I thought about this for a couple of years off and on and I now
think I understand it. Basically what the dynamic chamber does is
double the length of the runners at low RPM and works like
a shorter runner at high RPM when the airflow is much higher.

Note the hump in the HP curve at 3000 RPM. Also Mazda does not say what
this is compared to but I suspect it is the old short four barrel carb
four port and six port manifold set up as on my 74 RX4 and my 76 Cosmo.

This is not really needed in an aircraft as we don't need more
torque at 3000 RPM. Now if you wanted to make it half the length
Mazda made it to enhance the power at 6000 RPM that might be
something to try on the dyno.

The sketch (Fig 4) is not really a simple dynamic chamber.
It is best described as a compound dynamic chamber. Or a two
speed dynamic chamber. It is something Mazda implemented on the
93 and later turbo engines. Second gen engines had a one stage
simple dynamic chamber I think. I don't have a HP curve for this
engine scanned in and the effect would be masked by the turbo anyway.
This is all discussed in Mazda SAE paper 900036.

Note also the low speed and high speed labels
are reversed in error on the sketch (Fig.4).

It is downright amazing that Mazda has continually increased the
power of the NA 13B rotary since 1974 without increasing the displacement.

Paul Lamar

Gordon Robertson wrote:

hi Paul,

Do you have a reference, or could you post the Mazda SAE paper 900036 ?

Gordon Robertson

That is too much to scan and upload. You can get those directly from
the SAE or any good college library will let you copy them.

Paul Lamar
 
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