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The audible noise characteristics of direct injectors are important to OEM customers when selecting a high pressure gasoline fuel injector. The activation noise is an undesirable aspect that needs to be minimized through injector design, injector mounting, and acoustic treatments. Experimentally identifying the location and frequency of noise sources is beneficial to the improvement of injector designs. Acoustic holography is a useful tool in locating these noise sources by measuring a sound pressure field with multiple microphones and using this field to estimate the source location. For injector testing, the local boundary conditions of the noise source will affect the resultant sound field. Therefore, how the injector is mounted within the test fixture will change the resultant noise field measured. In this study, the process of qualifying an acoustic holography fixture using measurement system analysis for GDi fuel injector testing will be documented.

Gasoline Direct injection (GDi) systems offer performance and /or fuel consumption advantages compared to the traditional lower pressure port fuel injected technology. One disadvantage of GDi is the higher level of audible noise produced by the high pressure GDi system components. Powertrain noise is a known warranty complaint across the automotive industry. This paper presents an objective comparison of acoustic noise emitted by eight solenoid actuated fuel injector designs during their normal operation, including at engine idle, where powertrain noise is more noticeable to the customer. Taguchi Robust Engineering methods will be used to conduct an assessment of the noise generated by various GDi fuel injector designs. Injector fixturing, measurement procedures, and their impact on reducing test-to-test measurement variation are discussed.