Tracy & all,

I just reviewed your web page info on the custom-made-by-SpinTech muffler.
When I got to Laura's statement about the splitters, it jogged my memory
about something I'd like to ask about.  The thing that triggered this

e-mail

is her report that there was no significant increase of power without the
splitters (increase in flow and power is the assumed reason for the

absence

of the splitters).

If that is nominally so, that the splitters really don't cut power, then

why

don't we install them on the turbo housings?

Why?

First, there is agreement that the absence of the exhaust splitters on the

4

port turbo engines results in more noise and physical violence to the
muffler and our ears.  We have to go to greater technological lengths to
reduce that added noise.

Next, in the flurry of e-mails just before the current custom SpinTech
configuration was conceived, there were discussions of both the splitters
and of the various cones, etc, ways of dealing with the "supersonic shock
waves" or whatever was getting out of the exhaust ports without the
splitters.
    - I asked a question about the physical means by which the splitters

are

installed - the answer came back that they are installed - and removed -

via

roll pins.
    - It was either explicitly stated, or implied, that splitters from a

NA

(non-turbo) rotor housing could be installed in the turbo housing.  I
believe it was even stated that the roll-pin holes were already there

(even

if they weren't, they could be drilled).

How about this proposal:  If it is true that the splitters could be
installed on your engine, and if you did so and took the sound readings
again, then we might see a further reduction of noise from what you are
presently hearing with the custom SpinTech.

What do you think?

David Carter

The splitters are not in the turbo rotor housings because the turbo is able
to recover a lot of the exhaust  impulse energy and put it to good use.
Hitachi developed a special turbine blade profile to increase this recovery
(used on RX7s).

Yes, we could put the splitters in the turbo housings but it is not an easy
job and requires dissassembly of the engine.  Better to do this befor
building it, or better yet, just buy the NA rotorhousings to begin with.

I have tried it both ways already, and reported on it extensively.  Here's
another comparison that you may find useful.  Finn's airplane with NA
housings (with splitters) and VERY simple 'holey pipe' for a muffler is
about the same loudness as my much more complicated and heavy Spintech
muffler installation with the turbo housings (no splitters).  Yes, the
Spintech with the NA housings would be much quieter yet.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

Finn also has less power.
Picture of Tracy's Spin Tech muffler.

Paul Lamar
 
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