This is the definitive comparison of a Mazda Wankel one rotor with
a four cycle two cylinder piston engine. This should put to rest
once and for all any question that the Mazda rotary is anything other
than an 80 cubic inch engine. Either a two cylinder two cycle 80 cubic
inch engine or a 160 cubic inch four cylinder four cycle engine.
I have taken Ansdale's diagram and removed the extraneous info
and enhanced it a bit. Vance made me do it.
Paul Lamar
VJ - OK this is better - It does properly show the displacement of a Wankel
during a completion of one full 4 stroke cycle, and it properly shows
3 chambers each working on it's individual charge of reactants (strangly
that is also a very good description of an even firing 3 cylinder 4 stroke
engine' The two cylinder analagy fall rethe flat since the apparent power
stroke widths , and the gap between them do not corelate with the Wankel,
where my 3 cylinder corelation shows total agreement in all of those areas.
The problem is that fixing on the eccentric rotation introduces enough
distraction
to allow the manufacturer (motivated by money) to rotate the pea under the 3
walnut shells to the distraction of the tax man. Using an output shaft as a
direct reference to displacement is not always a valid approach - just look
at some
other implementations of the Otto cycle such as the Dyna cam and other cam
systems, or even the case of a free piston engine for which the output shaft
(if any ) might be a turbine. The proper time reference is the time for
a charge (be it in a piston, rotor face, or any othe possible combination)
to complete the four strokes of the cycle (in no real way, is a Wankel a
2 stroke engine). There is no configuration to my knowledge where this
approach
would not be valid, and using this the conclusio has to be that the
mechanical
displacement of a Wankel rotor is the sum of those 3 swept volumes. Using
this approach dispells a whole lot of the magic attributed to a Wankel
engine, and all the power numbers, air consumption, BMEP .etc fall into
rational places.
This in no way diminishes the brilliance of Herr Wankel and his associates,
and in no way makes this engine unsuited for aircraft, marine, or automotive
use. It provides dependible power in a compact package, with a comendible
shortage of catastrophic failures. Is this not enough? for you rotory
enthusiasts?
Or is the lack of magic and mystery to much to accept? Magic is very useful
for
entertainment and amazement, but I think I like my airplane engines to
operate on physics and thermodynamics
Vance Jaqua
I think I have finally found the root of your misunderstanding.
Take a closer look at this chart Vance. It is indeed the displacement change
per unit time for the two equivalent engines.
The area differences under the curves are irrelevant. One, the rotary
and the other, a 2 cylinder four cycle engine.
Just because the duration of the chamber volume change is longer
in the rotary is irrelevant.
That IN FACT is why it NEEDS three chambers
instead of only two to equal the 2 cylinder four cycle piston engine
pumping capacity or displacement per unit time!!!!!
The same amount of air and fuel is processed in the same time!
That is the bottom line and that is intrinsic to the definition
of displacement. How can there be any doubt about it?
Paul Lamar
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