolerance profile. 

 

 

Thanks Ed

The header tank in a Glasair is immediately behind the firewall (Insulated) and glassed into the fuse upper section immediately ahead of the windshield.
The header is approx 24” above the main wing tank.
Are you suggesting then that if the header has no air leaks then the main pump suction could be used to draw fuel from main wing tank up into header and delete the transfer pump?

Steve Izett


On 6/10/09 6:18 PM, "Ed Anderson" <eanderson@carolina.rr.com> wrote:

I don’t really know, Steve.   I do have a fiberglass box around the header tank and pumps/filters with aluminum tape wrapped over it to shield from radiate heat.  I also have a blast tube funneling air into the box.  
 
Early on during test phase when running auto fuel and doing power on stalls (high power, low airflow), I notice the fuel pressure fluctuating and turned on the 6 psi boost pump which eliminated the symptoms.  I then installed the box and blast tube and have had no more such symptoms.
 
In hind sight, putting the header tank someplace other than forward of the firewall would undoubtedly been a better plan.
The pressure differential with just the EFI fuel pumps is sufficient to pull fuel up a 2 foot height and collapsed a heavy plastic marine fuel tank when I once forgot to open it’s vent during the phase I had the engine on a test stand.  So the pressure differential is sufficient.  The only thing that would cause a problem is a air leak in the header tank, then I would be forced to use the boost pump to keep fuel flowing to land as the pressure differential would be lost/weakened.
 
Ed
 
 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of stevei@carey.asn.au
Sent: Monday, October 05, 2009 9:36 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Fuel System

Thanks Ed
How hot does fuel get as it gets pumped then through a hot engine cowl? The lines are insulated under the cowl. How much heat do the pressure pumps introduce?

Steve Izett


On 6/10/09 9:03 AM, "Ed Anderson" <eanderson@carolina.rr.com> wrote:
Hi Steve,
 
Just for comparison -my fuel system is very similar in concept.  The principal conceptual difference is I have a header tank for return of my fuel from injectors mounted on the fire wall and is ½ pint in capacity.  The theory is not much fuel to have to get rid of if it gets hot. The fuel flow into the engine through the injectors continuously pulls cool fuel from wing tanks.
 
 8 gallons of hot fuel (if it ever got hot) might take a while to burn down to the point the cool incoming fuel does some good.
 
This size  goes counter to “tradition” on size of header tanks but is more in line with the “returnless” systems on most of today’s automobiles.
 
FWIW
 
Ed
 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com <http://www.andersonee.com>

http://www.dmack.net/mazda/index.html <http://www.dmack.net/mazda/index.html>

http://www.flyrotary.com/

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of stevei@carey.asn.au
Sent: Monday, October 05, 2009 7:35 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Fuel System

Hi All

We are trying to make a decision re: fuel system.
I’ve attached a PDF with design and questions etc.
Could you please pull it to pieces, make recommendations?
Steve Thomas can you comment also from the GSIIRG perspective?

Thanks

Steve Izett
Perth Western Australia
Building Glasair SIIRG Renesis 4 Port RD1C EC2 EM3

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