Development of the J2825 On-Highway Motorcycle Sound Test Procedure 2011-01-1614
In response to a growing need for a practical and technically valid method for measuring exhaust sound pressure levels (SPL) of on-highway motorcycles, the SAE Motorcycle Technical Steering Committee has developed Surface Vehicle Recommended Practice J28251, “Measurement of Exhaust Sound Pressure Levels of Stationary On-Highway Motorcycles,” which includes a new stationary sound test procedure and recommendations for limit values. Key goals of the development process included: minimal equipment requirements, ease of implementation by non-technical personnel, and consistency with the federal EPA requirements; in particular, vehicles compliant with the EPA requirements should not fail when assessed using J2825.
Development of the recommended practice involved a comprehensive field study of 25 motorcycles and 76 different exhaust systems, ranging from relatively quiet OEM systems to unbaffled, aftermarket exhaust systems. For the various motorcycle/exhaust system configurations, SPL measurements were made using the EPA pass-by procedure and several different stationary measurement methods. Correlations between the results obtained by these different methods were studied for the entire subject group (combinations of motorcycle and exhaust system) as well as for sub-groups based on motorcycle engine configuration.
Of the stationary measurement methods explored; the most reliable results were obtained when the SPL was measured 20 inches from the tailpipe outlet. On the basis of engine configuration, stationary test results were correlated with results measured using the wide-open throttle, EPA pass-by procedure. For four-cylinder motorcycles, the best correlation was obtained at 5000 rpm; for all other engine types the best correlation was obtained at 2000 rpm. Satisfactory results were also obtained using idle SPL measurement.