Whats the difference between Unorthodox overdrive and underdrive crank pulleys?
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From: Stockbridge, GA, US
Whats the difference between Unorthodox overdrive and underdrive crank pulleys?
This may come off as a stupid question but im just curious. What do they exactly do? Nobody has ever told me what exactly underdrive and overdrive do. I have heard that underdrive is a good thing, but now I see a new Unorthodox crank pulley, its the RC overdrive race pulley. Anyone heard or running this pulley? Just something I have been thinking about...TIA..... 
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From: ???????
Re: Whats the difference between Unorthodox overdrive and underdrive crank pulleys? (TeamTooQuick)
i would assume that an overdrive pulley would supply more power to the accessories such as power steering or water pump...
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Re: Whats the difference between Unorthodox overdrive and underdrive crank pulleys? (TeamTooQuick)
Underdrive pulleys spin your accessories (alternator, ps, etc.) at a slower speed. That way they take less power.
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From: Mustafar
Re: Whats the difference between Unorthodox overdrive and underdrive crank pulleys? (J337_UNIT)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J337_UNIT »</TD></TR><TR><TD CLASS="quote">i would assume that an overdrive pulley would supply more power to the accessories such as power steering or water pump...</TD></TR></TABLE>
The "overdrive" pulleys are intended for supercharged applications, in which case the pulley spins the SC faster, thus creating more boost.
The "overdrive" pulleys are intended for supercharged applications, in which case the pulley spins the SC faster, thus creating more boost.
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Darth ModerVader
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From: Mustafar
Re: Whats the difference between Unorthodox overdrive and underdrive crank pulleys? (TeamTooQuick)
The RC "overdrive" pulley, as I stated above, is intended for supercharged applications. It drives the alternator (and thus the supercharger) at a higher rate, resulting in increased boost levels.
"Underdrive" pulleys drive the alternator and accessories at a reduced rate, lessening the parasitic drag on the engine. In other words, the engine doesn't need to work as hard to turn the accessories, so more power is freed-up.
Keep in mind that a large portion of the "gains" produced by UR crank pulleys are not the result of underdriving, but are instead a product of the reduced mass of the pulley itself. This is why you'll typically see better gains from the UR pulley compared to a setup that uses the stock crank pulley and underdriving accessory pulleys, even if the accessory pulleys are driving at an equal, or even lesser rate than with the UR setup.
"Underdrive" pulleys drive the alternator and accessories at a reduced rate, lessening the parasitic drag on the engine. In other words, the engine doesn't need to work as hard to turn the accessories, so more power is freed-up.
Keep in mind that a large portion of the "gains" produced by UR crank pulleys are not the result of underdriving, but are instead a product of the reduced mass of the pulley itself. This is why you'll typically see better gains from the UR pulley compared to a setup that uses the stock crank pulley and underdriving accessory pulleys, even if the accessory pulleys are driving at an equal, or even lesser rate than with the UR setup.
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