HOLD ON! THE NUMBERS BELOW MAY BE TOTALLY WRONG! THEY ARE BASED OFF A STOCK CRANK PULLEY BEING 150mm. IT MAY BE 155mm!
I need to find out for sure. ANYONE HAVE ONE LAYING AROUND THAT THEY CAN MEASURE?
Thanks to those that chimed in with the correct crank pulley measurements below. Stock Crank pulley is 154.4 mm. Info below is corrected for this.
I really doubt there's room to do a 62mm. The inside diameter of the pulley is 51.8 mm and you need 3.6 mm (on each side) for grooves. That only leaves 1.5 mm of material (on each side). That sounds pretty thin to me.
Here's some useful numbers to keep in mind:
Originally Posted by BrianBrave Corrected
By my calculations: (based on the stock 74.2 mm S/C Pulley)
Stock Crank Pulley (154.4 mm) : 74.2 mm S/C - - Ratio = 2.0809
Engine RPM @ 6,200 - - S/C RPM = 12,901
178mm Crank Pulley : 74.2 mm S/C - - Ratio = 2.3989
Engine RPM @ 6,200 - - S/C RPM = 14,873
181mm Crank Pulley : 74.2 mm S/C - - Ratio = 2.4459
Engine RPM @ 6,200 - - S/C RPM = 15,124
185 Crank Pulley : 74.2 mm S/C - - Ratio = 2.5000
Engine RPM @ 6,200 - - S/C RPM = 15,458
Using a Stock Crank Pulley, the S/C pulley would need to be reduced to:
64.4 mm to equal the boost of 178mm Crank Pulley running @ 6,200 Engine RPM
63.3mm to equal the boost of 181mm Crank Pulley running @ 6,200 Engine RPM
61.9mm to equal the boost of 185mm Crank Pulley running @ 6,200 Engine RPM
So if Eurocharged can make a 63 mm SC pulley, that would be slightly better than the 181 crank pulley. If they made a 62 mm SC pulley, that would be slightly worse than the 185 crank pulley.
Also, I wonder what would happen if we removed the clutch system from the pulley and machined the shaft down a little. That would allow for a smaller SC pulley, but what would it do to your low RPM performance? Would the ECU freak out or what?