Post by
Sentientbydesign »
https://forums.nicoclub.com/sentientbydesign-u25395.html
Mon Mar 10, 2008 5:55 am
The underdrive pulleys are smaller in diameter than stock, so you save weight and parasitic drag because you're feeding less than optimal rotation into each of the accessories (A/C, Alternator, power steering pump...etc).
The non-underdrive pulleys are stock diameter, but are built lighter than stock. This allows for optimal rotation on all of your accessories and a release of some unecessary rotational drag.
You'll have to verify that the crank pulley is well balanced because some have complained about their crank seals wearing prematurely do to vibration with the pulleys.
Also, I don't want to get into an argument with any other member about how underdriving is perfectly fine unless you're running a gigawatt or two. Nissan designed the pulleys at their diameter for a reason, let's keep it that way.