HI Bob
I think what Ken is trying to say that if you have any kind of flow allowed
thru the tank, then the ratio of air to gas will increase which could get it
into the combustible area. If you just have ram air effect via the inverted
'L', then you will not have flow, but just the ability to replace the volume
of fuel flowing to the engine.
For example, if you have an 'L' or 'J' tube on your fuel cap plus other vent
holes drilled into the neck of the tank, this will allow continual flow thru
the tank. This lowers the saturation level of the vapour in the tank & more
fuel will volatize to replace the vapour vented thru the 'streaming vent'.
This also wastes fuel. As well, it will reduce positive or head pressure in
the tank which of course moves fuel from the tank to the engine. Neither of
these things are good.
Hope I have not misjudged the intent of your point Ken. Apologies if so!
Brian #328R
-----Original Message-----
From:
murphy-rebel@dcsol.com [mailto:
murphy-rebel@dcsol.com]On Behalf Of
Bob Patterson
Sent: Sunday, September 02, 2001 8:41 PM
To:
murphy-rebel@dcsol.com
Subject: Re: Sight guages
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You're right, Ken ! That's what I was trying to say - too many
of the vent tubes are inverted "L"'s, forcing air into the line, tank,
and guage. My suggestion was to bend them down into a "J", so there isn't
as much ram effect, or just use a straight tube with rear saw cuts to allow
some air entry. I agree - you don't want a stream of air flowing through
the tank - just enough air getting in so you don't end up with a
vacuum when fuel leaves....
......bobp
-------------------------------orig.----------------------------------------
At 05:12 PM 9/2/01 -0400, you wrote:
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Perhaps this is a statement of the obvious but there must be much more vent
air
flowing than fuel flow for this problem to occur which means that ram air
is
flowing into the J tube and out of the fuel cap vent. Anything that reduces
the
flow has to reduce the error. I put separate guage and vent ports in my
tanks
but I still don't like the idea of flowing air through the tank as it tends
to
increase the likelihood of having a combustible fuel air ratio in the tank.
Ken
Bob Patterson wrote:
Hi Brian !
Part of the problem might be because the vent tube is pointing
forward into the slipstream. Since it is meant to be just a vent, you
could try a straight vertical tube with a couple of saw cuts on the
back side, or bend the front of the tube down into an inverted "J",
so it doesn't get pressurized by ram air.
As Wayne suggests, you might want to check to see that you are
getting enough air INTO the tanks from the caps. I drilled 1/8" holes
at the front AND back of the filler neck, above the bottom of the
cap, so rain wouldn't get in, but lots of air could ! Lack of sufficient
air through the caps is the reason for the cross tube & vent in the
first place .... (At least enough air must enter to replace the volume
of fuel used.)
.......bobp
Wayne, is there a way to redo the vent. Mine is cross vented and if I
blow
into the hole the fuel gets blown out of the sight guages, so when I get
low
it shows no fuel in the tanks. I have already put a restrictor in the
BOTTOM
el of the sight guages and was wondering if there was something else I
could
do to stop the pressure on the guage...Thanks....Brian
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