The new RX-8, as mentioned, as powered by a 1.3 liter RENESIS dual rotary
engine. This engine, unlike a standard piston controlled combustion system
does not use a system of valves and pistons within the engine to introduce
the flow of air and fuel into the engine for the combustion process, but
instead a system of triangular rotors that spin within the engine housing.
Instead of valves that open and close to let in the air and fuel, as well as
to release the exhaust from the cylinders, this engine does not have valves.
As the rotor spins in the housing, the direct intake and exhaust ports are
controlled by the motion of the rotor blades against the housing as it moves
through the 4 steps of combustion. The air and fuel enter the chamber, and
at that point, the engine is at it's first step. The rotor then pushes the
air and fuel to the second step, the compression step. Once the air and
fuel have been compressed, they are moved to the section that contains the
spark plugs, and there the third step of the process takes place, which is
detonation, and from there, the rotor enters the exhaust port area, which is
the fourth and final step of the rotor combustion process. One advantage of
this engine style is that with fewer moving parts, there are less parts to
fail, and with the lack of connecting rods, this engine is able to build
it's power at a very high RPM range, and redline on the new RX-8 is an
astonishing 9000 RPM.
This new RX-8, when equipped with the four speed
electronically controlled automatic transmission the RENESIS rotary builds
an impressive 197 horsepower at seventy-two hundred RPM and 164 pound-feet
of torque at five thousand RPM, but when the six speed manual transmission
is chosen the horsepower jumps to 238 at eighty five hundred RPM, although
the torque output drops to 159. The increase in power between the two
transmission options is thanks to the addition of two extra intake ports to
the engine fitted up to the manual transmission. The engine builds this
power by means of a ten to one compression ratio, with the air intake being
controlled by the variable dynamic effect intake system and the fuel
provided by means of Mazda's electromagnetic fuel delivery system, and the
spark is provided by a pointless electronic ignition system. This engine is
water cooled, and the cooling effort is assisted by the dual engine oil
coolers. Exhaust is moved away from the engine by means of a single exhaust
system which vents out of the back of the car via two exhaust outlets
mounted opposite each other on the lower corners of the rear fascia. The
power of this new wonder is put to the ground by means of one of two
transmission options, as previously mentioned. Those transmission offerings
are the four speed electronically controlled automatic transmission, or the
6 speed close ratio manual transmission.
Along with the manual
transmission's higher output engine, it also features a lower gearing which
boosts low end acceleration, and the overdrive styled sixth gear allows for
smooth highway cruising and helps to support the fuel mileage. The
automatic transmission has less low end gearing, but the engine with the
automatic transmission offering has more torque, which helps the low end
acceleration, yet still keeping the mileage high, even with only 4 gears.
The power is then shipped from the transmission to the rear differential by
means of the lightweight carbon fiber driveshaft, which holds up just as
well as a metal driveshaft, but the subtracted weight allows for less
parasitic loss common with rear wheel drive vehicles. All of the new RX-8's
come with a steep final drive ratio of 4.44 equipped with a limited slip
differential, and regardless of the transmission chosen, the average RX-8
driver can expect about eighteen miles per gallon around town, and twenty
four or twenty five miles per gallon on the highway.
