Mistral has experimented with various exhaust manifold length and
geometries.  It makes virtually no difference (1% in max power and BSFC
between the best and the worst).  That's experimental fact.

The theory is that the emptying of a rotary's combustion chamber is so
efficient that "sucking gas out" by having a tuned exhaust manifold is
useless. But that is only theory.

So, don't worry about tuning your exhaust system, worry about fitting it

in

the cowling, about containing the heat and about making your system heat
resistant!

BTW, Mistral has developped a double-jacketed primary exhaust manifold,

with

forced air circulation between the 2 walls.  I attach a few pictures.
Internal parts are inconel, external ones, as well as the flange, are
stainless 316.  This component is presently undergoing testing.  It will

be

made commercially available.

Francois Badoux

Francois,
Good work! It looks a nice compact and well made unit.
I have been working with Bill Jepson and between the two of us we have come
up with a double skinned exhaust, with forced air through the centre core
and outer skin. I currently awaiting my fabricator to finish the job - he's
very slow, but cheap!
Do you envisage the cooler air will reduce the noise.
George

Thanks for the compliment George.

The double skin and the flow of cool air in the middle is probably dampening
the noise a bit, but we can't isolate this effect.  Probably more effective
for noise reduction is the turbulence induced by the multiple holes in the
entry sleeves.  This turbulence also helps containing most of the post
combustion inside the manifold. For good overall noise reduction, we
strongly believe that a good silencer is a must.  We are developing an
in-cowl silencer tuned to the frequencies of the 13B (around 200Hz).

Francois Badoux


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