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<< Lancair Builders' Mail List >>
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Thank you for your insights on flowtesting. We have a 600 CFM flowbench, have
done quite a bit of flow development on Lyc cylinders, and are always
interested in new developments in testing procedure.
What we asked about was the FLOATing to which you referred in the following
quote:
<<..For ex - 360 Lycoming engine that should produce 180HP you put all 4
cylinders on a bench and float them you'll will get about 160-165...>>
We don't understand the process of FLOATING.
Incidentally, our flowbench doesn't measure power output; it measures the
volume-flow capacity of a given item at a specific delta-P across the item.
How does yours measure power?????
Just wanted to clarify one more misunderstanding. Your claim that:
<<..Upon CFM info retrieval you are then able to determine HP..>>
This is one of the biggest hoaxes out there. The CFM the heads will flow has
NO direct or linear relationship to the HP an engine will produce. There are
MANY, MANY other factors which determine the power an engine produces, and
airflow capacity only determines a MAXIMUM theoretical value the engine could
produce if all the other (interrelated) stuff is right, including, but not
limited to cam lift, velocity, acceleration profiles and lobe positioning,
intake system acoustic tuning, airflow velocity profiles, airflow separation
on the port floor, mixture homogeneity, fuel vaporization issues and SMD
particle size, effective cylinder pressure, chamber swirl and tumble,
flame-front propagation, and other combustion-quality issues, exhaust system
restriction and acoustic tuning, and others.
The only way we know of to determine engine power is to measure it on an
honest, calibrated dynamometer using controlled testing methodology. There
are lots of dynos out there which measure fictional horsepower. In fact, if
you'd like to buy an IO-360 which produces 950 HP, just give me two minutes
behind the dyno control panel and I can show you those, or any other, numbers
you'd like to see.
Some of the goofy power claims out there are the product of just such dynos,
or worse, the product of overly active imaginations. One of the most
ludicrous is the claim that installing 10:1 pistons (LW-11487-S from the
HIO-360-D1A) in an angle-valve Lycoming will yield a 20% HP increase over the
8.7:1 pistons. Oh yeah, for sure!
BTW, on certain engine programs, we have achieved flow increases in
angle-valve Lyc heads as much as 19%, and, in certain cases, sometimes had
that actually DECREASE power.
Jack Kane
EPI, Inc.
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Please send your photos and drawings to marvkaye@olsusa.com.
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