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From: <Sky2high@aol.com>
I have always observed high fuel flow readings on my VM EPI 800 system. This
information applies to any user of a FloScan device and any VM fuel system.
My indications were 5 to 10% high as evidenced by the fuel used total as
measured against refilling the tanks at the same airport, using the same truck and
the same position for the airplane.
After discussions with VM, utilizing a second calibrated FloScan, long talks
with David McCluskey at VM, here is what actually solved the problem today:
There are at least 2 ways to hook up the FloScan in the path to the fuel
spider on a 4 cylinder engine. The in/out ports are tapped for 1/4 pipe thread
while the flare tube fittings are for 1/4 inch flare fittings with the usual 1/8
pipe thread. One flare fitting was screwed into a 1/8 female to 1/4 male
bushing and then into the device (right side of picture). The other flare fitting
was a single unit that had the male 1/4 pipe thread with an approximate 1/8
inch hole (left side of picture). The "IN" side of the FloScan is an
approximately 1/8 inch diameter hole that has a chamfered entry to minimize turbulence
(center of picture).
If the single unit is used on the input side, notice that there is an 1/8
inch hole opening into a larger chamber and then into the FloScan hole resulting
in much turbulence. However, if the bushing is used with its large opening
there is no turbulence since it is a large chamber just emptying into the
FloScan.
When I made such a change today (moved the bushing method to the input side),
my fuel flow at idle went from 2.1 gph to 1.2 gph. At cruise at 8500 feet(p
alt), leaning to same EGT, same MAP, same RPM, the old incorrect flow was 10.1
gph, the new was 9.3 gph. The flow at climb went from 15.5 gph to 15 gph.
Note that the error was greater with less flow. I am sure that further flights
will show that the fuel total will now be accurate.
Incredible!
Scott Krueger
Sky2high@aol.com
LNC2 N92EX IO320 Aurora, IL (KARR)
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