****Begin*****
As always forget to include all the info.  My engine is NA and built up by Bruce with induction porting or what ever he does.

The program I used can be found under "software" at   www.mh-aerotools.de/airfoils/
Its easy to use and do what ifs.  Would have liked more attenuation at 500 hz but limited by volume again.

I increased the diameter of the inside tube and the exhaust tube to 2.5", but kept the same length dimensions.  I got back the rpm loss from back pressure. The dominate noise in cruise is still the wind and not the engine even though more horsepower is being produced.



Todays results:



                      RPM                  DB a               DB c

Idle                    2K                   87                    102

runup                 3K                   90                     106

climb                 5.6K                100                    110

cruise                 6K                   99                     108

cruise                 5.7K                99                     107

cruise                 5.7K                99                     107.5

taxi                     2K                   86                     100

stop                   1.7K                 81                      99



Again did not note any major discoloration of the can or tubes.  Looks like it will last for a time.  May decrease the pitch on the Warp Drive prop a 1/2 degree or so.  It helps to have cooler temps for performance.



TNX

Larry



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