At the beginning ? there was the reciprocating engine.
2-strokes and 4-strokes.
Nowadays, 2-strokes are hardly used anymore.
Any reputable engine is a four-stroke. This is our standard, our base
engine we compare another engine with.
Then, the Mazda Rotary engine arrived on the scene. What is this? How
does it work? How much power per its displacement? Well, what is its
displacement?
All these questions come up, naturally.
So what do we do? We simply compare it with the known 4-stroke RPE. Not
least, as the Rotary also works on the 4-stroke principle.
A [SINGLE CYLINDER] reciprocating piston four-stroke requires "two"
crankshaft
revolutions to complete its four-cycle operation. Accordingly, its
displacement is
that achieved at two shaft rotations. [I don't think so Rolf. Check
Taylor]
In comparing power and displacement, we must obviously use the same rpm
for all to be equal and one standard for all engines regardless if RPE
or Rotary.
The Mazda RX7/8 displaces 650 cc per rotor and per rotation. At two
rotors and two rotations the displacement is 2.6 litres.
Up to just recently we were all in agreement with that.
Then, Gordon arrived at the scene?.
Gordon makes no mistakes with his calculation; however he does with his
designations.
Gordon uses now two terms: A) the "equivalent displacement" of 2.6 litre
and B) the "real displacement" of 1.3 litre. For the term 'real' he uses
at times 'actual' or 'effective'.
We all know the Rotary is equivalent to a 2.6 litre RPE. By doing so we
are able to use the same formula, the same rpm, the same everything. No
problem.
Saying the Rotary is a 1.3 liter does confuse things. The formula must
be changed; both engines can no longer be compared on the same basis.
All is just 'wrong'.
Why coin a new term for the Rotary such as "real displacement" when it
is not usable with the same existing formula? Doing this we are unable
to compare it with the RPE, which is what we wanted to do at the first
place. We want to know how it 'compares' to the RPE we are all familiar
with. That is what it is all about.
Coining a new term for the Rotary and calling it by only half its
displacement is simply deceit. Mazda used it for tax reasons. As I
understand it, lately they are not using it anymore, but just calling it
the Rotary.
To make the four-stroke Rotary 'equal' and 'comparable' to a four-stroke
RPE, we must call it a 2.6 litre engine. Otherwise we are cheating. We
are trying to say it can make twice as much power per displacement as an
RPE, which it cannot.
Regards
Rolf Pfeiffer
I agree with almost everything except were noted above in brackets.
Paul Lamar
Rolf,
I'm glad you acknowledge that my calculations have always been correct.
It is also true, like you point out, that in order to make
calculations for the rotary engine based on its "published"
displacement of 1300cc for a 13B engine, you need to change the
volumetric flow formula to reflect the fact that each rotor is
firing once per revolution -- instead of once for every two
revolutions for a piston.
However, this is the actual true reality. If we want to use the
piston formula without changing it, we need to double the published
displacment of the rotary.
Fine, I have done that to satisfy the Paul and the rest of you
flat-earthers. Now we can compare pistons and rotaries using the
same formula. (Not that it is a big deal -- there is only one small
change between the two: rpm; the formula for piston engines divides
rpm by 120 because there are two revs for a cylinder firing, while
the rotary divides revs by 60 because there is one firing per rev.
This is reality.)
Okay then, let's ignore reality so we can compare the two engines
using the exact same formula for calculating volumetric flow. We are
now pretending that a 13B engine has a displacment of 2600cc and
each rotor fires once for every two e-ahsft revolutions.
But what happens now if we want to construct a mathematical model of
the rotary engine's vibration characteristics?
Since we are now calling it a 2600cc engine, we necessarily must
assume that each rotor is firing ONCE every TWO revolutions. And
that the total combustion volume is double.
What does this do to the torsional vibrations? They will be
completely wrong -- a two-rotor engine will now have the
instantaneous torque peaks of a one-rotor. And the twisting
deflection on the e-shaft will be twice as big.
Can this be correct?
See what happens if you want to ignore reality and PRETEND?
What will be the solution to model the engine vibrations using 2600cc?
Regards,
Gordon.
Gordon, your language is imprecise and that is a lot of the problem.
What you mean here I think is "each rotor is firing once per revolution"
[of the rotor. Not the e-shaft.] The rotor rotates at one third E-shaft speed.
As such it is impossible for the one chamber in the rotor to intake, compress,
expand and exhaust in one e-shaft revolution.
Lets drop this subject guys. Nobody is going to convince anybody else.
It like religion or politics. As far as modeling is concerned 2600 gives
the right results.
Paul Lamar ...No rotor no motor.
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