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Discussion Starter #1
what are these underdriver/overdrive pulleys for this car, and what do they do?
Are they just lighter? would i be better off changing the flywheel first
and do these make a big difference?
 

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Vidfinnx said:
what are these underdriver/overdrive pulleys for this car, and what do they do?
Are they just lighter? would i be better off changing the flywheel first
and do these make a big difference?
An "underdrive" lightweight crank pulley is smaller in diameter in addition to being made of a lightweight material. Therefore, aside from the weight savings, the pulley doesn't spin the accessories as fast as a "fullsize" lightweight or regular crank pulley. By not wasting as much energy on spinning accessories, more is available to be put to the ground. An "overdrive" alternator pulley compensates for the "underdrive" lightweight crank pulley's smaller diameter by assuring that the car's electrical system receives full charge (like stock) instead of a reduced power charging state like when an UD crank pulley is used with the stock alternator pulley.

Can't speak on their effectiveness as a performance mod, though until feedback on long term use is available, please realize that you may be risking premature failure of your crank shaft due to lack of a harmonic damper.
 

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Vid, honestly, SEARCH before you begin making posts like these again. There are dozens of threads on this exact issue. In any case, Get 1T Done is correct, and I can vouch for the effectiveness of an aftermarket pulley.
 

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Discussion Starter #4
Bosco said:
Vid, honestly, SEARCH before you begin making posts like these again. There are dozens of threads on this exact issue. In any case, Get 1T Done is correct, and I can vouch for the effectiveness of an aftermarket pulley.
well i have been searching, but i just keep finding them for sale LOL and they are pretty cheap
 

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GET 1T DONE said:
An "underdrive" lightweight crank pulley is smaller in diameter in addition to being made of a lightweight material. Therefore, aside from the weight savings, the pulley doesn't spin the accessories as fast as a "fullsize" lightweight or regular crank pulley. By not wasting as much energy on spinning accessories, more is available to be put to the ground. An "overdrive" alternator pulley compensates for the "underdrive" lightweight crank pulley's smaller diameter by assuring that the car's electrical system receives full charge (like stock) instead of a reduced power charging state like when an UD crank pulley is used with the stock alternator pulley.

Can't speak on their effectiveness as a performance mod, though until feedback on long term use is available, please realize that you may be risking premature failure of your crank shaft due to lack of a harmonic damper.

Im a little confused by this you say a smaller pulley would not spin the accessories as fast. Shouldnt a smaller diameter pulley have more revolutions than a larger pulley due its size? Thus this should spin your accessories faster no? Thanks.
 

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I thought so too, but I read an article (somewhere, sorry don't remember) that explained it. The smaller pulley has a smaller circumference than the larger pulley, so essentially "pulls less belt through it" than a larger diameter pulley in one revolution. So the belt doesn't spin as quickly as it would with a larger pulley.
 

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minato said:
I thought so too, but I read an article (somewhere, sorry don't remember) that explained it. The smaller pulley has a smaller circumference than the larger pulley, so essentially "pulls less belt through it" than a larger diameter pulley in one revolution. So the belt doesn't spin as quickly as it would with a larger pulley.
Correct....
 

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And is it true that these only really benefit N/A setups? Why is that?
 

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hey man, i think they also benifit FI guys, but it will make you push more psi and if you dont have a built motor then your asking for problemsi could be wrong, im planning on installing my SFR UD pulley next weekend
 

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Think of it this way - an underdrive pulley is spinning everything slower. If you're supercharged, you're spinning the supercharger pulley slower, therefore creating less boost. That's why some boosted guys on here have overdrive crank pulleys. Faster spinning creates more boost.
 

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So im just thinking this though. It's forced induction related but the mod is N/A and this is the right thred so bear with me. Once I build my engine I'll boost it up some more. I have a SDS so to get stage 2 im gonna put a smaller pully on the SDS shaft. Then for an effective stage 3, I would have to have an overdrive crank pully as well as the stage 2 pully on the shaft. My questions is since im upping the Uverdrive crank pully would i wanna change all of my accesery pullys(a/c, power stearing, waterpump...) to a bigger pully as well to bring each accesory pully back to stock? I understand that there will be a (rap load of power to compensate for it but is it worth it? Whats everyones views?
 

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minato said:
I thought so too, but I read an article (somewhere, sorry don't remember) that explained it. The smaller pulley has a smaller circumference than the larger pulley, so essentially "pulls less belt through it" than a larger diameter pulley in one revolution. So the belt doesn't spin as quickly as it would with a larger pulley.
Ahhh, basic math. I'm glad SOMEONE figured it out.





BESIDES ME AND MOST 3RD GRADERS!!!!!!!
 

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What answer do you want? Yes, they do make a noticeable difference in the car's performance in 1st and 2nd gear. An underdrive pulley has a larger effect than a fullsize lightweight pulley because, while both are lightening the rotational mass of the crankshaft, the underdrive pulley lets the rest of the accessories spin slower, which means more power is taken advantage of by the crankshaft to the wheels.

Changing the flywheel is something along the same general lines, but a little more radical. A crank pulley install takes maybe half an hour if you have any mechanical experience and the tools for the job. A flywheel install takes hours and very good automotive knowledge. The flywheel has a more drastic effect because the weight difference from stock to aftermarket is greater than the crank pulley's weight difference from stock to aftermarket. Also, an aftermarket flywheel is about five times as expensive.
 

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Carrera1984 said:
So im just thinking this though. It's forced induction related but the mod is N/A and this is the right thred so bear with me. Once I build my engine I'll boost it up some more. I have a SDS so to get stage 2 im gonna put a smaller pully on the SDS shaft. Then for an effective stage 3, I would have to have an overdrive crank pully as well as the stage 2 pully on the shaft. My questions is since im upping the Uverdrive crank pully would i wanna change all of my accesery pullys(a/c, power stearing, waterpump...) to a bigger pully as well to bring each accesory pully back to stock? I understand that there will be a (rap load of power to compensate for it but is it worth it? Whats everyones views?
This is what I was thinking.... i dono what i should do,,,
 
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