Some of your numbers are off. You have: Stock Crank Pulley : 74mm S/C - - Ratio = 2.0270, this ratio gives stock crank pulley at 150mm, but stock pulley is 155mm, so 155mm/74mm = 2.094 Ratio.

That changes some of your numbers.

So for a stock 155mm pulley, S/C pulley would need to be reduced to
64.4mm to equal the boost of 178mm Crank Pulley running @ 6,200 Engine RPM (155mm/2.4054 = 64.4mm)
63.4mm to equal the boost of 181mm Crank Pulley running @ 6,200 Engine RPM (155mm/2.4459 = 63.4mm)
62.0mm to equal the boost of 185mm Crank Pulley running @ 6,200 Engine RPM (155mm/2.5000 = 62.0mm)

This also means Stock Crank Pulley (155mm) would need a 51.6mm S/C Pulley for MAX supposedly safe S/C RPM (18630 S/C RPM) (155mm/3.005 = 51.6mm where 3.005 = 18630RPM / 6200RPM).

To reach this MAX "safe" S/C RPM:
178mm Crank Pulley would need a 59.2mm S/C Pulley
181mm Crank Pulley would need a 60.2mm S/C Pulley
185mm Crank Pulley would need a 61.6mm S/C Pulley

Now, as of right now, we don't have the actual size of Code3's S/C pulley, but he posted over on mbworld that "...the new sc pulley is no more than .5" smaller than the stock one". 0.5" = 12.7mm -> Stock S/C pulley: 74mm - 12.7mm = 61.3mm for Code3 (again, NOT the official size as of this posting. Hasn't been officially announced yet. I'm just using this number as the SMALLEST size to expect). That puts their pulley maximally at 0.3mm SMALLER then what you want for a 185mm Crank Pulley for your max safe S/C RPMs. Their S/C pulley would put you at 18,711 S/C RPM @ 6200RPM and 21,140 S/C RPM @ 7000RPM (for a ratio of 3.018 = 185mm/61.3mm)

After all those calculations, it looks like 10% under max S/C RPM may not be a good idea, See this thread: talking about 192mm crank pulley

A 192mm Crank pulley gives:
192 Crank Pulley : 74mm Stock S/C - - Ratio = 2.594
Engine RPM @ 6000 - - S/C RPM = 15564
Engine RPM @ 6200 - - S/C RPM = 16083 - Rev Limiter W/Tune
Engine RPM @ 7000 - - S/C RPM = 18158

He was getting detonation at WOT with that pulley and no tune, so 15,564 S/C RPM is too much for the fuel system at WOT. This is REALLY close (64 RPM) to a 185mm pulley running at a tuned 6200 RPM (15500 S/C RPM)

Brian, you haven't had detonation at WOT with the 185mm crank pulley, have you? I don't remember reading anything saying that you had.

Assuming you haven't, that tells us that things start to go bad with a ratio somewhere greater than 2.5 (185mm crank pulley/74mm stock S/C pulley = 2.5) and less than 2.594 (192mm/74mm=2.594)

Crank Pulley / Code3 S/C Pulley (at guess of .5" smaller then stock):
155mm/61.3mm = 2.528
178mm/61.3mm = 2.904
181mm/61.3mm = 2.953
185mm/61.3mm = 3.018

So the numbers say their S/C pulley should NOT work well with anything but the stock crank pulley.


Now, Brandon did say that his pulley dyno'ed a bit less then the 185mm pulley. From the numbers above, the S/C pulley needs to be 62.0mm to equal the 185mm crank pulley ratio. 74mm - 62.0mm = 12.0mm -> 12.0mm/25.4mm per inch = .47inch, really close to .5". So we now know that their pulley CAN'T be 61.3mm and has to be bigger then 62mm (equivalent to 185mm crank pulley) and less then 63.4mm (equivalent to 181mm crank pulley).

So if we use 15500 S/C RPM as the max safe RPM @ 6200 engine RPM (Ratio = 2.5) this assumes 185mm crank pulley produces max safe S/C RPMs:

178mm Crank Pulley would need a 71.2mm S/C Pulley
181mm Crank Pulley would need a 72.4mm S/C Pulley
185mm Crank Pulley would need a 74.0mm S/C Pulley

So you can't use their S/C pulley with any after market crank pulley.

Of course, my math could be wrong...