AD = Adam Wade. PL = Paul Lamar

The physical displacement value that makes the most
sense is 3.9 liters. That is what Vance claimed and
he was right.  All three chambers in both rotors. PL

And since those chambers cycle at 1/3 the e-shaft
speed, you should be figuring rpm based on rotor
speed, since you're figuring displacement based on
total rotor displaced volume.  And guess what happens
when you divide 3.9 L by 3?  AW

It obviously does not perform like a 3.9L four cycle
engine PL

It would at (e-shaft speed) three times the crank
speed of a 4-stroke recip, assuming it was ported to
do so. AW

nor does it perform like a 1.3L four cycle engine. PL

Nope, because a full cycle of all the pistons on a
four-stroke recip take two crank revolutions.  A 2.6 L
recip sucks in 1.3 L of air given a VE of 1.  A "3.9"
L rotary sucks in 3.9 L of air through full cycles on
all rotor faces -- or 1/3 of 3.9 L per e-shaft
revolution, which is...  *drum roll*  1.3 L.  So given
an e-shaft rotational speed, a 13B sucks in as much
air as a 2.6 L recip does with a crank speed that
matches the e-shaft speed.  I'm not sure where you're
getting the idea that a 13B takes in more than 1.3 L
of air per e-shaft revolution, but it's not hard to
prove to yourself that this is not the case by playing
with a rotor, stationary gear and rotor housing on
your kitchen table. AW

So something is obviously wrong with the 1.3L
displacement designation. PL

Nothing wrong at all as long as you're aware what it
represents (the amount of swept volume covered in one
e-shaft revolution). AW

It performs like a 2.6L four cycle piston engine and
a 1.3L two cycle piston engine.

Which would not be the case unless it was taking in
the same amount of air per crank rotation as those
engines (again, assuming VE=1 for the sake of
simplicity). AW

In that sense a 1.3L two cycle piston engine is
really 2.6L actual displacement as it has two
chambers per piston. PL

The problem there is that reed-valve two-stroke
engines have symmetrical port timing, which hurts
their power output and efficiency when compared to a
four-stroke.  That's why we aren't all driving around
in two-stroke cars, and it's why when all else is
basically equal a 500 cc two-stroke twin doesn't
produce twice the power of a 500 cc four-stroke twin
designed to run at similar revs.  Two stroke engines
can usually rev higher because of the light weight of
their reciprocating parts, but the combustion is much
less efficient in terms of power, BSFC, and of course
pollution.  Ever listen to a typical reed-valve
two-stroke idle?  Many of them can barely keep
themselves running due to a lack of sufficient
pressure differential between the intake charge and
the exhaust gases during overlap.

Adam Wade

----------------------------
Nits all :)
Paul Lamar ...No rotor no motor.

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