Within the PNGV program, very challenging targets in respect to vehicle fuel economy were set. These could not be met with today's gasoline engines and driveline concepts. One possible alternative approach is a hybrid vehicle with a small displacement engine that exceeds the fuel economy of conventional engines: the 1.2L DIATA (Direct-Injection-Aluminum-Throughbolt-Assembly) engine.
Within the development of a CIDI engine the NVH aspects are of particular importance as the customer (i.e., driver) should not notice any negative difference to gasoline engines. Therefore, gasoline engine transparency in respect to NVH was one primary goal within the development process.
This paper describes the implementation of NVH features into the engine design already in the initial concept design phases, and the consequent NVH optimization throughout the development phase. Using FE-based dynamic structure evaluations, the critical engine components (e.g. engine block, cylinder head, covers) were NVH optimized even before the first prototype was built. This ensured that only NVH refinement measures were required in a further prototype phase.
NVH measurements of the prototype engines verified the excellent NVH characteristics of the DIATA engine, making it a best-in-class engine. The target of gasoline transparency was achieved.