NetHeads,
After years of threatening to do it, I finally got around to installing
water injection on my plane, and test flew it today.
I ran water injection on my 2110cc Karmann Ghia back in the late 70's
when I lived in the desert, to tame the detonation caused by the 9.9:1
compression ratio (lots of long stories in that sentence). It was only
activated above certain throttle settings using an adjustable vacuum
switch, squirting water down the throats of twin Weber 40IDF carbs, and
worked quite well. What I didn't realize is that water injection also
"steam cleans" piston tops and combustion chambers, because when I
pulled the heads to lower the compression, the chambers and piston tops
looked like new!
I don't have detonation problems with the latest incarnation of my
2180cc airplane engine, especially since I dropped the compression ratio
to 8.1:1 so I could run 93 octane auto fuel on the hottest summer days,
but I do like the idea of keeping the chambers and pistons squeaky clean
and deposit free. So I found a "windshield washer kit" on ebay for $12
that uses a pliable plastic bag for the reservoir, allowing me to easily
fasten it to my engine mount in an area that is otherwise quite tight on
space.
I can report today that running the injection at near wide open throttle
is barely perceptible, indicated only by a 20-30 rpm drop in RPM, and it
makes the engine run slightly leaner, according to the mixture meter. I
installed the push-button switch that came with the kit, but only used a
pint or so of water in two minutes of operation, so I'll probably
install a toggle switch so I can run it for 10 minutes to empty the bag
and do some serious cleaning.
I welded primer port fittings into the intake manifold for each cylinder
(total of four), with a standard .020" diameter primer nozzle installed
in each cylinder's inlet manifold runner for the primer system. Since
the engine starts without priming in the summer, I simply disconnected
the fuel line and slipped the plastic tubing into the tee that goes to
each side. Works like a charm. I was concerned about the primer
nozzles sucking water out of the bag at high vacuum (idle), so I also
bought a $10 "pneumatic" 12V solenoid (a Keurig coffee maker replacement
part) from ebay so water only flows when I want it to.
Although this likely falls under the heading of "stuff you don't need",
I like the idea of having clean combustion chambers and piston tops, and
a quick way to quell detonation should it ever happen with this low
compression ratio. Obviously, this won't work in freezing temperatures,
but it's not needed for detonation in the winter anyway. See enclosed
photo for my rather shoddy (but temporary) installation, but it does
work fine this way. As you can see, real estate is limited, so a normal
hard plastic reservoir wouldn't fit. All electrical connections are
insulated and there's a fuse and a breaker in the line also.
See http://www.n56ml.com/ghia2.jpg for a picture of the Ghia (still got
it), and see the water injection "installation" photo below this message
as an attachment.
--
Mark Langford
ML at N56ML.com
http://www.n56ml.com
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