DEBOER@sbcglobal.net wrote:

Paul:
Here is an article I found on the web @
http://www.autoweb.com.au/start_/showall_on/id_MAZ/doc_maz0101101/article.ht
ml

New Rotary Engine Delivers Power, Fuel Efficiency

10 January 2001

By Haruo Okimoto, Manager, and Seiji Tajima, Senior Staff Member
RE Engineering Group, Powertrain Development Division

The RX-8 is built to accommodate Mazda's RENESIS rotary engine, an ideal
powerplant for sports cars. It is powerful, smooth, lightweight and compact,
and it has a low center of gravity.

"RENESIS," derived from the word "genesis," suggests the beginning of a new
type of rotary engine. Mazda's work on rotary engines began in 1961 and, six
years later, we introduced the Cosmo Sport, powered by the world's two-rotor
engine. Over the years, we made countless improvements. Today. The rotary
engine is used in the turbocharged RX-7 that we sell in Japan. Through 2000,
we have sold about 1.8 million cars rotary engine-powered cars.

The RENESIS is an advanced version of the MSP-RE concept rotary engine
featured in the RX-01 concept sports car exhibited at the 1995 Tokyo Motor
Show. This new-generation rotary engine was employed in the RX-EVOLV
four-passenger sports car shown first at the 1999 Tokyo Motor Show.

When developing the RENESIS, we aimed to retain power output on a par with
the turbocharged 13B-REW, the rotary engine that powers the RX-7, while
offering improved fuel economy and reduced emissions.

Side Intake and Exhaust Ports

Unlike previous mass-production rotary engines, which employed side exhaust
ports and peripheral intake ports, the naturally aspirated RENESIS has
intake and exhaust ports in the side housings. This configuration eliminates
overlap between the opening of the intake and exhaust ports, enhancing
combustion efficiency. The intake ports are 30% larger and their timing has
been changed to make them open sooner than in previous designs. Moreover,
the exhaust ports open later, resulting in a longer power (expansion) stroke
and providing radically improved heat efficiency.

At the same time, the RENESIS uses a six-port induction (6PI) design, in
which each rotor employs three intake ports, and a variable intake timing
mechanism. Under this system, dedicated high-speed intake ports begin to
operate when the engine operates at high-rev levels. This makes it possible
to use the intake's dynamic effect at high and low speeds to maximize
compression efficiency.

Unlike the single peripheral port per rotor of previous designs, the RENESIS
uses two exhaust ports per rotor. This produces a combined exhaust port
opening area nearly twice as large and results in a substantial reduction in
exhaust resistance.

The rotors have also been made lighter for better performance at high-rev
levels. The rotors used in the RENESIS weigh approximately 14% less than
those used in the engine that powers the RX-7, which we sell in Japan.

These enhancements provide high output rivaling the power of turbocharged
rotary engines with linear power characteristics from the low- to the
high-rev range.

Fuel Efficiency

The increased heat efficiency resulting from zero overlap between the
opening of the intake and exhaust ports makes it possible for the RENESIS to
run on a leaner fuel mixture than conventional rotary engines. When idling,
the RENESIS consumes 40% less fuel than the current production rotary
engine.

Reciprocating piston engines generally use a richer fuel mixture under
high-speed and high-load conditions to prevent knocking. In contrast, rotary
engines do not require a particularly rich fuel mixture under these
conditions due to their special combustion characteristics. In addition, the
RENESIS achieves nearly complete combustion over the entire speed range
thanks to its high compression ratio and the use of new fuel injectors
designed for improved fuel atomization. These enhancements allow the RENESIS
to run on a leaner fuel mixture than conventional rotary engines from the
low to the high-rev range. The result is the power and performance of a
sports car engine and reduced fuel consumption. Low Emissions

Due to their configurations, rotary engines produce less nitroxide (NOx)
than reciprocating piston engines, but they also tend to produce large
amounts of unburned hydrocarbons. The side exhaust layout used in the
RENESIS prevents unburned hydrocarbons of the combustion chamber housing
from escaping to the exhaust ports.

Instead, they are carried over and burned in the next combustion cycle,
dramatically reducing emissions. In addition, air injection directed into
the combustion chamber increases the efficiency of the exhaust reaction,
significantly over Mazda's existing system during engine startup. Together
with the double-skin exhaust manifold, the new layout makes the exhaust much
hotter when it reaches the catalytic converter, speeding the converter
reaction for clean emissions from the moment the engine is started.

Low Center of Gravity

With their low center of gravity rotary engines have an advantage over
reciprocating piston engines. We have exploited this benefit by using a
special oil pan configuration to make the engine's center of gravity even
lower.

Called the "wet sump" layout, it uses a baffle (dividing panel) within the
oil pan to prevent oil from collecting on one side during cornering. This
makes it possible to use a shallower oil pan. Mazda engineers also
experimented with "dry sump" designs, but they settled on the new wet sump
layout after considering weight, cost and the greater reliability of the
simpler system. The new oil pan is only about 40 mm thick, about half the
thickness of conventional designs.

Reduced Oil Consumption

In a rotary engine, oil is supplied directly to the interior walls of the
combustion chamber to lubricate the "apex" and "corner" seals. We've kept
the paths which supply oil in the RENESIS as small as possible, and we have
redesigned the oil supply nozzles to improve their efficiency. With these
enhancements, the RENESIS consumes about half as much oil as a conventional
rotary engine.

Superb Response and Sound to Thrill the Senses

The RENESIS achieves a sophisticated balance between high revs and high
output, on the one hand, and fuel economy and low emissions, on the other.
In addition, we are working to enhance the performance and to realize the
high degree of reliability and durability required in a mass-production
sports car. We want to achieve output of 250 horsepower.

Unlike rotary engines equipped with peripheral exhaust ports, the side
layout of the RENESIS produces clear, transparent high tones and powerful
low tones. We recognize engine sound as a key element in any sports car, and
we are working to ensure that the engine produces a satisfying roar as you
depress the accelerator.

All of us on the rotary engine engineering team hope you will have the
opportunity to experience the feeling that only the RENESIS can deliver. We
are dedicated to delivering an engine that will delight sports car
enthusiasts worldwide.

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
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