Can't remember if you've already posted this verbiage...

Mazda Taiki
Mazda says Taiki's next-generation Rotary Engine 16X or "Renesis," a
1,600-cc (800 Ã? 2) powerplant with a new trochoid chamber shape,
boosts thermal efficiency and torque. These and other innovations help
make it a fuel miser. The shape change increases displacement. Still,
Mazda says the new engine is as compact and lightweight as the current
Renesis.

Lengthening the trochoid radius and eccentricity while making the
rotor housing narrower brought a longer stroke, thus shrinking the
combustion-chamber aspect ratio. And the surface area-to-volume ratio
of the combustion chamber dropped, limiting losses from cooling. The
smaller combustion chamber, the company says, promotes flame growth
for faster combustion and better fuel economy.

This is the first gasoline rotary engine developed to use direct-fuel
injection. The system inherits the basic design of the hydrogen rotary
engine, injecting gasoline in a high-pressure spray during the intake
cycle, promoting atomization and vaporization of fuel and formation of
a stable air-fuel mixture. The latent heat of fuel vaporization lowers
the temperature of the air-fuel mixture, thus raising the engine's
charging efficiency. At the same time, it reduces fuel adhesion to the
chamber wall â?? a problem for conventional port-injection systems â??
while promoting a more homogenous air-fuel mixture. This, in turn,
improves thermal efficiency and boosts torque.

Matt Prather

Matt,
While I agree with most of what you ( or Mazda) have stated, I can't for the
life of me understand how a narrower combustion chamber gives more efficient
flame front.

It is well known the piston ( round shape) gives the optimum flame front/
fuel burn as it radiates from the spark in an even distribution and there
aren't any squish areas some distance away ( as in a long flat chamber).

Paul has commented only recently that the more square rotor of the AIXRO go-cart
engine is second to the round shape of the piston- understandably!

Am I missing something here?

What is the definition of a combustion chamber aspect ratio?

George (down under)

You got me George :) Perhaps it got mixed up in the translation
from Japanese to English. The only thing I can think of is they did
it that way so the new engine would fit in the RX8 with a minimum of
changes in the engine compartment. I do understand the need for more
torque but they could have achieved the same result with a dual clutch
Formula One type transmission. The car would be more fun to drive.

Aspect ratio means length divided by width.