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OUTBOARDER
12-18-2011, 01:52 PM
Figuerd it out finally
Mark75H
12-18-2011, 04:56 PM
Very nice.

I do not understand what the ft/cycle in/cycle relate to. Are they sound? At what temperature?
OUTBOARDER
12-18-2011, 11:50 PM
Very nice.

I do not understand what the ft/cycle in/cycle relate to. Are they sound? At what temperature?

600 mph is used for avg wave velocity bouncing in and out thru stack, carb, venture and reeds @ sea level.

1Cycle is 1 rotation, inches wave travels during 1 Rev of engine is inches/cycle times avg speed. To get 3rd overtone divide by six.
The guys with the six second kawi two-stroke bikes tune for second wave or divide by 4 .

Because reeds stay open or closed for a while there is also a effective range of about 1,200 rpm .
Seagull 170
12-19-2011, 01:57 AM
Where does the exhaust port duration come into this calculation?
Fastjeff57
12-19-2011, 04:49 AM
And it HAS to!

Jeff
OUTBOARDER
12-19-2011, 06:01 AM
And it HAS to!

Jeff

This is for a reed or rotary valve LOOPER , exhaust waves do affect crankkcase pressure but is NEGLIGIBLE for calcing intake side tuned length.

The table results are the same as the TSR program used by many.

Talked with him about theory and he was one of the first to put known formulas to software for racers.
His Yamaha RD400 Twin held quarter record 9.37@143mph for over a decade.
Seagull 170
12-19-2011, 08:04 AM
Sorry my mistake as it looked like you were calculating the exhaust tuner length for a 3 cylinder motor with an equal length 3 into 1 tuner.
I wasn't aware you could apply Helmholtz to reeds, I though it only worked on piston & rotary ported motors, oops, back to reading the books.
OUTBOARDER
12-19-2011, 02:57 PM
Sorry my mistake as it looked like you were calculating the tuner length for a 3 cylinder motor with an equal length 3 into 1 tuner.
I wasn't aware you could apply Helmholtz to reeds, I though it only worked on piston & rotary ported motors, oops, back to reading the books.

We will be testing a couple of 3:1 exhaust chambers on a 49 ci OMC in the near future.
Will use sst60 test wheel to compare.

PWC TRIPS picked up 15 Hp from the pipe.
hupiveneilija
11-29-2019, 01:03 AM
Figuerd it out finally

Old thread, but is that "3rd wawe number" inches from reed tip to intakes outer edge?

Thanks, Jani