Placing the throttle close to the rotor housings on the p-port
engine reduces this effect as less exhaust gas is stored.
This is nothing new. The p-port NSU Wankel Spyder had this
feature in 1965 or there abouts.

The draw back to any butterfly in the intake runner
is; it cuts down on the amount of air getting in the
engine and therefore the amount of power generated.
It also causes a slight increase in pumping losses
which increases the fuel burn slightly for a given
power level.

That is why slide throttles are used on high power
rotary engine as well as a lot of piston engines.
Mazda wanted to get the best BSFC possible for
the Lemans engine because the rules specified
a maximum of fuel that could be burned during
the race. That is one reason the Lemans engine
had p-ports. The BSFC was better than anything
we have seen so far with side ports.

To answer your question... yes a butterfly will work
located in the plenum but the p-port engine will
idle like crap :)

Paul,

I thought the idea shown in the diagram of the NSU solution was appealing.
They had the primary peripheral port higher on the housing sidewall than the
secondary so the rotor at idle would have relatively more time to expel that
potentially charge-contaminating exhaust. Then, when the intake velocity is
stronger at higher RPM, the secondary opens up to provide more fuel.

Any idea how it well it worked? Did you ever hear an NSU at idle?

It's the same kind of idea as the guys who have proposed making a side port
intake for low speed and a peripheral port for high speed. I'm sure Mazda
must have tried that. Did they ever talk about it with you?

Barry Gardner
Wheaton, IL

As I recall you could not tell it was running :)
I drove an NSU RO 80 in Germany seven years ago with a similar
system and I was astounded how well it pulled away from a dead
stop. Not quickly but very smoothly. The RO80 TX did have a
a very inefficient torque converter. The owner of the car was
totally unaware that there were any problems with p-ports what
so ever. The RO 80 engine is larger displacement than
the Mazda but the rotor width was only 67 mm instead
of 80 mm however the rotors where much larger in diameter.
It was equivalent to about 4 liters in a piston engine I think.
Torque was a modest 117 foot pounds at 4,500 RPM and max HP
was 136 at 5,500 indicating it was severely breathing limited.
The intake runners were very long. My guess is close to 30 inches.
The RO 80 is not a small car and we had about 500 pounds
of passenger weight in the car. Both Juergen and I are
big people. The empty weight was 3000 pounds same as the RX8
without all the crash structural weight the smaller RX8 has.
Not much for such a large car.

Paul Lamar ...No rotor no motor.

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