snipped

Considering the Cont FI system and the fact that automotive
systems don't need to run return lines to the fuel tanks for hot
fuel. Why do XA systems need to return hot fuel.

snipped

You might get away with moving the pressure regulator to the
tank in an aircraft system. In that case the return line would be short
or non-existent.  A pressure regulator by nature is a three port device.
I am not sure why they put it up next to the engine.
Perhaps for throttle response reasons.

With a computer you might be able to pulse width modulate the pump so
it put out only the pressure and volume needed. You would need a
pressure sensor of course. Might work in an aircraft with simpler
dynamics. Most people have their hands full just getting the engine
installed properly.

Charlie Kuss wrote:

OK
 What am I missing here, on the first statement above??? All the port fuel injected
auto engines "I" work on, have fuel return lines. The fuel pressure regulator is
mounted to the fuel injector rail (RX-7s fall into this category) and the return
line starts at the regulator and goes back to the tank from there.

 Most auto electric fuel pumps will generate in excess of 100 psi. How do you
expect to maintain 40-60 psi, if you don't return the excess fuel???
Charlie Kuss
RV-8 riveting wing main skins on
Boca Raton, Fl.

The idea is you put a tee in the line back at the tank right after the
pump so the line going forward to the engine is 40-60 psi.

I think George is setting us up on this Charlie. :-) Here is a page from
the Bosche handbook. Cute George :-)

Paul Lamar
 
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