Subject: Exhaust manifold length
From: Rotary Engine
Date: 3/8/2006, 9:42 AM
To: AAme


 >
 > One other point Paul, I like your compact manifold for its simplicity,
 > but I think there is VE to be gained by using tuned lengths, have you
 > considered a rolled 32 inch primary manifold?
 >
 > Hans

-------------------------------------------
 > Which manifold. The one in the last 3D is not complete. For max torque
 > and max BSFC at 6000 RPM the optimum runner length is around 25 inches.
 > Max HP is around 7000 RPM with this manifold length.
 >
 > Optimum exhaust pipe length is 32 inches long because the speed of
 > sound
 > is 1700 FPS in the hot exhaust gases rather than 1000 FPS in the cool
 > intake > manifold air.
 > Paul Lamar

-------------------------------------
Right, I meant the TC exhaust manifold, thought you would know that
from the 32 inch reference.

Hans

Yes in theory but no room for it and more work to fabricate.

Paul Lamar ...No rotor no motor.

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

------------------------------------------------------

I had no idea how really efficient the rotary exhaust was until I read
the exhaust valve dumping losses on the R3350 TC SAE paper.
You should take a look at turbo compounding down the
road after you have something to sell in quantity.

Thanks for the pictures Francois. The muffler looks great.

BTW how is the European certification process coming on the
Mistral Wankel rotary aircraft engine?

Will you be at Sun N Fun this year?

Paul Lamar ...No rotor no motor.

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