Hi Leon;
Merry Christmas to as well. I'm done with school till next fall, so I can
now get back to concentrating on the fun stuff.

> Maaaaaaaaaaate,  what you are doing scares me witless!!  (Some
> would say that wouldn't be hard!!! ({:>) I've always thought that ya
> wuz supposed to return the  the fuel from the rail back to the main
> tank via a "return line".  Then ya don't need a 'fool koola"
>
As I mentioned on the list (which you've probably read by now), I always
maintain gliding distance to a runway and try to be prepared. Unfortunately
these problems don't always show up during ground runs and cooling
conditions on the ground are drastically different from those in flight, so
I'm trying to work them out in the safest way possible.

> So the way I do it is I have the main EFI pump(s) feeding from the
> bottom of the "header tank"  (aka "surge tank" for us "kharys").
> The low pressure lift pump brings fresh fuel from the main tank and
> dumps it into the header tank low down.
>
> The fuel returniong from the fuel rail is dumped back into the TOP
> of the "surge tank''.  There is then a return line back to the main
> tank.  Obviously hot fuel is less dense than cool fuel,  so it wants
> to stay up high,  and as ffresh cool fuel is supplied by the lift pump,
>  it dispaces the hot stuff back to the main tank..

This is very much like the way I have mine plumbed as well, with the
exception of a return to the mains. I do have a vent line with a shut-off
valve that is connected to my fuel vent header. This allows me to vent
air/vapour when filling the tank. During normal operation this vent line is
closed, so the tank should remain full of fuel. Theoretically I could recirc
fuel back through this system to the tank I am drawing from without
replumbing, as the tank I'm drawing from needs to have equal amount of
air/fuel to replace what is being pumped out to the header tank. Since I
will be consuming some of the fuel that I send to the header tank, the
amount flowing out the vent line will be less than what is required to make
up for what has been pumped out of the mains, so air will still flow in the
vent line to the mains, preventing the header vent from flowing overboard
out the vent line. But I'm not certain I'd trust this completely. Possibly a
small float type check valve in the vent line would prevent fuel from
flowing overboard, allowing only air to flow into the main tanks. This
sounds complicated but may work well. Plumbing in a separate return line
would be best, but would not be easy, as it would require removal of the
wing tanks and opening them up to add another inlet in addition to more
valves to manage the returns.
>
>
> Yair, yair,  yair,   I KNOW it means switching the supply AND the
> return line, (if you have multiple tanks),  but it keeps the fuel cool.
> It also avoids pressure build-up in the header tank.
>
I feel I already have too many fuel valves to manage. I don't find it to
bad, but other pilots seem to be overwhelmed by it. I can imagine that in
the future other pilots will be flying it so I don't want to get too
complicated.

> Another thing - Fuel pumps should NEVER EVER be anywhere
> near an engine or ANY heat source.. A little leak,  a small squirt on
> the hot exhaust and "WHOOOOOOMP". KFA - ("Kentucky Fried
> Aircraft" - or Race car  -  or Ski Boat).  Which is why I have a
> pathalogical aversion to carburettors. seen too many engine fires
> over the last 40 years.   (Ask poor Ken,  he knows!).
>
> Ideally,  EFI fuel pumps should be behind a vapour tight firewall
> separate from the cabin,  well away from any heat source (like a
> turbo or exhaust). Any heat source should be shileded by a
> reflective shield preferably S/S backed by some insulation,  and
> have at least a 5-6 mm air gap..
>
> EFI pumps should ALWAYS be generously ventilated and
> DRAINED to atmosphere..  The prodigious quantities of fuel that an
> un-throttled EFI pump can shift has to be seen to be appreciated.
> Additionally,   all flexible fuel lines should be stainless braided and
> covered with some sort of "fire sheath" material..
>
> You don't get to race out here if you have an electric fuel pump in
> the engine bay or the passenger compartment!!.  They won't even
> let you route fuel lines through the cabin.  You need to keep the
> "burnie -burnie" stuff WELL away from your body,  so if you happen
> to have a prang, and a fuel line splits,  you don't get immolated
> before you egress the area..

Boy, I sure wish that there was an easy way to comply with all of this. Of
course with an aircraft there is so much compromise. I have the boost pumps
located under the console between the seats with the selector valves located
in the console. This allows convenient switching of tanks and allows a
crossover between boost pumps for redundancy, then fuel is fed to the header
which is aft of the top of the firewall. None of this is ideal as it puts it
in the same compartment as I. But at least this keeps it away from the heat
of the engine. The FI pumps and filters are on the cool side of the engine,
away from the exhaust, but of course the injection rail is right above the
intake manifold, which is right above the turbo. Not much can be done about
that.
I've considered moving the FI pumps and filters aft of the FW, but I really
don't want hi-press fuel in the cabin. So I think a shroud with cool air
ventilation is best for this.
I've noticed that in pictures of crashed RV's, the plane crumples and tears
open so that there really isn't a solid separation between engine and pilot,
so keeping fuel out of the cockpit may be a false sense of security. I think
the safest way would be to keep it all in the wings as they are designed to
tear off and go their own way. I did consider this when building, but wasn't
comfortable with the use of solenoid valves to switch fuel, but this would
be lighter, simpler and safer way to accomplish this. Now that I've had
several years of instrumentation experience at work and school, I would
certainly do things different, if I was doing it again.
For now I will attempt to improve on my existing system, but I'm
considering following Rusty's lead and do a "Rev2". Of course I'll still
keep my cowl and turbo :-)

>
> Anyway,  hope all is well.  Would appreciate your comments on
> the above as always.  if you feel that the drivel I have just penned
> has any merit,  feel free to post it on Fly Rotary.
>
> Cheers,
>
> Leon

Thanks Leon, your comments are always appreciated and entertaining. I'll
forward this reply to the list as well.

S. Todd Bartrim
Turbo 13B RV-9Endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

   "Whatever you vividly imagine, Ardently desire, Sincerely believe in,
Enthusiastically act upon, Must inevitably come to pass".