That is only for the trailing plug Skip.
  There must have been something else going on with the Rotamax.

  Paul Lamar


 Thanks Skip...no doubt about the factor of the apex seal going by the
 spark
 plugs.I remember at some point one of the Mazda factory guys in the early
 1990's telling us they dealt with this factor when they did the three
 sparkplug modification for the four rotor LeMans project.They were using
 castings with an additional sparkplug above the two original sparkplugs to
 address the highly quenched trailing end and its poor flame propagation,
 they made the plug hole as small as possible.It demonstrably worked to
 address fuel consumption byburning some of the fuel that was before simply
 going out the exhaust pipe.

 But having said that, the leakage was clearly
 evident because while it actually improved fuel consumption, the
 volumetric
 efficiency of the engine dropped according to the Mazda folks.About the
 simplest way they addressed the high-to-low pressure area flow was to keep
 the plug hole as small as possible.For our application of the engine to
 sustained high power settings involved in aircraft use, at this point in
 development and using proven technologies, it seems the three sparkplug
 approach with this small hole would work well to substantively address the
 issue of this highly inefficient and quenched area in the combustion
 chamber.

 But Mazda is driven by the automotive production market and it is
 clear they ran the numbers and more cost-effective to develop the two
 sparkplug side port RX-8 to reduce the overlap and improve BSFC for road
 cars.Just wonder whether deep in the bowels of Hiroshima whether a group
 of people have, or arepresently working to save this little engine by
 experimenting with more than one option, includingUncle Paul's turbo
 compound ideas.If not, it is because their hands are tied financially by
 short term cash flow and profitabilitythreatening car companies.The
 Mazda organization has some amazing, smart folks who remain inspired by
 their rotary "father", then later Mazda Chairman Yamamoto.It seems they
 must have already, or are currently exploring the TC option to see what it
 could hold for this little engine by putting to work that unusually high
 amount of energy going out the exhaust pipe.

 Meanwhile, absent any major
 changes in design, we know a three sparkplug approach works to improve the
 burn and improve fuel mileage.Yasuo Tatsutomi told Yoshinori Honiden they
 had to reduce fuel consumption 10-15% to win LeMans with an rpm band that
 could range from 6,000-9,000.To do that with a standard, homogenous charge
 engine is like climbing Mt. Everest. They simply could not have done it
 without those rotor housings.Even with them, the LeMans drivers had strict
 orders from Yoshinori Honiden to lift and early/coast at the end of the
 straight and soft pedal through the corners.The primary goal was fuel
 savings but it was also easier on the engine heat flux.In this respect
 they even went from black to silver paint on the upper engine cowlto
 address temperature issues.

 The previous year the ceramic exfoliated inside
 the engines. Aircraft race duty cyle is harder--no lifting at the end of
 the straight stretch and going into corners-- and we are attempting to do
 that using what are basically warmed over, off-the-shelf production parts
 for grocery getters.That is a serious challange no matter how we slice it.
 But in the words of Nobuhiro Yamamoto (he headed up the third gen RX-7
 engine development),after the LeMans effort,"We can no longer say we
 share major components between the production and racing rotaries.But we
 are still a very close bunch--the rotary people!"A rotary brother indeed.

 -
 Steve Beckham

Steve,
I was wondering if it might not be easier to go the opposite way and put a
sufficient depth recess in the rotor ( perhaps a high compression rotor), in
the squish area leading to the larger rotor depression. It may not have to
be very deep or wide, perhaps a couple of mm deep and 1" wide.
I don't know how that would affect the compression and power, but it might
solve the unburned fuel issue.
Just a suggestion.
George (down under)

It has been tried George. You saw it here a few months or maybe years
ago. It may have been on the Norton before the Midwest and now
well before Diamond took over.

Paul Lamar