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Date: Wed, 17 Aug 2011 15:22:53 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Dennis Haverlah Fuel System...or any others,
 for that matter.
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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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