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Oh well, I don't
really care why it happened. I figured it was only a matter of time
anyway.
It really doesn't matter in practice what the
equivalent displacement is. Power to weight, bsfc, and TBO are the only really
important numbers. If you choose the magic displacement hypothesis you can
still develop a fuel curve for the engine. The key is a 2 cycle and a 4 cycle
engine are both Otto cycles thermodynamically. Using immaculate ingestion, the 2
cycle should have a volumetric efficiency near 200%. We all know this is not the
case. The Wankel is also an Otto cycle engine thermodynamically. Each rotor is
capable of simultaneously processing 3 separate charges in various states
of induction, compression, expansion, or ignition. Concentrating on the
single chamber in isolation ignores this fact. To calculate VE you
have to look at the "packets" of charge being processed, regardless
of what the E shaft is doing. What it could theoretically do vs what
it does in actuality is the true VE.
Relative displacement is only important
if you are trying to quantify the relative merits of the engine VS other forms
of engine hardware. Obviously the Wankel has many mechanical
merits, it just doesn't change the laws of thermodynamics. Mazda has numerous
reasons to portray this in the most favorable light, both for marketing and
taxation reasons. Apparently some of the true believer rotary extremists don't
want this Mazda 1.3L wink and nod displacement questioned because it removes
some of the specialness from their chosen brand of internal
combustion religion. All of this is thankfully lost on pointy headed
taxation bureaucrats and marketing weenies.
I viewed the "argument" as a discussion and was
merely striving for clarity and correctnes of thought here. It does no good to
perpetuate a false understanding of something.
Monty
Imaculate
ingestion! I like that. I don't know though. I keep
telling him it's a 3.9L
engine and haven't been banished yet. I will
say that I think the discussions
(or arguments) have clarified my
understanding of how the Wankle works. I
haven't though about the 120%
VE at all. If measured properly, it shouldn't
make any difference what
you think the displacement is.
Bob
W.
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