Tech. Tip:A TRIP
THROUGH YOUR ATV'S MOTOR
FANTASTIC VOYAGE
by Greg
Hall
(from an idea by Claudia Smith)
© 1996
If you remember the 1966 movie
"FANTASTIC VOYAGE" where they
shrunk a mini-submarine with crew and
injected them into a human's blood stream
then you know what this tale is all
about. What if you did the same thing
only this time dropped the sub into an
ATV's fuel tank. What would it be like?
Well
after being shrunk and deposited inside
the fuel tank you would splash around for
quite a while until you were drawn to the
petcock's pickup tube. First you would be
bounced off the fuel filters mesh
screen then sucked down the tube like
dirty bath water in a tub.
It's
a straight shot down until you make a
right angle turn into what looks like,
from the inside, a rubber hose. This part
is just like a water slide. Soon the
black walls (rubber fuel line?) give way
to a golden color (fuel line nipple?)
then silver (carburetor body?) After
getting bounced off a cone shaped object
as we pass by (float valve?) we fall
straight down into a small lake of gas
(float bowl?)
From
above we here a sound like a wind storm.
Before we can decide just what the sound
is, the intensity increases dramatically
to a deep moan. At the same time we are
sucked below the surface and appear to be
heading toward an upside down tower (main
jet tower?).
With
increasing speed we are drawn to the
bottom of this tower and sucked inside
through a gold colored hole (main jet?).
We are now traveling straight up and the
ride is getting turbulent. There are air
bubbles all around us. They appear to be
coming from holes in the golden colored
walls (needle jet?). We narrowly miss
being impaled on a golden arrow like
structure (jet needle?) centered in a
round hole above us.
As
we pass through the hole we are suddenly
pounded by gale force winds hitting us at
a 90 deg. angle (carburetor venturi?). We
pick up tremendous speed as the wind
carries us along a large passageway
(intake tract?)
Ahead we spot a familiar object, the
intake valve. Luckily it's in the open
position. The wind's force carries us
past it quickly and deposits us into a
dark void (cylinder?) The air currents
have subsided some but we are still being
bounced off the walls (mixture
turbulence?). What a ride!
Suddenly
we are forced upward by an unseen force
(the rising piston?). We start to head
back toward the open intake valve. But
before we can get close it retracts into
the roof of this chamber with a bang. Now
the currents carry us past a protrusion
in the otherwise smooth roof (sparkplug?)
If it is the sparkplug, then this is not
the place to be with the piston fast
approaching!

As
expected, a lightening bolt of
electricity jumps between the sparkplug's
two electrodes. Immediately after the
initial flash there is a secondary flash.
Only this time it doesn't die out. It
keeps growing in intensity. There is a
wall of flame radiating outward from the
center in all directions like a ripple in
a pond (flame front?). The first pressure
waves hit us and drive us toward the
cylinder wall. Directly behind the
pressure wave is the wall of flame. It's
beginning to get quite hot. At least
there doesn't seem to be any glowing
fuel/air mixture floating around us that
is in danger of spontaneously exploding
(detonation) before the normal burning
takes place.

If
there was detonation we would see random
blue/white flashes and be bombarded by
intense heat and shock waves. When these
waves hit the cylinder's wall a harmonic
resonance, better known as PINGING, is
created!
Our
craft is filled with intense yellow light
as the burn continues. Where's my sun
screen? We follow the piston as it
travels down the cylinder just like a
high speed elevator (assuming you ride in
a 1000ft/min elevator). All to quickly
the ride is over as we are now being
chased by that same piston as it starts
it's trip up the cylinder.
Luckily
there is an escape for us, the open
exhaust valve. It is slowly dropping from
the ceiling and we slip past it and head
down a long dark tunnel (exhaust pipe?)
lit only by glowing asteroid-like bits
(still burning gas molecules?).
We
are racing down this tunnel and it looks
like our "Fantastic Voyage"
will soon be over. However this smooth
ride soon ends as it feels like we are
stopped suddenly and sent back in the
direction we just came from (reflected
pressure wave?).

Ahead
we can see the still open exhaust valve.
Around the valve's stem we see fresh
unburned fuel/air molecules, straight
from the carburetor via the open intake
valve (valve overlap?), entering the
exhaust pipe. The wave carrying us
collides with this fuel/air mix. Our
reflected wave gases are at a higher
velocity and larger volume than the
fresh, unburnt mixture. Therefor we force
it back into the cylinder as the exhaust
valve rises to seal the exit to the
cylinder.
With
this direction sealed we bounce off the
closed exhaust valve and start back down
the exhaust pipe again . Again we settle
down for a smooth ride. And again the
smooth ride is disrupted. This time by
what looks like a maze. We are bounced
around as we poke here and there through
the maze of holes, chambers and tubes in
this area (muffler baffles?). Eventually
we do find our way out into the open air.
Quite a trip! Lets do it again! How about
6000 times a minute! Or better yet, how
about seeing what it's like to be motor
oil?
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