Hi Al,
Yep, I agree!! I think we
actually nailed this one down on ACRE years ago (before I got
ex-communicated). But "Da Boyz" do tend to get carried away with the
maths. However, the maths must be applied correctly, with
strict attention to analysing the problem first. This Displacement
controvesy is just another example of not making sure that the fundamental
premises and pre-suppositions are correct before embarking on that murky
enterprise of "Number Running" (Shades of the EWP
fracas!!).
Many years ago, my dear old mentor told me
"Leon, an internal combustion engine is nothing except an air pump,
... gone mad". That really changed my mindset. So if you know
how much air it pumps per cycle, you can compare it to any other air
pump. This is where volumetric efficiency, and the type of cycle (2
stroke, 4 stroke, Wankel etc) comes into the
picture.
Additionally, displacement and air flow are
not necessarily the same thing - RPM comes into it, as well as Vol Eff.
However, in the final analysis, all that
really matters for aircraft use is how much power can be extracted and at
what RPM, and how efficiently the fuel is burned (BSFC- which is another
boondoggle altogether - not going there today!!).
So as for this issue of comparing a 13B to a Lyc
360, using current technology done right, either an REW (with
9.7:1 high comp rotors) or a Renesis 13B (with 10:1 rotors) will make over
200 BHP, as long the engine is allowed to rev to where it makes MAX
RPM, Which is just a function of PSRU ratio, prop size
etc (7,000 RPM min - whereas the Lyc will do a pretty fair impersonation of
a grenade if it goes over 3,000 RPM for long). .
Obviously the manifolding (inlet and
exhaust), and port timing (mild port, bridgeport, PP etc)
must also be conducive to the airflow required to make that power. None of
this is a real mystery as there is nearly 40 years of world wide racing
experience to define sizes and lengths, RPM and power outputs. There
is NO need to re-invent the wheel.
Cheers,
Leon
----- Original Message -----
Sent: Saturday, February 12, 2005 2:58
AM
Subject: [FlyRotary] Re: Last Word on
Displacement was Re: [FlyRotary] Solved!!!! => Rotary AirFlow Equation?
Help?
Thank you; Leon.
That’s how I had always looked
at it; but with all the math spinning about, I thought maybe I had overlooked
something.
Al