Notice the length of the pipe on the piston engine was

50 inches

long for 2500 RPM and the optimum length on the Le Mans engine for 6000

RPM

was 16 inches long.

We are nowhere near a workable theory for rotary engines. I am just

pointing out

some similarities with piston engines. Don't try to read something into

this that

is not there.  All of this is empirical. Determined by extensive
experiment on one piston engine of a given bore and stroke. The work

done

by Taylor

is sure to scale only to piston engines. You keep sounding like you are

going to come

with a magical number for the pipe diameter and length. We have a long

way

to go

to come up with a workable theory for rotary engines. Forget it. The

only

way you are

going to do that is by extensive experimentation on a dyno. Build the

dyno.

Why bother anyway? The solution is staring you in the face. Mazda has

done

it for

you. Nobody anywhere has a built a rotary engine with something other
than 2 inch p-port pipes that comes close to the 240 HP at 6000 RPM

achieved by the

the Le Mans engine. Copy the Le Mans engine exactly. What is it about

this

that is

so hard to understand.


BTW Why mess with a ancient 12A engine? It is no lighter than a 13B.

Paul Lamar

One of the major differences involved with intake tuning for a Wankel is

the

shape
and duration of the "suction" pulse as related to the frequency of those
pulses.

The Wankel case is analogous to hooking all the intakes to a single pipe
for a 3 cylinder piston four stroke.  This probably has the effect of
reducing
the "sharpness" of the resonant peak. Obviously tuning works, as evidenced
by the Le Mans engine. Resonant devices are characterized by a "Q" factor
of resonant efficiency - the opposite of damping. Both "organ pipe" modes
and cavity modes (Helmholtz cavities) can be used to support resonance
(or disonance - untuned wave damping") .

If you look at the ranks in a pipe
organ you can see that length/diameter ratios are a factor in the "Q". A

short

length to diameter ratio has poor "Q" since it begins to support other

modes

such as radial and circumferential to the detriment of the longitudinal

that

you are trying to use - ie larger diameter is not always better.
That is my nickel on tuned pipes - for whatever it is worth (we get

exposed

to a bit of this sort of thing when trying to suppress destructive

acoustic

instabilities in rocket combustion) - Vance

Vance,
 It's been a very long time since I've seen anyone use 'Helmholtz' in a
sentence!

One additional piece that I remember from a physics class a long time
ago...might apply?  In the 'organ pipe' mode, if the diameter of the pipe is
smaller than the wavelength of interest, the end of the pipe where the wave
enters acts as a 'point source' for the wave - as if the wave originates at
the end of the pipe and not somewhere else in space.  If the diameter of the
pipe is larger than the wavelength, then the pipe acts more like a 'wave
guide' and just 'channels' a wave that originates somewhere else in the
system.

I don't know enough about the wavelength of the pulses in the intake system,
but could it be possible that the folks using smaller pipes are getting more
benefit from the tuning effects than someone that selects intake plumbing
too large?  I don't know that I've seen the frequencies discussed here.

Andy Hecker

 
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