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Al Wick wrote:
< I had the issue of a the pressurized lines being
< perfectly sealed.
So, in the future, if you have a bad injector you don't want to know about it? I'd want to be able to smell that fuel leak and replace the defective injector. I would not want to mask it.
If it is leaking enough to make a difference, it'll show up in the EGT and it won't need 55psi to leave enough fuel in the manifold to raise a flag.
-al wick
----- Original Message -----
*From:* Ernest Christley <mailto:echristley@att.net>
*To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
*Sent:* Wednesday, August 17, 2011 8:22 AM
*Subject:* [FlyRotary] Re: Dennis Haverlah Fuel System...or any
others, for that matter.
Al Wick wrote:
> I'm really concerned for some of these fuel designs. The fuel
bleed has
> nothing to do with vapor lock. Virtually no effect at all.
> I don't know why others are doing it, but for me, the bleed has
nothing at all to do with vapor lock. Some
conversations have been mixed together, so I can see how that
could be the impression. The point of the pressure bleed
is to bleed off the pressure after shutdown.
I have a strong, positive head pressure going into my pumps. They, and the regulator, are about 8" directly below the
tank. Excess fuel goes back to the opposite side of the tank from
the pickup, and a single line goes forward to feed
the injectors. The fuel lines are arranged such that heat soaking
the lines to the point of boiling the gas will push
liquid fuel down hill and behind the firewall, isolating the
gaseous gas with its heat at the top of the line. Turning
the pumps on will pressurize the line to 55psi, returning most of
the gaseous fuel back to a liquid state. The ECM is
programmed for a longer clearing pulse on hot start.
The point of the bleed is to allow fuel to move back to the tank. I had the issue of a the pressurized lines being
perfectly sealed. The pressurized fuel was finding the path of
least resistance out, which just happened to be out the
injector and into the intake manifold where it sat as a little
puddle. Heat soaking the lines would not push liquid
fuel downhill and back behind the firewall. It would push more
fuel into the manifold. A puddle of gas sitting in a
composite manifold, just above a hot exhaust stack is just bad
mojo. A poorly sealed regulator allows the pressure to
bleed off in about 5 seconds (give or take), isolating the hot
fuel in front of the firewall, and keeping the rest cool
and out of the intake manifold.
Got nuthin' to do with vapor lock.
--
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