EXTREME ACOUSTICS ⊲
The Noise, Vibration, Harshness( NVH) Semi Anechoic room is the heart of acoustic development. It’ s quiet in a way that most people never experience. Foam about 18 inches thick pad the walls, and are wrapped in a honeycomb expanded mesh. The wall panels absorb sound while the floor reflects it. Rotax uses this room to measure and identify the entire acoustic nature of the engine, isolating it from other parts such as exhaust or intake noise. The insulated shaft, attached to the crankshaft, connects to the asynchronous measuring machine placed in a separate room. A hemispherical microphone array surrounds the engine at specified distances to measure the frequencies and amplitudes of all sound-emitting sources.
Throughout iterative prototype development, an engine will be placed in the room several times to target specific component sound signatures. By covering the entire engine with acoustic sound barrier material, then removing one piece of insulation to expose an engine part( such as the coil pack), repeating the test, then removing another chunk( over the air silencer, for example), Rotax discovers how each component contributes specific decibels to the overall setup. Even after the start of production, the team will bring serialized additional engines into the chamber to reanalyze and continue improvements.“ Bad” noises are captured and potentially mitigated, and“ good” tones get curated into Ski-Doo’ s desired engine sound.
⊳ INJECTOR FLOW BENCH TESTS
The flow test machine is an invaluable tool to keep high-tech fuel injection systems well-tested and operating at peak. Rotax utilizes a flow-bench test cell to routinely cycle its direct injectors and obtain massive samples and data sets in a very short time. This cell houses six injectors pulsed at more than 7,000 RPM for hours or even days – equating to millions of pulses gathered for data analysis. Fluid is pumped to each injector cavity, and then the injectors are cycled using Rotax’ s spec electronic signal structure that specifies duration, pressure or cycles per minute. With this information, engineers can isolate an issue, test changes made in the production process or analyze a new component.
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JANUARY 2026 / SNOWGOER. COM / 41