Supercharger Question

[FoLola]

The service manual states that under no circumstances should you run the supercharger more than idle speed without the hose connected to the carburetor. 

Any idea why that is? Maybe I damaged the SC while I was trying to figure out the poor running. (It turned out to be a failed intake manifold gasket. Someone used a felt gasket instead of steel.)

[mfg]

10 minutes ago, FoLola said:

The service manual states that under no circumstances should you run the supercharger more than idle speed without the hose connected to the carburetor. 

Any idea why that is? Maybe I damaged the SC while I was trying to figure out the poor running. (It turned out to be a failed intake manifold gasket. Someone used a felt gasket instead of steel.)

I always thought that advice, (or warning), had more to do with the large volume of air being blown around the engine compartment kicking up God knows what!....Not to mention the deafening noise emanating from an 'uncapped' blower!

I never understood why occasionally revving the engine with the carb hose disconnected while tuning would have any detrimental effect on the supercharger.

[brad]

From what I was told, It has to do with slipping of the drive element without a load on it. 

[mfg]

On 2/27/2020 at 11:31 AM, brad said:

From what I was told, It has to do with slipping of the drive element without a load on it. 

Yes, some back pressure on the impeller probably helps prevent slipping in the drive element, however, I'd still wear EARMUFFS!!

[silverstude]

I was told that back pressure on the impeller is required over a certain RPM or else it will cavitate, however I've never heard of an airscrew cavitating, only a boat propeller.  So, the obvious issue would be the internals.   I wonder if this ancient warning applies to the newer bronze  parts and higher pressure spring packs...