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Chuck writes:
<<Horse Power rating = ALLOT!>>
Beautiful installation. Lots of nice work.
Two comments come to mind from the pictures.
The ignition cables should be grommeted where they pass through the
baffle and should be positively retained to prevent disconnection at
the plug. (you probably already considered this).
Are you sure the air filter is big enough? I know the K&Ns have
the best flow rating but your engine needs about 430 CFM at 2700 RPM
(assuming a volumetric efficiency of 1.0). Any pressure drop translates
to a loss of horsepower. Most filters are flow (SCFM) rated at 1" H2O
pressure drop. A 400 SCFM rated filter would therefore cost about 1
horsepower, no big deal. The pressure drop varies as the square of the
flow so a 200 SCFM rated filter will cost you about 4 horsepower. This
is significant if you consider what those high compression pistons
cost per horsepower. Also consider that those flow ratings are for
CLEAN filters. Remember how much suction you shop vac had when it was
new compared to now, even though you cleaned the filter? After spending
so much care and $$s on those last few ponies I would hate to see you
send some to the air filter knackers.
The air filter flow problem is worse in turbocharged planes because the
flow increases with altitude and the pressure drop is a larger
percentage of the available pressure. For the same power setting, the
airflow through the filter will be 2.5 times greater at FL270 than at
sea level. I use 800 SCFM worth of filter in my IV-P.
You may want to measure the inlet temperature and pressure to be sure
you are not getting radiated or conducted heating (from the engine) of
the inlet air. Use the local pressure, ambient temperature and pressure
altitude to calculate the adiabatic temperature rise of the air in the
plenum. Compare this to the actual temperature rise to see if some
shielding is needed.
For what it is worth, some free advice. You have built a high
compression engine with a custom ignition, cam and exhaust. Before I
flew behind it I would want to have it run at full power on a test
stand to be sure all the bits play well together. Detonation would be
my first concern. Get the temps up to red line (oil & cylinder) and
verify that you do not have too much advance, that your mixture is
correct and balanced and there are no leaks. I would hate to see the
first flight terminate badly. You also want to do a flow and pressure
test on the airframe's fuel system. Be sure you can get the GPH's that
big boy needs.
Keep up the good work!
Regards
Brent Regan
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