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When Mazda put out the early cars RX2 and RX3 they had a return line in the main fuel line that ran past the carb and back to the tank. This kept the carb supplied with the coolest fuel in any condition. The actual fuel pressure was about a pound. Worked great. Until you raced the car then the 2 piece spring loaded needle would let the engine flood when the car was side loaded.

Radiant energy from all of the exhaust system can heat anything it can "SEE". Any straight line from any exhaust piece to anything you wanted

kept cool will defeat you. It is easier to shield the exhaust parts than doing everything else. An air supply to the exhaust shielding to urge the heat out of the cowl is all that is left. Mr, Murphy, my science teacher had a glass water jug he had removed most of the air from, but left behind about 3 inches of water.

If you held your hands on the sides of the jug, the water would boil. There is your vapor lock. Heat and low pressure. Presto. Works every time. Pumps lower than the tank where possible. Fuel and fuel lines as cool as possible.

Lynn E. Hanover

-----Original Message-----
From: Ernest Christley <echristley@att.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, Aug 17, 2011 4:23 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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