> > > > > >> I talked with Ron at Spintech about a group buy of 2 into 1

 > cruiser
 > > > mufflers fabricated from
 > > >  > >> 321 stainless.
 > >
 > > If you are thinking of not collecting the headers before the muffler
 > you will
 > > be leaving a bunch of power on the table.
 > >
 > > Lynn E. Hanover

 > I agree. As one pulse travels through the collector it's inertia
 > cause a low pressure pulse in the other pipe which of course
 > increases the exhaust flow out of the other rotor 180 degrees
 > out of phase.
 >
 >
 > Paul Lamar

 If the 13B, which is 180 degrees out of phase needs a 31" header for maximum
 power at 6500 rpm, then what header length would a 3-rotor, which is 120
 degrees out of phase need in order to maximize power at the same rpm?  Seems
 to me that something less than 31", like maybe 20-24" would provide more
 scavaging.  Or, am I missing the bigger picture here?

First a collector system won't work on a three rotor.
Tuned pipes will help of course.

The exhaust pulse travels down the pipe at the speed of sound.
As the RPM changes the distance between the pulse changes.
Higher RPM shorter distance. Optimum length occurs as one
pulse is leaving the collector and another is being emitted by
the engine.

The speed of sound is about 880 feet per second.
Each rotor fires once per rev. At 6000 RPM or 100 RPS
pulses are every 1/100 of a second apart or .01 second.
It takes the pulse about .003 seconds to travel 32 inches.
That is an exact multiple of .01 second. So the pressure
wave is bouncing back and fourth in the pipe three times
and the low pressure part of the wave arrives back at
the exhaust port just as the port opens again. This
also sync's in the collector enhancing the low pressure
part of the wave in the other pipe. Multiples of 32 inches
also work such as 16 inches at 6000 RPM.

Paul Lamar

Paul,  let me make sure I understand.  A 16 inch exhaust header is
properly tuned for 6000 rpm.  If this is true, why have we been
struggling to achieve 32 inch headers?   A sixteen inch header is
easy to fit inside most cowls whereas the 32 inch version is damn
near impossible.  If you confirm the 16 inch header length, I will
change mine accordingly.    Jerry

I think I made a mistake looking at the curves. I think I was looking at
the 61 inch curve and not the 16 inch curve. That makes
more sense as the pulse will then bounce back and fourth six times.

Here is a better, higher rez, scan of the curves.

Paul Lamar

Maybe what you can do Jerry is make up a 11 inch and a 23 inch system
and we can try them on the dyno. Those would be one bounce and two
bounce systems if my calculations are correct. A 22 inch system would be
a natural for a tang muff under the cowl if it works. I think Everett
choose the 32 inch system as it got the exhaust out of the cowl
and Mazda proved that it worked over a wide range.

Paul Lamar

BTW my speed of sound was based on a rough guess of 600 MPH.
The speed of sound varies with temperature so corrections must
be made for the actual speed of sound in the pipes. 
I could be off by a lot. I'll have to look it up for 1500 degrees
or so.

Paul Lamar
 
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