Cause
| Correction
|
Whine
|
- Whine noise is typical of all superchargers and is not a reason to replace the supercharger or other components.
- Supercharger whine, inherent to the Roots design, results from eight pulses per engine revolution, 2:1 drive ratio x 4 lobes. Air induction system structure and acoustic resonators are designed to minimize whine.
|
Whistle
| A whistle noise is generated by tooth contact of the spur gears between the rotors. For instance, a low level whistle may occur at 2,300-2,800 RPM at 80 percent load driving up a very long grade. Although most of these conditions are
addressed by sound path isolation to the passenger compartment, some can still be heard by a very critical ear.
|
Supercharger rattle - growl
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- Supercharger growl may be heard at low speed or idle, with the engine under light load.
- Minuscule crankshaft speed variations, influenced by the torque converter, transmission, drive shaft, differential, and tires, are transmitted through the flexible drive belt to the supercharger. Operating in very thin air, the rotors oscillate and
cause the load to alternate from the drive to driven sides of the gear teeth, even precision parts have operating clearances. The entire supercharger drive system is tuned to minimize this noise.
|
Internal isolator
|
| • | The supercharger incorporates an internal isolator between the pulley and the rotor shaft, which has two functions. The first is to minimize a knocking sound when the engine is turned off and the mass of the supercharger rotor set is suddenly jerked
to a stop. And second, the isolator is tuned to minimize the normal engine firing pulses passed on to the supercharger rotor drive gears. It is active only in an unloaded condition, low engine speed point where boost is not requested. |
| • | If the engine or one of the components in the driveline is not operating to design intent, the isolator may make a harsh intermittent rattle sound that often goes through cycles as the engine speed or other conditions change slightly. |
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