Exhaust System Design

Silencer System Design

Experimental Testing

A variable length diffuser chamber was used to find the best chamber design to attenuate

the Polaris 440 engine.   The same technique and lessons learned will be applied to the

Polaris 600cc engine. .                                                                                                                                               

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From the testing on the Polaris 440 cc engine, SPR learned that a 6" and the 5" silencers can be placed in series to minimize exhaust noise in chosen strategic frequencies.

purple - 6" DBa level                                                                                                                                        

orange - 5" DBa level

yellow - DBa without silencer

Mathematical Modeling of the 600 cc DI Engine

Numerous models were used to estimate the engine's highest strongest frequencies that attribute its total sound intensity.  Additional mathematical models were used to determine the best diffuser chamber lengths to target the engine's strongest frequencies.   

Modeling the frequency attenuation of a typical single chamber diffuser.

The first iteration silencer for the 600 cc DI engine was created combining an absorption silencer and a dual stage diffuser.  Combining the results of the modeled diffuser chambers and a proven high frequency noise absorber our silencer solution was finalized.  The SolidWorks design and first iteration silencer are shown below.

Expansion Chamber Design

Catalyst Design