Hi was wondering if there is any adavatage to go with getting a crank pulley besides the little weight savings?
Does a 15% pulley with a 2% over crank pulley roughly equal the same as a 17% sc pulley by itself?

Not technically, but close...
But... I would stay away from the lightweight crank pulley (0% or +2%).

We always advise not doing a lightweight crank pulley.

But if you want to get to 17% on the supercharger just go with the 17% pulley as it will have the belts last longer and work better than 15+2 as that won't add up to 17 it's actually less.
https://www.waymotorworks.com/17-sup...ulley-wmw.html

but if you do want to end up with the 15 and 2%. Go with the ATI damper 2% as it is a real damper so it won't damge bearings or the oil pan.
https://www.waymotorworks.com/super-...ulley-r53.html

Thanks for the insight. I have no problem with going with just the 17% pulley.
why the hesitation with a light weight pulley though?

The point of the crank pulley (crank damper) is to absorb/dampen engine/crank vibration and harmonics........putting a lightweight one on there defeats the purpose of a damper. It's hard on your bearings and other components.

Just put a 17% pulley on the thing and be done with it. The reduction in belt life from a 17% pulley vs. 15% pulley is negligible to say the least. Unless you just want to spend the extra money....then put an ATI 2% under damper on there like WMS said.

I get 30,000 miles or more out of my SC belt (I run a 17% pulley) before it starts looking like it needs to be changed out. I could probably go much longer, but why risk it.

2%+15% = 16,67% SC pulley 1-1/(1,02x1/0,85)=0,1666...

My fault, brain fart on my part. Wasn't thinking about the harmonics that would be less asorbed by the lightweight crank pulley.