If you get into breathing efficiency then you have to start
with hemi vs wedge 2 valve 4 valve 5 valve SOHC DOHC it get
endless. Sort of pick your own poison on the breathing
thing. The wankle has no advantage at all in breathing a
disadvantage if anything.
Dave Dahlgren
Chuck Rothfuss wrote:
>
> Bill, List,
>
> Great question. There is certainly a "breathing efficiency" issue when
> comparing Wankel engines to their piston kin. Although both share the same
> four Otto Cycle events, (Cycle being a better term than "stroke" when
> referring to a Wankel, since the action of the rotors is in only one
> direction.) each cycle of the Wankel engine extends over 270 degrees of
> eccentric shaft rotation vs 180 degrees crank rotation in a 4 cycle piston
> engine. Comparing power strokes between two and four cycle piston engines
> and Wankel engines then clearly shows the breathing disadvantage that the
> Wankel is graced with. Within the commonly available engines we are also
> restricted to factory displacements and compression ratios which cannot
> reasonably be altered. We can alter port timing and size to increase
> breathing capability, but as Dave's pointed out, 360 HP is about all that's
> possible from a naturally aspirated 13B (1308cc). Best I've seen from a
> carbureted 13B was 328 HP. With my slightly too small carburetor I'm hoping
> to get just over 300 HP next year.
>
> I think it may also be appropriate for us all to start referring to the
> engines as Wankel engines instead of Mazda rotary engines. As Dave
> demonstrated with his engine list, there are far more manufacturers than
> Mazda. The term "rotary" also seems to somehow mislead people into
> believing that the rotor is simply spinning inside the rotor housing. Its'
> movements are far more complex than that. (...and I've actually gotten an
> engineer to adopt my highly technical term... "monkey motion.") There's a
> simple Java demonstration (animated model) of the engine on the same website
> with the Wankel engine list if anyone wants to see how the rotor is actually
> moved around the stationary gear by the eccentric shaft. On this item a
> picture is truely worth a thousand words. Just look around in the "How it
> works" section of the index at <www.monito.com>. Lots of educational
> material there.
>
> Chuck Rothfuss
> Might snow tomorrow in
> Pole Cat Hollow, NC
>
> At 09:26 AM 12/27/2000 -0500, Ardun Bill wrote:
>
> >Chuck, is there an issue of "breathing efficiency" at play here? I know
> >that today's best four strokes and today's best two strokes are not a
> >fair match based on displacement, because the two stroke, although it
> >does not have as good breathing (volumetric efficiency), has a net power
> >output better than the four stroke merely by virtue of double the power
> >strokes.
> >
> >How does the rotary fit into this group, in other words, does it breathe
> >better or worse than its two and four stroke piston cousins? Porting,
> >time available for induction and exhaust, etc.
> >
> >Regards from Ardun Bill where there's a dusting of snow this morning in
> >the Great Dismal Swamp, Chesapeake, VA
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