I just found out there are 3 or maybe even more generation of UR crank pulleys. At least for the SR20. The first generation doesn't have holes in it. The older 2nd generations have holes in them but weighs over 2lbs while the newer 2nd gen has holes in it also but weighs 1lb 3.3oz. On the UR website, it says that only 15% of the hp gains are due to underdriving while 85% are due to weight loss. Is this true? So if two pulleys were the same size but one weights 1lb less than the other, then the lighter one will give an extra 2.7hp? That's what I got from UR's website and also, did you test your 6hp gain on the SE-R with the 1st, older 2nd, or newer 2nd gen? If it was the 1st gen ones u tested, it might be possible that the newest one mite free up to 10hp.
