how do underdrive pullies work?
#1
02-20-2007, 12:53 PM
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#2
02-20-2007, 02:18 PM
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Less drag on the engine by turning slower.
Similar to taking the fan off and replacing it with Efans. Only downside to Underdrive pulleys is the slow down affects everything that runs off them. As a result your alternator puts out less.
In my experience I gained more with the Efan replacement over the underdrive pulleys. If you plan on doing both, do them at the same time and save yourself a lot of hassle. I plan on doing the Efan upgrade and keeping my pulleys stock. As for actual HP gain from underdrive pulleys, I think they say 5-15 HP.
Similar to taking the fan off and replacing it with Efans. Only downside to Underdrive pulleys is the slow down affects everything that runs off them. As a result your alternator puts out less.
In my experience I gained more with the Efan replacement over the underdrive pulleys. If you plan on doing both, do them at the same time and save yourself a lot of hassle. I plan on doing the Efan upgrade and keeping my pulleys stock. As for actual HP gain from underdrive pulleys, I think they say 5-15 HP.
Last edited by MI OFACE; 02-20-2007 at 03:21 PM.
#3
04-30-2007, 09:00 PM
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F150 Online Underpulley Discussion
Sounds like it is no noticeable advantage.
I think, like one guy said, spend the money elsewhere for mods such as a tuner, intake tc for more 'bang for the buck' performance.
Its not the weight of the puuley. It is the parasitic drain of power to turn the alternator, A/C, Power steering etc... A underdrive pulley will turn those others slower and means less power robbed from the engine.
I think one topic of pulley weight is responsing to rotational torque and inertia of turning those pulleys. I don't think that is a valid argument as much as the pumps and A/C system vs simply turnng a pulley.
Sounds like it is no noticeable advantage.
I think, like one guy said, spend the money elsewhere for mods such as a tuner, intake tc for more 'bang for the buck' performance.
Its not the weight of the puuley. It is the parasitic drain of power to turn the alternator, A/C, Power steering etc... A underdrive pulley will turn those others slower and means less power robbed from the engine.
I think one topic of pulley weight is responsing to rotational torque and inertia of turning those pulleys. I don't think that is a valid argument as much as the pumps and A/C system vs simply turnng a pulley.
Last edited by dennisfranz; 04-30-2007 at 09:06 PM.
#5
05-01-2007, 12:12 PM
waterman308,
Might you be hearing about a 12 lbs pulley and thinking about the weight of the actual pulley? If that is the case then what the weight designation is referring to a supercharger pulley and the amount of boost it will create if used. An under drive pulley as was explained reduces the power required to turn the accessories. What it entails is at least two pulleys, a smaller than original crankshaft pulley with a larger water pump pulley. While the power gains are minimal the increase in throttle response is what is usually most noticeable. The trade off is less powerful power steering and less current from the alternator at low rpms.
JMC
Might you be hearing about a 12 lbs pulley and thinking about the weight of the actual pulley? If that is the case then what the weight designation is referring to a supercharger pulley and the amount of boost it will create if used. An under drive pulley as was explained reduces the power required to turn the accessories. What it entails is at least two pulleys, a smaller than original crankshaft pulley with a larger water pump pulley. While the power gains are minimal the increase in throttle response is what is usually most noticeable. The trade off is less powerful power steering and less current from the alternator at low rpms.
JMC