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Date: Tue, 13 Apr 2010 12:37:54 -0400
Message-ID: <w2j1ab24f411004130937s6088df86p3fd63d33ea88bcd0@mail.gmail.com>
Subject: Mistral Muffler
From: Lynn Hanover <lehanover@gmail.com>
To: flyrotary@lancaironline.net
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 Lynn,
Very interesting, I hadn't seen this design before, I would consider it
simpler to manufacture than the first, therefore  the latest before the
accident. I do like the design because of the simplicity - but there are
things I would change.
Correct me if I'm wrong, but it appears that their mixing (cold air with
exhaust ) within the muffler. I could be wrong here as I can't see down the
cold air tube and there doesn't appear to be any/many air outlets for
cooling within the outer jacket. I would only cool using the outer jacket.
Secondly there is no tube from the inner exhaust housing feeding into the
main exhaust pipe. Of course there doesn't have to be, but to enable maximum
cooling air to evacuate (and mix with the exhaust within the exhaust pipe),
a low pressure area has to be created  - it's what's called exhaust
augmentation in some designs, however in this design it's probably more like
cold air augmentation, whereas the exhaust is sucking in the cold air.
Thirdly the use of cones  at the ends would  help break up the sound waves -
however it introduces complexity and cost.

Overall not a bad design at all, I wonder if the welds at the manifold
broke. In this design there is the opportunity to reinforce those joints
with some flanges. Easy enough to do and the work is hidden.
I wish I'd seen this design before I did mine. there are a couple of ideas I
would consider using.
George ( down under)

In the picture of the interior, there is only an outlet at an angle down and
to the right (in the picture)

In the picture with the cover in place, there is an outlet for the cooling
air at the asme location and anglr, with a flange on it and just a bit
longer than the exhaust pipe. The cover also has an air inlet on the left
end centered.

So it appears to me that cooling air only mixes with exhaust flow in the
down pipe, or even further down if some sort of extension is connected to
the exhaust pipe to carry it further down before it terminates.

If it were me, and I was stuck with this design, I would change the flat
plates at the end of the perf tubes to inverted cones in a thick wall. I
would also add two bungs and plugs so I could use a bore scope to look at
the guts from time to time.

My first attempt to muffle a rotary a rotary racing engine was in a steel
bodied RX-2 at Pocono. It was a Thrush glass packed muffler with an open
center tube. The guts burned out during the first practice.

It set the paint on the floor on fire during the qualifying.

It melted off the rear end during the race. The driver was deaf for a week.
If I were not so anal about thing falling off, that muffler would have
fallen off as well.

My next car was a tube frame RX-7. We dragged it down to Sebring in January.
I had a big Flowmaster. Like Jack Roush uses on his Mustangs. It was real
quiet for a few laps. Then it lost power and came in real slow. The muffler
was blown up like a giant steel pillow. All of the clever baffles were piled
up at the outlet sounding like a giant blender full of steel scrap. Blocking
enough flow to pull us down to about 20 HP.

I pounded it back flat and cut it open. I put full weld beads along each
baffle. I stuck 3/8" steel rods through behind each baffle in two places. I
welded the top back on, and moved the muffler to the end of the system under
the rear bumper. It was under the required 105 Db so we ran Sebring and west
Palm Beach with that rig. I then changed to a 45 pound Borla stainless in 4"
ID, and still run that same muffler.

103 Db or less everywhere.

Lynn E. Hanover

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<div><font face=3D"Arial" size=3D"2">=A0Lynn,</font></div>
<div><font face=3D"Arial" size=3D"2">Very interesting, I hadn&#39;t seen th=
is design before, I would consider it simpler to manufacture than the first=
, therefore=A0 the latest before the accident. I do like the design because=
 of the simplicity - but there are things I would change.</font></div>

<div><font face=3D"Arial" size=3D"2">Correct me if I&#39;m wrong, but it ap=
pears that their mixing (cold air with exhaust</font>=A0) within the muffle=
r. I could be wrong here as I can&#39;t see down the cold air tube and ther=
e doesn&#39;t appear to be any/many air outlets for cooling within the oute=
r jacket. I would only cool using the outer jacket.</div>

<div>Secondly there is no tube from the inner exhaust housing feeding into =
the main exhaust pipe. Of course there doesn&#39;t have to be, but to enabl=
e maximum cooling air to evacuate (and mix with the exhaust within the exha=
ust pipe), a low pressure area has to be created<font face=3D"Arial" size=
=3D"2">=A0 - it&#39;s what&#39;s called exhaust augmentation in some design=
s, however in this design it&#39;s probably more like cold air augmentation=
, whereas the exhaust is sucking in the cold air.</font></div>

<div><font face=3D"Arial" size=3D"2">Thirdly the use of cones=A0 at the end=
s would=A0 help break up the sound waves - however it introduces complexity=
 and cost.</font></div>
<div><font face=3D"Arial" size=3D"2"></font>=A0</div>
<div><font face=3D"Arial" size=3D"2">Overall not a bad design at all, I won=
der if the welds at the manifold broke. In this design there is the opportu=
nity to reinforce those joints with some flanges. Easy enough to do and the=
 work is hidden.</font></div>

<div><font face=3D"Arial" size=3D"2">I wish I&#39;d seen this design before=
 I did mine. there are a couple of=A0ideas I would consider using.</font></=
div>
<div><font face=3D"Arial" size=3D"2">George ( down under)</font></div>
<div>=A0</div>
<div>In the picture of the interior, there is only an outlet at an angle do=
wn and to the right (in the picture)</div>
<div>=A0</div>
<div>In the picture with the cover in place, there is an outlet for the coo=
ling air at the asme location and anglr, with a flange on it and just a bit=
 longer than the exhaust pipe. The cover also has an air inlet on the left =
end centered.=A0</div>

<div>=A0</div>
<div>So it appears to me that cooling air only mixes with exhaust flow in t=
he down pipe, or even further down if some sort of extension is connected t=
o the exhaust pipe to carry it further down before it terminates.=A0</div>

<div>=A0</div>
<div>If it were me, and I was stuck with this design, I would change the fl=
at plates at the end of the perf tubes to inverted cones in a thick wall. I=
 would also add two bungs and plugs so I could use a bore scope to look at =
the guts from time to time.</div>

<div>=A0</div>
<div>My first attempt to muffle a rotary a rotary racing engine was in a st=
eel bodied RX-2 at Pocono. It was a Thrush glass packed muffler with an ope=
n center tube. The guts burned out during the first practice. </div>
<div>=A0</div>
<div>It set the paint on the floor on fire during the qualifying. </div>
<div>=A0</div>
<div>It melted off the rear end during the race. The driver was deaf for a =
week. If I were not so anal about thing falling off, that muffler would hav=
e fallen off as well. </div>
<div>=A0</div>
<div>My next car was a tube frame RX-7. We dragged it down to Sebring in Ja=
nuary. I had a big Flowmaster. Like Jack Roush uses on his Mustangs. It was=
 real quiet for a few laps. Then it lost power and came in real slow. The m=
uffler was blown up like a giant steel pillow. All of the clever baffles we=
re piled up at the outlet sounding like a giant blender full of steel scrap=
. Blocking enough flow to pull us down to about 20 HP. </div>

<div>=A0</div>
<div>I pounded it back flat and cut it open. I put full weld beads along ea=
ch baffle. I stuck 3/8&quot; steel rods through behind each baffle in two p=
laces. I welded the top back on, and moved the muffler to the end of the sy=
stem under the rear bumper. It was under the required 105 Db so we ran Sebr=
ing and west Palm Beach with that rig. I then changed to a 45 pound Borla s=
tainless in 4&quot; ID, and still run that same muffler.</div>

<div>=A0</div>
<div>103 Db or less everywhere. </div>
<div>=A0</div>
<div>Lynn E. Hanover</div>
<div>=A0</div>
<div>=A0</div>

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