Eric_Oz_S2

Anyone know what the exact crankshaft pulley dia is on an S2 that drives the alternator? I could measure it I know, but I will need to remove the belts first.

Thanks

Eric

HJK

5.34 inch sounds ok?

Dubai944

Its too small for decent supercharging, I know that

Eric_Oz_S2

I think it is around 5"/127mm measured to the bottom of the grooves.

Anyone know for sure.

Eric_Oz_S2

In the case of The Rotrex, that isn't necessarily the case due to the high internal gearing ratio (9.5 or 7.5). It is quite easy to spin these to get 20psi using the standard crankshaft pully.

Eric

Dubai944

In theory. In practise belt slip is your enemy and with a 6 rib 5 inch crank pulley the charger pulleys on any supercharger are just too small for big boost. Fine if you are sticking to the typical 5-7psi range you probably won't even notice, but 20psi? Would love to see that

Eric_Oz_S2

Point taken. The Rotrex have 8 rib belt pulleys. So perhaps OK with a custom 8 rib 5 inch pulley. And yes you may as well go bigger in that case since it will be the same cost.