Underdrive Pulley

The gains from this mod are SKEPTICAL to say the least. I didn't feel any gains from it...in fact I feel a little bit of loss at high rpm. I expected good gains on the upper end. But the gains from this mod may be better for you depending on your setup.

The reason I did it was because I had no access to a turbo in any junkyards close by and I haven't had luck getting parts from other people (having people go to junkyards for me). Nissan wanted $140 for their turbo crankshaft pulley and Unorthodoxracing was (is?) offering thier Turbo underdrive pulley for only $120. I really should've held off for a turbo pulley from a junkyard, but oh well.

All I can say is that I didn't feel any difference and if its really underdriving my accesories, then it seem to give me more of a loss (in upper-end RPM) than a gain (in HP). However if you are going to do a turbo conversion or Maxima alternator switch you need to get a crankshaft pulley w/one serpentine pulley slot and a serpentine water pump pulley. I would definately suggest finding these parts in a junkyard...if they'll let you strip them from the engine...not too likely. Here's the pic...it looks really good, but big deal if it doesn't perform for you.

There may be a reason I didn't feel any gains. I converted to an electric fan a couple months before putting in the Underdrive Pulley. The fan conversion is a great mod...helped me hit 60 in second (hitting 6K rpm without much trouble). But then my stock alternator went out (it was already on its way out). I converted to a Max. alternator, which means I had to convert my pulley system to accomodate for the serpentine pulley (didn't want to swap out my alt. pulley). So I bought a Turbo water pump pulley and the Underdrive Pulley. It's now hard to get to 6K, but still easier than before. Whereas I felt the car had a second wind at 5K up to 6K, now it only goes from about 5K to 5.5K. It may be that the Max. alternator takes away more HP than the Underdrive Pulley frees up, therefore a loss instead of a gain. So the Underdrive pulley may still be helping quite a bit. Most people who have them have no complaints and claim a significant gain, but many of those people haven't gotten rid of their fan clutch either...underdriving that beast has to help a lot...taking it off completely would help even more.

I have my doubts that the underdrive does that much. Plus, the main pulley driven elements are the Fan Clutch (which is the worst HP stealer) and the Alt. The AC and Power Steering Pump only take HP when they are being used, which you won't be using when dashing off the line or getting a dyno. SO the alt. and fan clutch are the main components you are trying to Underdrive. Since the fan was already off, only the Alt. was really stealing HP, and since I upgraded it, this may have made the difference. SO maybe the Underdrive pulley is worth it, maybe it's not...but it is surely aethestically pleasing.