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One thing I forgot to mention about the muffler
design. It is referred to as a "reactive" type muffler as contrasted to an
"absorbtion" type muffler. From my research it appears that "absorption"
type mufflers (packed with fiberglass,steelwool, ceramic wool, etc) appear
to be most effective in filtering out exhaust frequencies around 1000Hz and
above. The reactive (sometimes referred to as sound canceling) muffler is
more effective at the lower frequencies such as 50-400Hz.
Since at 6000 rpm the dominate frequency of the
exhaust is the frequency of the exhaust pulse at 200 Hz (combined ports) or
100Hz (separate ports), I decided that the reactive approach would produce
better results.
Besides, I had tried the
absorption approach earlier using a ceramic wool absorption
material. While it did soften the high frequency metallic sounds of
the exhaust, it really did not decrease the overall volume very much.
Besides that - while the ceramic wool survived the heat of the exhaust - the
force of the exhaust pulses soon pulverize it into dust.
The spintech muffler is in the reactive muffler
category.
FWIW
Ed
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