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· Administrator
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Most use 10" = 10#s. But those numbers are so arbitrary as to be near useless. It is always best to talk about pullies using ratio rather than #s of advertised/expected pounds of boost. Some manufactures purposely run slightly bigger that their competitors to make it seem their product is better. It is not. It is simply increasing ratio. (This response is not necessarily to the OP as I am quite sure he is fully aware of this info. But it is good for others reading the thread)

Jim
 

· Just a farm truck
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1,512 Posts
My JLP one piece was less than 10" edge to edge (~9.8" if I remember correctly). The thing with the JLP one is that it doesn't have a deep lip like the metco does. To get an accurate comparison, you really need a large enough caliper to span the width and measure the valley of the ribs across the midsection of both pulleys.
 

· Panty Dropper
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5,913 Posts
Most use 10" = 10#s. But those numbers are so arbitrary as to be near useless. It is always best to talk about pullies using ratio rather than #s of advertised/expected pounds of boost. Some manufactures purposely run slightly bigger that their competitors to make it seem their product is better. It is not. It is simply increasing ratio. This response is not necessarily to the OP as I am quite sure he is fully aware of this info. But it is good for others reading the thread)

Jim
Agreed, but I think it's safe to say that he was specifically referring to the size of a 10lb lower, which is it's common name regardless of how much boost you actually see. A 10# lower stops being that when you have a different upper pulley, which is what you were referring to.
 

· Administrator
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Agreed, but I think it's safe to say that he was specifically referring to the size of a 10lb lower, which is it's common name regardless of how much boost you actually see. A 10# lower stops being that when you have a different upper pulley, which is what you were referring to.
Not only changing ratio via upper pully. Also with airflow changes whether intake or exhaust. Or extreme like cams or porting. And any combination of these listed. Add to that aftermarket blowers and the basic terminology really gets silly. Ratio works across all platforms and combinations.


Formula for circumference of a circle is:

C = 2(pi)*R

where C is circumference and r is radius. We can measure the circumference with simple tools like string and tape measure. or ruler. Then calculate diameter(which is twice the radius) by dividing the circumference by Pi(3.1416 for this level of needed accuracy)


Jim
 
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