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The latest frequency-conversion system, as typified by inverter power generator, is capable of providing superb fuel economy and NVH characteristics by means of real-time control of the engine speed according to its load condition. The current mechanical governor, however, can difficultly achieve that demand of performance. In order to meet these requirements, we have developed the electronic governor system having high control flexibility and response for small diesel engines for agricultural and industrial use. In developing this electronic governor system, we have adopted a method that can minimize modification of current engines. We have successfully developed the electronic governor system by means of a post-assembly installation, in which dedicated functional devices are installed to complete engine while keeping intact the current highly reliable PFR type fuel-injection pump and the mechanical governor.

Off-road engines are requested with limited space due to variety of end products, and it is also requested reasonable costs for the limited end products prices. For that purpose, several small off-road engines have to comply with emission legislations by only engine modifications. However, the additional engine control and devices (=High pressure direct injection, combustion chamber modification, electrical control, turbo charging control, etc.) must be expensive, and increasing the total engine costs and manpower for developments. These are very critical issues for long term possibility of same engine productions which cover to new legislations in each country. Thanks to drastic fuel condition improvement for passenger cars / trucks around the world, it would be aroused one of the best solution by DOC (Diesel Oxidation Catalyst) systems rather than the engine modifications.

Recently, EU StageV emissions regulations have been enforced in the European market since 2019, increasing environmental requirements for diesel engines. EU StageV has been tightened compared to EPA Tier4 regulation, which demand PM (Particulate Matter) reduction and added new PN (Particle Number) regulations. Until the previous regulation EU Stage IIIA, the power category of 19kW or more and less than 37 kW had adopted mechanical IDI (Indirect-Injection). This mechanical engine is characterized by compactness and lightweight because of simple structure. Therefore, this engine is appreciated by customer with easy installation. On the other hand, to achieve EU StageV, it is necessary to adopt the electronic direct injection common rail system with more precise fuel injection and advanced exhaust gas aftertreatment device.

The New Kubota Grand L30 Series Compact Tractors are powerful, user-friendly compact tractors that have advanced functions to provide the maximum performance. Many new features such as IntelliPanel enable users to obtain high workability, comfort, and operability. IntelliPanel is an advanced function that displays information on a liquid crystal display to help users' with operation and maintenance. An electronically controlled multi-gear GST (Glide Shift Transmission) enables users to choose gears for 12 travel speeds using one lever, during travel without operating a clutch. An ECU (Electric Control Unit) controls solenoid valves and a proportional reducing valve to allow for smooth gear changes.

In this paper, the features of V3300 heavy-duty diesel engine series and the technologies to achieve the concepts are introduced. V3300 series is the vertical water-cooled 4 cycle IDI diesel engine for agricultural and industrial use. Its output is the highest in our company's IDI diesel engines. V3300 series was developed based on the concepts of our conventional series (low vibration, low noise, clean exhaust emissions and good fuel efficiency). V3300 series adopts 3 valves system for the first time in agricultural and industrial diesel engines. This 3 valves system is composed of 2 intake valves and 1 exhaust valve per cylinder. V3300 series also adopts the new combustion system which succeeded to the KUBOTA's original combustion system. The volumetric efficiency, the fuel efficiency and the exhaust emission performance are improved by these systems. The comfort level is achieved by reduction of the vibration and the noise by adoption of the built-in balancer.