Edward Klepeis wrote:

Dear Paul
     I have a question is there any reason  to have 4 tube  on the intake when 
two tubes could do the same job.It makes a
simpler  set up and easyer to weld. please give some feed back you 
 have worked on these eng way long than me i am starting out
and have a lot to learn. thanks for your help.

Regards

Ed

techwelding@comcast.net

Here is the long answer :)

Any time there is a discontinuity in the intake plumbing there is a disturbance
in the wave effect. Each section then becomes its own organ pipe.
Every rotary Mazda has made since about 1982 or so has had individual
pipes for each port. The actual affect of a short Y in one pipe feeding 
two ports on the same rotor is unknown at this time. In theory short 
legs would resonate at very high RPM's out of the range of the rotary. 

Long legs of the Y's 
are used in the 1982 and up RX7's and RX8's intake system. Particularly 
the RX8 intake system as shown here. A Y with the proper length of the legs
connecting two rotors 180 degrees out of phase has two resonate frequencies.
A primary and a a secondary resonate frequency. One at the length of the 
individual leg, the primary effect and one at half the RPM of the individual 
leg, the secondary effect. The wave  travels from one port through the Y 
over to the other port so the length of the path is twice as long.  

Here are some renderings of what such a strictly  secondary effect manifold might 
look like. In this case the short primary resonant mode of the leg between 
throttle and port is not used. Only the secondary effect between 
ports of individual rotors is used.

This secondary effect is somewhat enhanced at lower RPM's by valve overlap but this 
last minor effect goes away with the side exhaust port in the RX8 as all 
valve overlap has been eliminated. The finite physical distance between 
the rotors precludes using this  secondary effect at high RPM. In other 
words it is very difficult indeed to connect two rotors together in such away to
take advantage of the secondary effect at six thousand RPM and above.

Never the less the RX8 generates more HP at any given RPM than any stock side 
ported rotary built to date. Due mainly to a 30% increase in port area. 
The purpose in the RX8 intake system is to broaden the torque curve at low
RPM  for automotive use. It does this by extensive use of the secondary 
effect at lower RPMs. Not needed in an aircraft engine as prop load is at 
least proportional to the cube of RPM. Over about 6000 RPM the RX8 uses 
only the primary effect.

In that case the most HP will be generated at a specific RPM with all
pipes of the same length using only the primary effect. The out 
and out record amount of HP per rotor generated by any rotary at any RPM 
from 6000 up is held by a peripheral port engine with all pipes the same 
length using the only primary effect. Namely the Lemans four rotor.
 
In an electronic analogy this is called a high Q parallel resonant system.

I hope to be able to test some of these ideas (built by others) on my new 
dyno now nearing completion.

Paul Lamar
 
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