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wrjjrs@aol.com wrote:
Enerest, Please note I mis-typed the line and I believe the noise will increase again as the tuning improves. There are many factors here, timing, mixture and exhaust tuning. If all the other factors remain the same I have found that ported engines are usually quieter when too rich. This is anecdotal, I haven't recorded it with a DB meter. My personal explaination is that the cylinder pressures are higher when better tuned and the sudden port opening in a rotary or 2-cycle causes a louder "bark" The rotary is particularly bad in this respect.
Bill Jepson
Agreed. But consider that you're at the peak of the tune curve, but that curve is very well defined because the fuel varies slightly with each injection. Think of it as drawing the curve with a crayon vs an engineering pencil. You can't really tune it perfectly. It's like driving a car with loose steering or flat tires. On one injection, you have the perfect amount of fuel, the next just a little lean, and the next just a little rich. The rotor next to it is doing who-knows-what. How would you get the max HP out of that? You couldn't, any more than you could win with flat tires in an Indy race. How would that mistune express itself? Well, you would have BIG BARK/little bark/BIG BARK/little bark (repeat at 3 to 6K/sec, ad infinitum). This would set up a resonance signal in addition to, over and above the primary exhaust signature. It would take some sophisticated sound sprectrum analysis to prove/refute this hypothesis, but it does explain a decrease in noise combined with an increase in HP.
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,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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