Listen up Grasshopper,
1. If the engine is carbureted, you may be out of luck
as there is no way to control the F/A ratio in each cylinder. However,
you can try step 3 for informational purposes if you have the equipment
listed in step 2.
2. You must have an engine monitor and sensors that display (or record)
EGT for each Cyl and the fuel flow.
3. Injected engines must perform the GAMI lean test before a
"next step." At 75% power (that means at or above 6500 MSL, 7500 if
using ram air and KIAS is less than 190, or higher), WOT (necessary to
control air distribution when running LOP) .
a. Starting sufficiently ROP, lean in small
steps (less than .3 gph) and record the EGT for each step for Cyl 1.
Continue past peak EGT for that Cyl for about 50F degrees LOP or until ugly
roughness.
b. repeat "a" for each cylinder.
c. Check the gph for each cyl peak EGT.
If the spread in .3 gph or less, you are done and you should be able to run
LOP 20F, 30F, 40F depending on the spread).
4. If the spread is GT .3 gph, you must fix the A/F
ratio. A cheap way to start is to provide equal air pressure to each
injector - a wee plenum distribution to each shrouded injector) and repeat
the Lean Test.
5. if the lean test shows the proper spread, go fly LOP (less
than 75% power)...................
6. If the lean test fails (GT .3 gph spread), consider different sized
injector nozzles (either GAMI or others) for the rich/lean cyls.
Grayhawk can fly a 320 at 8500 MSL, ROP, 9.5 gph and see 195
KTAS or LOP, 7.5 gph and 186 KTAS (all things being equal) thus eliminating
a fuel stop at 3.5 hours cause he could go another hour. 195 x 3.5 = 683,
186 x 4.5 = 837, 837/195 = 4.3 + 1 (re-fuel stop time) = 5.3
Duh!
Grayhawk
In a message dated 8/24/2009 2:40:57 P.M. Central Daylight Time,
Tim@5000feet.com writes:
Hey
guys, I am remembering a long time ago reading about
how the air
pressure surrounding the injector can affect how
well the injector
works. If I'm not mistaken, turbocharged
engines even use some
pressure manifold around the injector
to accommodate for the increased
Manifold Pressure.
What gets me curious is that I'm having a
discussion with some
folks right now who are all having problems
running Lean of Peak
and their engines stumble before they get to peak
EGT. Between
the group, there are a variety of ignitions such as 2
mags
or 1 lightspeed and one mag, and varieties such as 8.5:1,
9:1,
and 10:1 compression ratios, but the one constant is that
they all have
what is purported to be a more effective cowl...
the Sam James cowl
with a plenum. So I'm wondering if the
knowledge base some of you
have would provide any insight
to the issue. I originally was worried
that the 10:1 pistons
might make LOP operation harder to accomplish,
but perhaps
there is just too much air pressure on the outside of
the
injector? The cowl is known to often have too little
exit
area, so it could be that the pressure differential is
even too
high between the top and bottom half of the
cowl.
Any insight
you can give?
Thanks,
Tim
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