"peripheral port right from the get go" begs the question: Since the
p-port
provides so much extra power, why doesn't Mazda use them?  Does the BSFC
suffer or is there something more important?  In any case the compound
turbine will more than make up for any possible loss in BSFC!

Norm

Mazda used them in the Lemans engine and got a BSFC of .47. That is
about the
lowest ANYBODY has been able to attain out of a
Wankel rotary so far and they were not running it super lean. They won
the race
outright in 1991 over all on a race fuel limit running against who's
who in
international car racing. ONLY Japanese company ever to win Lemans.

Mazda current rotary engine development is primarily driven by two
things.
Low speed/RPM torque and emissions. Low speed/RPM torque is the only
reason
for the extremely complicated RX8 engine intake manifold. P-ports are not
the best for low speed/RPM smooth running and emissions.

Paul Lamar

Unlike previous models, the RX-8 engine has no ports on the perimeter.
The side intake and exhaust ports on the RX-8 are likely a contributor
to the flooding problems. No port on the perimeter to sling the excess
liquid out of.

One would assume that the apex seal lube oil, injected from the
perimeter, behaves in the same way. This would reduce the amount of oil
in the exhaust, and also the amount needed to be injected. Thus, the
hydrocarbon emissions would be reduced. I'd guess this is the motivation
to move the exhaust ports to the sides.

The P-port would allow the apex lube oil to sling out. You would
probably need to inject more, and more would get entrained in the
incoming air. If true, this would increase hydrocarbon emissions.

I wonder what would happen if you were to move the ports to the
perimeter on an RX-8 engine.

Bill Dube'

Mazda wrote an SAE paper on the side port engine.

Shimizu, Ritsuharu et al. "Characteristics of fuel consumption and exhaust
emissions of the side exhaust port rotary engine"
Proceedings of the Future Transportation Technology Conference and
Exposition, Costa Mesa, CA, USA. Futuristic Concepts in Engines and
Components SAE Special Publications n 1108 1995. SAE, Warrendale, PA,
USA. p 181-188   SAE 950454.

It is not so much the lubricating oil that is the emissions problem.
It is the over lap between intake and exhaust that destabilizes
combustion at low speeds causing the engine to misfire at low RPM.
Every Mazda engine from the beginning would miss
fire periodically at idle with the results of a huge dollop of unburned
hydrocarbons went out the exhaust.

The RX8 engine is remarkable in the fact that it can pull away from a
stop without your foot on the accel pedal by merely releasing the clutch.
In other words it pulls from low RPM without stumbling. Not very fast
I might add.

Paul Lamar ...No rotor no motor.

Hello


The ex Mazda engineers I spoke with (who were in charge of improving the
BSFC of the rotary engine) said from their perspective the RENESIS engine
was designed for reducing emissions at idling speeds and city driving.  We
have to remember the side port exhaust was only part of the solution or one
of their goals so to speak.  The side port engine has a lot of advantages in
the automobile of which Bill has mentioned a few. They had a lot of R&D
work to do on changing the water passage configurations and controlling  the
heat flow dynamics to the side housings.  It was this research that was
deemed critical to the success of the RENESIS. In other words, the dog leg
in the exhaust path was needed to keep the exhaust port area hot. Some guys
are grinding these ports straighter so they can power attach a  turbo
charger to the engine.  I believe this will change the heat flow dynamics in
a negative way somewhere else.

It has been my experience meeting and speaking with about 7 Mazda rotary
engine engineers that there is a lot of disagreement about rotary engine
design even among dedicated ranks..

I finally understand why.  It is the same for us. First we have to
understand our needs and type of flights we will be doing.  What it the
goal?  Best BSFC?, lightest weight? best power?  the most inexpensive way? I
will have to say all around the PP engine is good if you need/want more than
250 HP out of the engine and can deal with the  robust exhaust.  For 180-200
Hp any number of NA combinations are adequate.

P-porting the RENESIS engine sounds good on paper but suddenly we are
coupling a very efficient intake port to a restricted exhaust port. Why do
it unless we need another research project to keep ourselves busy:) The
better question would be who has done it? It has been proposed for the last
three years now on different web discussion groups but I have still not
found any evidence of a PP RENESIS having  actually been tried.  Perhaps in
Australia, N.Z. or Puerto Rico where their our many racers.

We have a good example of a well thought out PP N/A engine already. The
Lemans engine with variable length manifolds.

I was told this engine could be tuned to achieve 0.46 lbs/hr/hp.

Doug in Japan



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