Noise Reduction Retrofit for a 'New Look' GMC Transit Bus: Service Bulletin

摘要

This document gives instructions on how to apply a noise treatment to a contemporary city transit bus without extensive structural alteration. Prototype anti-noise treatments of two conventional transit motorbuses were tested: a Flexible 'New Look' and a GMC 'New Look' model. Baseline bus configuration, noise ratings, and performance benchmarks are presented for a GMC model T8H-5307A transit bus, powered by a Detroit Diesel 8V-71N engine. Earlier, a Flxible model 111DC-D061 was similarly treated using the same concepts and much of the same hardware. The results are almost identical, showing the wide range of treatment applicability. This report gives instructions as to how GMC 'New Look' model is retrofitted with a turbocharged 8V-71TAC engine and ancillary hardware. The instructions include the revision of the engine aspiration system for easier breathing, the lining of the engine compartment with an anti-noise blanket, and the silencing of the hiss of the compressed air system dryer.