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I should have added - the best overall approach -
returning hot fuel to the heat-sink tanks and drawing new cooler fuel into the
lines.
Ed
Sent: Saturday, August 13, 2011 6:47 AM
Subject: [FlyRotary] Re: vapor lock
Ok, Finn, that was my guess as
well.
That then brings up a question - my understanding of
"vapor lock" is that it is caused by a low pressure area/combined with hot fuel
on the EFI pump intake which cause the gasoline to flash to vapor - naturally
the EFI pumps can not pump vapor - therefore as fuel is injected from the high
pressure side of the pump (reducing pressure on that side), vapor can form there
as well. In any case, insufficient fuel is injected into the
engine.
Since the injectors are still clicking open, it would seem
that any vapor on that side of the pump already has a chance to vacate the line
(through the injector) - so my assessment is that it is not the relief of
vapor/gas from the high pressure side that remedies the problem, it's removing
the gas from the low pressure side (pump inlet) and thereby permitting liquid
fuel to be pumped that "cures" a vapor lock situation.
So I am puzzled why a gas vent on the high pressure side
would have much (if any) effect on vapor lock. IF there is pressure on the
injector side - I question whether it would be as high as pump pressure - and
even if it were, the injector opening would provide a path for it to be release
- not to mention the pressure regulator. So as I said -I'm a bit puzzled
as to the mechanism that a vent in the high pressure side prevents vapor
lock.
In my opinion, there are two ways to reduce/eliminate the
vapor in the low pressure side - either cool the fuel sufficiently (somewhat
difficult to do) or to increase the pressure in the low pressure line forcing
the vapor back into the liquid - ergo - use a boost pump.
FWIW
Ed
Sent: Saturday, August 13, 2011 2:53 AM
Subject: [FlyRotary] Re: vapor lock
Hi Ed,
I believe it's simply a return to the tank from the
high-pressure side via a very small orifice. How small I do not
know.
Finn
On 8/10/2011 9:28 AM, Ed Anderson wrote:
The one I potential preventive measure/fix I have not
looked into is the vapor by-pass/dump that I know a few folks are using.
I search the archive but could not find a description of this method - anyone
care to provide one?
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