Fellow Racers,
I've very much enjoyed the spirited exchanges concerning my beloved rotary
engines. Outboard motors? 2 cycles? Turbines?! Geeze, this is a creative
crowd!
Now if anyone has better data I'm open to correction, but here are the
facts as I know them. Engine displacement:
Model/Year Displacement
10A/71-72 982cc
12A/71-85 1146cc
13B/74-78 and 1308cc
84-95
20B (Dave?) 1962cc
Stock HP for a 12A in the US in the early 70's was 101, in Japan 110, the
4 port 13B was down to 115 HP during it's early (smog year) introduction in
the US while later 13B 6 port engines made 135 HP in stock form. Hot rodded
rotary engine HP can get us deep into the weeds, since (like all engines)
there are a variety of ways to increase HP. (I think Dave has the best
current data on rotary HP. I'm struggling to get over 300 with a naturally
aspirated 13B) One very tough restriction on the rotary that may not be
clear, is that we are restricted to the basic engine configurations (10A,
12A, 13B and 20B) since there are no aftermarket internal pieces (other than
seals and such) and the few hybred (4 rotor, etc) engines built, have seldom
survived their initial dyno runs. Most of the hot rod modifications on
rotaries are restricted to changing the configuration of the intake and
exhaust ports ONLY. How'd you like to be restricted to FOUR potential bore &
stroke combinations?
(With only the 12A and 13B engines having reasonable availability)
The 2 cycle arguement is one I'd avoided intentionally, since this stuff
hurts my head. The rotary has 4 distinct strokes just like a piaton engine,
they just occur in a rotary/reciprocating manner. Without pictures it would
take me many more than "a thousand words" to describe how the thing works,
but I'd be happy to fax simple diagrams to the rules commitee. (Fax #,
please.) I think I once wrote the whole thing out and sent it to our
resident rocket scientist (Dr Mayfield) and scared him away from Wankel
engines all together.
Major difference between a 4 cycle piston engine and a rotary engine is
that each rotary engine cycle extends over 270 degrees of eccentric shaft
rotation vs. 180 degrees of crankshaft rotation in the piston engine.
Got a good laugh out of the RX2, 3, 4 & 7 comments. I have seen exactly
one of each of the earlier cars in the past 10 years and all of these are
SCCA SOLO I cars which attend local hillclimb events. All the others in
this part of the country have long since rusted away. But wait! Who could
forget the Mazda Cosmo (RX5), the R100 and the REPU (Rotary Pick-up). None
of these will win any aero (or looks) contests either. So the percieved
"threat" is the RX7. Other than a fairly decent shape there ain't much
threat there either as I see it. (I've already figured out how to stuff a
SBC in my RX7 when the rotaries "fun factor" wears off.)
Any way I shake this out the X3 factor is way out of sync with what the
rest of the racing world uses. When compared to other types of engines the
rotary engine is clearly being unfairly penalized. It's really not all that
different from all the other engines out there, and it's certainly no turbine.
I hope this helps some of the engineers on the list understand the issue
a bit better and doesn't keep anyone else up at night thinking about it.
Chuck "Wish I had a BC" Rothfuss
"USS Wankel" '71 Datsun RX510
Pole Cat Hollow, NC
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