Cog drive belts for superchargers are loud, we all know that.

So why are cog driven timing belts quiet? What's the difference?

Mods, feel free to move this to another section if needed.

 

Because they are smaller in size, the grooves are smaller.. I am pretty sure most of the noise comes from the air that is pushed out of the grooves..

 

I've replaced many a timing belt, but never had my hands on a ProCharger or Maggie cog drive to compare it with. I've seen plenty of pics.... and some pulleys had holes drilled in the bottoms of the cogs to "let the air out", but I didn't realize they were bigger cogs.