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 newly developed V1505-CR-T engine is not only small displacement of 1.5L, but also four-cylinders, and it is low vibration in addition compactness and lightweight. However, the bore of this engine is smaller than other similar displacements, because it is the unique four-cylinders. It was modified to DI (Direct-Injection) for the first time at this displacement, and common rail system was adopted. By applying Center-Direct-Injection-System, in which the injectors are arranged vertically at the center of combustion chamber, it was possible to inject fuel uniformly. Therefore, air and fuel are easily mixed even in small bore and small combustion chamber. Furthermore, Intake and Exhaust system were changed from two valves to four valves to intake more air. Regarding the concern that these modifications may increase engine dimensions, the exhaust emissions reduction device was specially designed, and we realized compactness and lightweight by new built-in arrangements such as the EGR (Exhaust Gas Recirculation) gas route into cylinder-head and the oil separator for the breather into cylinder head cover. In this article, we introduce techniques to comply with EU StageV on small bore engine and small combustion chamber.