I am building a Cozy MK IV and will install a 3rd gen. 13B. I've spent some
time trying to understand fuel systems for EFI engines, noting that with 2
main tanks, the need for return lines adds a lot of complexity to the
system. I'm thinking about electrically controlled fuel valves on the
firewall (2 valves and 1 solenoid or motor per tank). Since with EFI we
must have electricity to run the engine in the first place, the inability
to switch tanks in case of a power outage is not really an issue. In my
opinion an EFI demands a backup electrical system in any case. I see great
advantages in placing the fuel valves on the firewall:
- shorter fuel lines
- no need for a sump tank
- less fuel heat, because it runs back to the main tanks
- no fuel lines inside the cockpit

There is the added risk of not being able to shut the valves when power
fails due to engine fire. I'm not sure how to address that yet.

My understanding of EFI is rather superficial, so I may be overlooking
things. I may also be overlooking other side effects. What do you think?

Charlie Kuss wrote:

Herbert,
 One very good way to handle the problem of switching the returned fuel back to
the tank it was drawn from is to use an Andair fuel selector valve (U.K.) You can
see the valve I'm referring to at:
http://www.andair.co.uk/
The valve in question is at the lower, left of the home page.
 I would strongly urge you NOT to mount the fuel selector on the firewall. You
could mount it slightly forward of that area to keep fuel lines short and greatly
increase safety. There seems to be a greatly exaggerated fear of fuel
lines/connections in the cockpit area. A properly designed and assembled (I'm
talking double flared, 37 degree lines) system will be very safe.

Charlie Kuss
RV-8 wings
Boca Raton, Fl.

 
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