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Over the past year, research was completed to determine a method and process by which ORV sound level emissions could be more closely monitored. A static or stationary test will be used on all types of ORVs. Noise levels will be checked from a twenty- inch distance from the exhaust pipe at half the vehicle's rated revolutions per minute (RPM) or as detailed in the automotive specifications SAE J1169, March 92 or SAE J1287, June 86. The maximum noise level permitted under these testing conditions will be 94 dBa which is the current limit set by the Off-Road Recreation Vehicles Act of Part 811 of 1994 PA 451 (MCL 324.811). All vehicles will required to have a muffler and spark arrester containing baffles that can be confirmed by inserting a flexible, plastic rod.
Generally speaking, the guidelines for testing at "half the rate RPM" will be based on some vehicle similarities. In most cases, full-sized vehicles with "V" configured engines will be tested at 2,500 RPM and all others at 2,000 RPM, which was a method developed and used while testing these vehicles at Silver Lake back in 1997. Most reverse flow mufflers will meet the spark arrester requirements, as will most turbochargers. However, straight-through mufflers, such as glass-pack designs without baffles and mechanically driven superchargers, do not qualify as adequate spark arresters.
Motorcycles and ATVs will be tested like the full-sized vehicles by placing a sound meter at a forty-five degree angle, twenty inches from the muffler exhaust pipe. In most cases, 80 cc engines will be tested at 6,000 RPM, 125 cc at 5,000 RPM, 250 cc at 4,000 RPM and 500 + cc at 3,000 - 3,500 RPM. The Motorcycle Industry Council produces a manual detailing the standards ATVs and motorcycles must meet. A muffler that meets the Environmental Acoustic Reduction (E.A.R.) standards may be considered as a viable solution for motorcycles. Most ATVs with unaltered, factory equipped exhaust systems, that have been properly maintained, will meet the requirements. Those vehicles that have been manufactured for "closed track" use only, such as many motocross or "dirt-bike" motorcycles, will most likely not meet the requirements. This is also often true where after market installations have altered the original exhaust system in attempts to gain additional horsepower.
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