Rolf

OK Sorry. I did not know that about the German rating system.
You are right about the displacement. In Japanese terms the RO80
is a one liter. Smaller than  a 12 A with a 74 mm wide rotor.

Here is a shot of an RO80 rotor housing (I think) and 12A
rotor housing. Does that look like a RO80 rotor housing on
the left?

"The lower the R/E ratio and the narrower the piston, the higher the S/D
ratio becomes. It was for this reason that the piston width was kept
narrow. And it showed, fuel consumption figures were the lowest for
the EA 871."When Mazda goes to 100 mm wide pistons, the S/D will drop
to .296 or ~.30. In view of economy Mazda is going the wrong direction."

I agree with your numbers but I don't agree with your conclusion.
The BSFC numbers I have for the RO80 from Norbye's book  are no
better than the 13B. I think the 16B's better combustion chamber
shape will pay off. Time will tell.. that is if we ever get a chance
to measure it. There is also a question of how it was measured.
With "accessories" the RO80 engine was worse than the Mazda BSFC
wise by about .03. Namely .50 for the RO80 and .47 for the 13B.


"Maximum torque of the RO80 is 162 Nm which relates to a mep of
1.024 or 148 psi. The RX8 has some 160 ft lbs of torque which is
equal to 150 psi. Very close the same."

Here you are comparing apples with oranges. The RO80 is a p-port
engine and the RX8 engine is a side port engine. The 13B P-PORT
engine shows 200 foot pounds of torque.

"With a wider piston of 100 mm this number will drop."

I agree with this as the 100 mm wide rotor 16B side port area will
be the same as the 80 mm wide rotor RX8 side port area
despite an increase in torque. However that will definitely NOT be
the case with the 16B P-PORT engine. My guess is we will see
something like 300 foot pounds from the P-port 16B with a 3 inch
OD P-port runner.

We will probably also be able to work inside the engine without
taking it apart :)

BTW The EA 871 was not mentioned in the Norbye book. All NSU
engine numbers started with KKM. The RO 80 engine
was a KKM 612. The book was published in 1971. What years
were you there?

Also BTW It just dawned on me why Mazda did not do a turbo version
of the RX8. IMHO they are looking ahead to the 16B. Why spend the
money on a turbo when you will get the same performance
from a larger cheaper engine?

Paul Lamar ...No rotor no motor.

Thanks Paul for your comments.

Yes, the RO80 and the RX8 cannot be compared directly due to the
different ports and different aims. But then, one would expect
improvements over time and Mazda had more money to spent. As build then,
the two were not that far apart in top hp per displacement.

I agree, we have to wait and see how the 16B will turn out. It is not
always as it 'supposed' to be. In general, a larger surface area results
in higher consumption, but other factors have an impact as well. As you
said, the methods of measuring also differ, so an exact comparison is
not possible, looking in from the outside now.

Just like most people I too am looking forward to see the performance of
the 16B. You said it will be P-Port, that makes a lot of sense as the
side ports can not be increased by widening the rotor, but P-ports on
the other hand can be very large. Would you have any of your insider
knowledge as to when the 16B might be available in an RX-8, or is this
engine going into something else?

Obviously, Mazda is not willing to spend the money for a larger geometry
which would require new tooling. Widening the rotor is the easiest way
to increase displacement. We will see how it turns out. Regarding public
opinion, Mazda has to be careful not to build a dud. The relative small
HP of the RX7-8 compared to the big V-8's has often been a downer. I
hope it turns out right for Mazda. For a long time I had a 626, my son
now drives a Mazda 3, his first car. He likes it a lot.

Regarding the nice pictures you attached, the second one looks more like
the RO80 to my comprehension. It is such a long time ago. Comparing the
picture in the Wankel website, the first one on the left looks very much
like the EA871. Or it could be the EA866 which was supposed to go into
the RO 80 to get more HP. By that time, when this all happened I had
already left the company.
I think Norbye could not have included the EA 871 as I believe the engine
was developed after his book was released. Was it 1974 or 1975 when the
Norby book was published, or even before?

There was also the Ro135 a boat engine based on the 612 that was in the
RO80.
The EA871 was meant as a boat engine but was also used in the Fanliner
and Fantrainer for the German Luftwaffe. This engine was built more
compact, the center housing was reduced in width to make the crankshaft
shorter and stiffer. Water cooling was only applied on the hot section
and the cold section was no longer heated just to get faster warm-up.
With carburation, the EA871 had 170 HP at 6500 rpm and 212 Nm (156
ftlbs) at 4000 rpm. These numbers were not so great.

Further development was stopped when VW -Audi took over and had the say.
Mr. Piech, the CEO, and a member of the Porsche Families, was dead
against the rotary. That was unfortunate, as reliability had also
improved substantially by then. The housings of the EA871 were ceramic
coated for Gasoline as fuel, and for Natural Gas engines the housing was
coated with "Widia" a sintered metal used as cutting tool in Lathe bits.
The seals were a silicon-nitrate, and there were two seal in one slot.
The EA71 was used as well for experiments with hydrogen.

Manufacturing methods also improved. The piston was build-up not cast
which made it substantially lighter and cheaper. The side plates were
pressed in.

It is the old story, with enough time and money, the product gets better
and cheaper. Isn't that what you have been saying all along, especially
compared to the RPE.

Rolf

------------------------------------------------------------------------

"Yes, the RO80 and the RX8 can not be compared directly due to the
different ports and different aims. But then, one would expect
improvements over time and Mazda had more money to spent. As build then,
the two were not that far apart in top hp per displacement."

Yes but it is still apples and oranges. NSU did not have to put
up with draconian smog rules so a p-port was viable. A p-port is
not viable on the RX8 street engine for smog reasons
alone although I have an idea that might make it work :)
P-ports on a 13B are worth 50 HP at 7500 RPM and almost
100 HP at the RX8 red line of 8500 RPM on a 13B. I would say
only 60 HP over an RX8 engine. Lots and lots more over whatever
Mazda gets out of a 16B.

The largest problem with the Wankel engine is the combustion
chamber surface to volume ratio as far as thermal eff.
is concerned. Read BSFC. Much heat is lost to the cooling
system. This is bad for eff. but good in terms of pumped up
turbo charged power per cubic inch. The rotary will run at levels
that would melt a piston engine. 400 HP per rotor is common
and Abel Ibarra is working on 500 HP per 13B rotor.

A sphere is  perfect combustion chamber with the spark
plug located in the center. Max volume minimum surface area.

A round distorted short cylinder shaped combustion chamber is
next and is the norm in piston engines.

A short square box is next. Much like the AIXRO go cart
Wankel and the Norton Wankel to a lesser extent.
both of these engine are handicapped by either charge
cooling or air cooled rotors. The cooling blower is
consuming engine power in the Norton case.

The next best is the Mazda 16B rectangular box approaching
a square.

Next in line is the Mazda RX8 and 13B.

Perhaps the NSU RO80 engine and the Mazda 12A engine compete
for last place in the Wankel world combustion chamber competition :)