I thought this was an interesting concept:

http://cp_www.tripod.com/rotary/pg27.htm

The text:

"


     Peripheral port secondaries

This idea was originally created by Mazda during the mid-late 1960s with
experimental engines. It was also used in Cosmo racing engines. However,
as the Cosmo engine made a mere 2 horsepower more than the standard
production engine the idea was not used thereafter. (This small gain is
probably because of the noise restrictions placed on it, hence not being
able to use a suitable exhaust system).

My friend resurrected the idea and to recently it has been used by
others. Due to the sizeable intake ports - the peripheral ports are 45mm
diameter plus the street ports, the volumetric efficiency is very
impressive. Volumetric efficiency is a measure of the ratio of the
combustion chamber size to how much air can enter the engine while the
intake port is open, and in turn the more air/fuel mixture the higher
the power.
In fact, this engine MAY almost be over 100%. This means that the engine
_takes in more air than it's capacity,_ which is unusual for a naturally
aspirated engine - normally only turbocharged engines and highly tuned
racing engines are capable of this. This explains why a peripheral port
engines are high powered.

In fact, a 13B with this configuration with a Holley carburettor,
electronic ignition, muffled exhaust has been dyno tested at 350 BHP
("flywheel horsepower" -calculated by the dyno)
Furthermore, due to the peripheral port secondary being a "static column
of air", this /tends/ to stop the traditional peripheral port rough
idle. This is because the air is not flowing into the port, so it has a
certain amount of resistance to movement or 'springiness' which limits
how much of the exhaust gets around the apex seal into the fresh mixture.
Also, as the air tends to be very turbulent due to the air streams
colliding, atomisation is good, resulting in a torque curve which is
quite flat across the RPM range.

Given the characteristics across the RPM range, this engine combination
is almost comparable to a turbo engine. It was not much more difficult
to drive than a standard engine. The only problem is that this engine
requires a reasonably free flowing (noisy) exhaust.

*Construction of the engine*

The "Mazda Factory" primary ports in the intermediate housing are filled
with epoxy such as Devcon or similar, as described in the Racing Beat
catalogue.
The street ports are a conventional street port. Sorry, I'm not sure of
the exact port shape or timing used, but I think it was fairly close to
stock to enable good low down torque (which is also boosted slightly by
the relatively long induction tubes.)
The peripheral ports are made by having a machine shop bore a hole into
the housing. Into this is pressed a sleeve which has an interference fit
along with some industrial epoxy.
(The sleeve made out of a certain type of aluminium close to that of the
housing (i.e. same thermal expansion rate), "interference fit" means
that the hole is 45.00mm, while the sleeve is 45.05mm.. this ensures a
very tight fit that won't move!)
The sleeve then needs to be cut off and ground back 1-2mm from the
inside of the rotor housing. This avoids the apex seal being damaged or
worn prematurely.
A bonus of this method is the ability to make it "look stock"..
Essentially this means that the port is flush with the surface where the
side housing ports are.. That is to say that the ports are in the SAME
PLACE as where the water flows from the engine to the manifold. Because
of this, the manifold can bolt directly onto the engine and seal the
port-manifold gap with a stock manifold gasket!
(Usually the connection between the manifold and the port intake is done
with a short length of radiator hose and some clamps.. yuk!!)

*Limits of the engine*

What are the limits of the peripheral port design? Maybe it is possible
to use some big bridge ports where the original (Mazda factory) ports
were. If the improvements in engine breathing can make 350hp with a
street port and a peripheral port, maybe bridge ports would make 450hp??
We also thought that a peripheral port further around the housing could
be used successfully with a turbo.. Just like racing beat's peripheral
port turbo 900 hp 3 rotor 13G engine!!
An even /weirder/ idea would be to put in TWO peripheral ports per
housing! an intake 45mm wide x 90mm long is a /mighty big port!!
/Another option is to run the engine on methanol. Due to methanol's
characteristics of taking heat out of the air as it evaporates, this
cools the air making it denser. Denser air = higher volumetric
efficiency = higher power. (a bridge port on methanol makes 250+ hp)..
Perhaps it would be possible to make 500hp from a /naturally aspirated/
engine!!

The "Scoot" RX7 uses the normal side intake ports plus a peripheral port
and a single turbo to make over 700hp from a 13B."


I guess it does make the intake much more complicated..


Matt-



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