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 with    plugs 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


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