Side Exhaust Port System Rotary Engine Development
Seiji Tashima(Mazda Motor Corp.),  Suguru@Fuse(Mazda Motor Corp.), Ritsuharu Shimizu(Mazda Motor Corp.), Shinji Kanbara(Mazda Motor Corp.), Shinya Ueki(Mazda Motor Corp.)

Structure of the side exhaust port system Rotary Engine (RE) was theoretically expected to deliver low fuel consumption.  However, in order to address issues in production, the engine's internal structure was modified and fuel system was changed.  In addition, the intake and exhaust systems were developed such that the engine would be able to make most of the advantageous characteristics of the structure of exhaust emissions and engine output.  As a result, production of the new generation RE was realized that satisfies both environmental requirements and marketability.  During the development of this technology, compatibility with the hydrogen fuel was improved, which will contribute to the future hydrogen society. 

Previous RE had an issue with combustion stability during idle operation.  This drastically restricted improvement of the fuel economy and exhaust gas, which was a large roadblock to the evolution.  The technologies described below addressed this issue and evolved RE's major performances at the same time.
As Fig. 1 shows, previous RE used combination of the side intake port and the peripheral exhaust port, which created overlap of the exhaust stroke and the intake stroke.  This caused poor combustion stability, blocking improvement of the RE fuel economy.  The newly developed side exhaust port RE was geometrically able to avoid this overlap, but still remained overlap with clearance on the rotor side face.  Therefore, cutoff seal was newly developed.  The seal drastically improved the major issue of combustion stability at idle operation, delivering 20% of fuel economy improvement.  The side exhaust port also enabled reduction of the RE's largest exhaust emission of unburned hydrocarbon by 30% and the increase of the intake port area by 30%.  Compact module variable intake mechanism was developed that carefully used dynamic effects of intake air.  This realized extremely high intake charging efficiency at wide engine speed range, evolving to high density engine. 
@As a result of this development, improvement was made to the engine's basic performances of fuel economy , exhaust emissions and maximum output.

@The newly developed RE was introduced to the Japanese market in April 2003 followed by the USA and European markets.  57,480 units of RE had been produced as of the end of December.  It is likely that the RE will drastically exceed the annual production plan of 60,000 units.  Expectation of the new RE is growing around the world.


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