Sean Dennie wrote:

I`m sure you have
 probably
discussed this to great lengths with everybody under the sun and have
your own beliefs, theories and perhaps a convincing method of conveying
those. As merely a rotary enthusiast, I have not really explored the notion
that the true displacement of the rotary could be anything other than what
Mazda and the SAE calculate it to be. I am now in such a debate myself and
am bombarded by opinions and theories (some of which are convincing)
from other rotary enthusiasts. The problem is that the lack of factual
evidence from a reputable source makes this debate, in my opinion, a moot
point.

The debate centers mostly on the notion that the rotary should be rated at
double the displacement that Mazda and the SAE say it is. Personally I always
agreed (and even argued until I was blue in the face) that this was the
correct method but I am nonetheless open to the idea that it might not. The
general opposition is not even unanimous on what the displacement should be.
Some will argue that it should be doubled and others will contend that it
should be tripled. Then you have motorsports
sanctioning bodies who handicap rotaries based on a factor of 1.5 to one!

a seemingly trivial question from an ignorant enthusiast. All the best to you
and thanks again for your time.

Sean Dennie

No debate! 1.3 Liter two cycle two cylinder equivalent.
Anything further than that is like debating religions.

Paul Lamar

That is true Vance. It is a four stroke but just like a two cylinder
two stroke engine it is a two rotor and that fires twice per rev
and displace the same volume just like a 1.3 L two cylinder two stroke
piston engine.

Paul Lamar

Displacement:
The maximum volume minus the minimum volume times the number of chambers or
cylinders.

The actual displacement calculated by the Japanese is (or was years ago) on a
data plate on the firewall. This was required by various countries to
determine sales taxes or VAT and use taxes and insurance charges. If I
remember correctly, it was 573X2= 1146CC for a 12A. This displacement is
recovered in one revolution of the crankshaft just exactly the same as the
calculation for a 2 cylinder 2 cycle engine. There is no confusion at all if
you stop thinking about it right there.

Very few people will stop right there however, and the confusion begins.

The Sports Car Club of America tells me in the rule book that my 12A engine
displaces 2292 CCs. That should be good for around 490 HP instead of the
245HP I am getting. This figure is twice the actual displacement, so it is
obvious that they are not using the Geared six cylinder equivalent that I
have seen in writing. They just turn the crank two complete revolutions, the
same as you would have to do to recover the total swept volume of a four
stroke piston engine.

This is a feeble attempt to compare two engines for the purpose of predicting
potential performance. It does not matter at all what they publish. They try
to keep the various cars at about the same performance potential by adding or
removing choke size or adding or removing weight.

The only analogy that fits, is the 2 cylinder 2 cycle. All of the
displacement reported in one revolution. This is not a feeling, or an
opinion, like liking Santa and apple pie  not liking spinach or the Easter
bunny.

Lynn E. Hanover

 
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