hopper

[Karl G. Mueller]

Dave,

Friction is certainly one of the factors in pressure loss as is a small
diameter fuel tubing. The greater the distance from carburetor to tank
the more loss of negative pressure (suction) that is created in the fuel
line at the carburetor. This was the main problem with all the fuel
passages on the ST G2300. Just one look at the fuel nipple on the
carburetor, which is the same size as on a .40 size engine, would tell
you that is was too small in diameter. The internal passages in the
carburetor were too small as well. Once I opened these up the carburetor
worked fine.
A larger size fuel tubing would certainly improve the loss of pressure
due to friction. The longer the tubing, the more loss. That would mean
changing all the fittings on the fuel tanks and fuel nipples on the engine
as well. The addition of a hopper tank seems to be the easier way to
circumvent the problem.

Karl G. Mueller
kgamueller at rogers.com

----- Original Message ----- 
From: "David Gundling" <DGundling at compuserve.com>
To: <discussion at nsrca.org>
Sent: Friday, August 13, 2004 8:19 PM
Subject: Re: hopper


Message text written by INTERNET:discussion at nsrca.org
>I am with you on this one. Running a Y.S. 140 without a hopper tank
and than changing to a hopper tank setup I have found that I could lean
the engine by 3 clicks on the needle. Going back to just a main tank
without the hopper the engine was set to lean. This should prove that
it is of benefit to run a hopper tank for any set up with the main tank
near the C.G., crankcase pressure or pipe pressure, 2 stroke or 4 stroke.
<

Karl,

Never played with a hopper tank, however, I suspect that the discussion has
apparently missed the friction factor. There is friction in moving fuel
through a small tube. The hopper tank reduces that friction in the vertical
or any nose up attitude. Wonder if the same effect could be achieved by
making a fitting to allow larger ID fuel tubing to be used? I have measured
muffler pressures with a manometer  as high as 1 psi. That should be able
to lift fuel more than a foot or two even acounting for G loads during
maneuvers. Could it be that suction is not capable of overcoming both
gravity and the friction force at the present high fuel flow rates?

Dave
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