To get the  16X displacement and they also narrowed the rotor width.
They are doing that after finding out the flame
propagation does not get  all the way to the
sides when the width is over 75mm. The 13B is 80mm.

To increase  displacement from 1146cc (12A) which was 75mm wide
rotors, to about 1600cc the eccentricity and
radius need to be  increased. E of 17.5mm
and radius of 122.5mm which is up from 15 mm and
105mm. E17.5,R 122.5, W 70 gives 1560cc. E 18,
R 126, W 70 gives 1660cc.
Either would  increase torque and help the combustion efficiency.

Dale  Davies


  They did not try side by side plugs. Austro
engines has a wide  rotor withplugs side by side.

Paul Lamar

If you pushed the rotor  width to 80mm and dual s x s plugs with your
coils would give 3.6 to 3.8 liter displacement  with gobs of torque.
For  autos run lower  RIM for a bit better fuel economy.

 Dale Davies

 You mean wider than 80 MM right?
 The current displacement is 2,6 liters.

 For 3.9 it would be 120 mm  wide.

 Paul Lamar

The side-by-side plugs are  probably done for redundancy.
Mazda's  16X  paper describes the best width and length ratios  and
their  effect on flame speed.
When the flame front touches the side walls or
the adjacent spark plug's  flame front  it slows down.
The 12A has the proper ratio.  The 13 B does not.  As Dale Davies just
pointed out the 16 X would return to the proper ratio.

Barry Bordes

Do you have a scanned copy of that paper?

Paul Lamar


Paul, it is from a Patent 2009 0101103 0A1
attached in a word doc.

Barry Bordes

Thanks for the patent Barry. Too big to publish just yet. I'll
convert it
to a pdf and see if I can make it smaller.

No mention of side by side plugs nor are there any illustrations of
side by side by
side plugs in the patent.

The text runs on to pages and pages. It is an attempt to over whelm
the patent office with bull shit :-)

Super Tech in Germany has built some engines with narrower rotors.
I am surprised Mazda was granted a patent on it.

Here is a view of the Austro wide rotor.
Note the cooling fins inside the rotor. Will work real well with
the oil
squirter.  Here too is a picture of the Kantana powered with a 2 rotor.
Most of these picture were taken at the factory by Mark Wrathal
and myself.


Paul Lamar


This ignores the work Mazda did with the trailing and far trailing
plugs. That improved the LeMans engine efficiency enough to trade off
the complexity of the third plug. Perhaps it would work well with 2 side
by side and 1 trailing. Three plugs per rotor in a different way.


One of the SAE papers I read in the far past, and I don't have the
number at hand, was about work done on flathead engines. They have all
sorts of filling and pumping issues, but they were trying to improve
torque by higher and higher compression. They found that at a specific
clearance head-to-piston the fire just goes out. In the SAE tests I
recall the magic clearance varied between .010 and .015 inches depending
on plug placement and mixture. I have always wondered if the rotary
could improve efficiency by raising the center depression, (some), and
tapering it all the way to the sides of the chamber and lengthwise to
the tip seals.

This would be hard and expensive to machine, but with modern Laser
sintering techniques it could be done fairly easily. (Pat. pending) The
narrowing of the 16B chamber and eccentricity increase strike me as only
to improve torque for automotive use. The Mazda comment about not
burning to the side of anything wider than the 75mm width could also be
a result of the close fit of the flat sides outside the of the center
depression. The LeMans engine seemed to address the close or quench area
question with the far trailing plug.

I know Mazda had done a lot of studying of the center depression. This
helps spread the flame front at the expense of compression. Modern
direct injection engines are using higher and higher compression to
improve efficiency. It is tough to get much over 10:1 in the rotary with
the current depression. I believe that the shallow, but all over
depression could improve the flame front while at least maintaining the
current C.R.. I lack the money to try it, but a test could be done and
at the same time it would be possible to sinter a lighter than iron
material for RPM potential.

Bill Jepson


It would appear that Austro do not use ‘leading and trailing’ plugs,

just 'side by side'.

Dave Mccandless in Oz

NSU RO80 built 1967 to 1977 was a beautiful car. The engine was like a 10A for displacement. Single plugs. They never did get the apex seals figured out like Mazda did so engine life was a detriment. Saw one in Edmonton, Alberta years ago. Looked real good. Not many around.
Dale Davies

I drove one in Germany. Great car. It had 4 p-ports. Big ones and little ones.

Paul Lamar

It is too bad they could not overcome their apex seal issues. Definitely a more luxurious car than the Mazda of the time. At 115HP from a 2.0L engine at that time was fairly good.
Today it would be a 3.0L to 4.5L two and three rotor Audi autos.
Dale Davies


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