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
Relook at my 3 cylinder comparison - all pulse locations and
durations are
the same. the total volume processed is the same. The durations
of
the
expansions are now the same (and that is relavent in the
description
and analysis of the cycle). While the Wankel runs 6000 "rpm" to
do this the the piston engine only has to run 4000. that must
mean
that it is better? :) - no! they are just equivalent!.
I really do not know why I continue to argue this point since I
have
nothing to gain either in financial or prestige. just my drive
for
knowledge and truth in engineering. You have a right to
disagree,
and as you state there are references that have bought into
these
claims - so I shall drop it here. Vance
Your illustration lacks the rotary's expansion curves of the
Ansdale
illustrations.
When you add those I think you will see your misunderstanding. Cut
and
paste.
If you try to wiggle out of it I will do it for you so you better
spend a bit
more time on this :) Also fix your web site. I don't want the
world to
be
misled :)
Paul Lamar
In this diagram Vance's three cylinder diagram is shown first. It is
identical to Ansdale's
three cylinder diagram except Vance calls it the fire cycle and not
the
expansion
cycle. Vance shows the piston moving down while Ansdale shows the
chamber volume increasing
to a max. Same thing. So far so good. What is OK for Ansdale is OK
for
Vance and vice versa.
The third diagram is a two cylinder with the same sort of diagram
ideas.
Chamber volumes
are shown increasing and decreasing as a function of the output
shaft
angle.
I can't for the life of me figure out why Vance will accept Ansdale
analysis
of the three cylinder and not the same sort of analysis of the two
cylinder
and the rotary.
I'll say one thing about Vance. He forced me to clarify my thinking
on
this subject.
It is now severe clear.
Paul Lamar
Ops forgot the diagram again.
Paul Lamar
As you say - my diagram reflects piston position rather than max volume
up
as Ansdale used.
All three of his diagrams are correct - as far as they go. and if he had
used the proper cycle
based time line (wankel 270 degrees for the same "stroke" as 180 degrees
for
the pistuns)
as I did, he would have realised that the three cylinder is an exact
match,
where the 2 cylinder
is not. There are three chambers in the Wankel (count them) and each is
carying a charge
of working fluid - a "stroke takes 270 degrees (as if it were geared) -
the
only reason that
you cannot equate that to three cylinders is because it is counter to
your
desires. The 2
cylinder concept is almost more bogus than the one cylinder concept, and
probably only
has credibility since that was a concept they managed to sell to the
German
tax man.
Actually the scale looks close enough that you coul cut and paste his 3
cylinder curve
ove the Wankel curve. OK now can I quit? (the web page stays) Vance
If you quit I will mention your web page on my web page as being bogus :)
It is very simple once you see the light. It takes three wankel chambers
to equal
two piston cylinders to process the same amount of air in the same time.
It takes all three wankel chambers working together to fire once per rev.
It also takes both piston cylinders working together to fire once per rev.
The amount of air/fuel ingested and processed in a given time period is
intrinsic to the definition of HP.
Paul Lamar
Paul,
Please, for the rest of us post Vance's web site address.
Monty
http://members.tripod.com/~vjaqua
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