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Old 03-28-2010, 02:22 AM   #8 (permalink)
Red Lion
EcoModding Lurker
 
Join Date: Jan 2010
Location: Missouri
Posts: 65

Serenity - '93 Nissan Sentra SE-R
90 day: 20.55 mpg (US)
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I would guess your MPG will increase in the sub 1mpg range. I doubt you'll see the cost come back in gains for a VERY long time, especially considering how light your stock pulley is (my 240sx's OEM pulley weighs about 9lbs compared to an Unorthodox 1.5lb pulley; now that's some weight loss).

The performance you'll mostly see in a lightweight pulley, which most people buy them for, is engine response, which I guess in a round-about way increases MPG because the engine doesn't work as hard to turn it's rotational parts. However, I never liked underdrive pulleys and prefer stock-size pulleys that are lightweight AND harmonically dampened (which 99.9% of aftermarket pulleys aren't).

Though I have heard some people say that using a lightweight (or underdriven, I can't remember) pulley on the A/C decreases power lost during A/C usage, so I guess that kind of increases MPG while running the A/C, but I don't have any first-hand experience.

Quote:
Originally Posted by Piwoslaw View Post
Why are underdrive pulleys so much more expensive than OEM pulleys? Smaller production volume? Lightweight, hi-tech materials? An underdrive pulley is smaller, so it requires less material, and so would be cheaper and lighter.

Just my common sense.
Simply put, because it's a "performance" mod and can be sold as such. I'm sure the automakers have good reasons for not using aluminum pulleys too (maybe fatigue?).

Quote:
Originally Posted by greasemonkee View Post
Might buy a set of rod bearings to go with your underdrive crank pulley, especially if the factory had an isolator in the oem unit.
Since he's probably not going to be spinning the engine to the upper RPM's often (I'm guessing), he probably won't have to worry too much about that.
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