You got me...Paxton's site say 17psi. Perhaps they think it maxes at 13 because of the pulley (3.0)...you can get a crank pulley for even more psi. Using the crank pulley would reduce overspin issues with the blower itself.

I just know there is no difference with 1220 and 1220SL...besides the self lube.

 

3.0 SC pulley looks to start overspinning the 1220 at around 8000-8500 (there's an exact calculation to determine it somewhere around here), but the crank pulley should mitigate that. That's what 518355 (sp? ) did to get around 18psi.

 

^^^ That doesn't sound right to me thinking about it, yes you can change the crank pulley size to get more psi or less depending on what you want to do, same as the blower, but the blower pulley and crank pulley are combined, there is no reduction gear or trans in between. If you alter the crank pulley size to reduce over spin on the blower then you are simply reducing the blower speed/psi. Your effectively canceling one out for the other. All you have is a choice and the primary way is the blower pulley way, do both if you run out of pulley on the blower, gives you more options to turn up the speed/psi on the blower, but doesn't reduce over spinning going with one vs the other for a set psi level.

Explain to me if I'm missing something here

 

SC rpm = (crankshaft pulley size / sc pulley size) * engine rpm
For instance:
5in/3in = 1.67 -> 1.67 * 8500 = 14167 SC rpm
4in/3in = 1.33 -> 1.33 *8500 = 11305 SC rpm

It seems to me that by combining the two measurements as a ratio you can maximize boost and minimize overspin of the SC. There are a few sites that exemplify this in their kits...they give the ratios and boost levels to help people decide what to get without creating SC problems. You can calculate the ratios to verify that you're not overspinning the blower.

I'm not sure what the SoS crank pulley's size is vs stock but if you knew you could work the ratio vs. SC pulley to max psi and min overspin. Hope that helps.

 

my bad than....

 

I've never been in a FI S but I fail to understand how you guys put down all this power?

 

I'll take you for a ride sometime, Barry. Really, the way a supercharged S makes power traction isn't too much of a problem as long as you have sticky tires.

 

When you say a smaller crank pulley, are you talking about the actual engine crank pulley or the pulley for the supercharger belt that bolts to it?

 

Hells yea man.

 

I would assume the larger pulley for the blower belt, not the serpentine belt.