Overdrive Pulley ?????'s
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Teching In
Joined: Apr 2002
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Overdrive Pulley ?????'s Does any one know the difference between the overdrive and underdrive alt. pulleys. What are the typical power gains for each of them. I have also heard that the overdrive pulley is better for A4's. Any answers or advice will be greatly appreciated. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Teching In
Joined: Apr 2002
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From: End of North Star Dragway. . . literally.
Re: Overdrive Pulley ?????'s Have never heard of an overdrive pulley, but they do make underdrive pulley. The alternator pulley is not the pulley you want, your car will have serious charging problems. You want the underdrive crank pulley. Is said you can see a gain of 10-12 hp, and it helps throttle response a lot. I have one, and it helped out a lot after I put my cam in. Get the ASP pulley, all others have said to cause serious problems in engines.
TECH Addict
Joined: Dec 2001
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From: Fort Worth,TX
Re: Overdrive Pulley ?????'s </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 84ZZ4:
<strong>It would be nice if they did make an overdrive pulley for the alternator. That way people who had the underdrive pulley + charging problems could put that on to fix the problem.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">They do call thunder racing.ASP makes it.
<strong>It would be nice if they did make an overdrive pulley for the alternator. That way people who had the underdrive pulley + charging problems could put that on to fix the problem.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">They do call thunder racing.ASP makes it.
Teching In
Joined: Nov 2001
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Re: Overdrive Pulley ?????'s You are absolutely correct! I don't remember seeing that before, but hey...
I have an underdrive alt pulley which I've never installed. My charging is fine without it, not sure I want to try it. Unfortunately I really need to get the crank pulley only belts, since mine are a tad loose.
I have an underdrive alt pulley which I've never installed. My charging is fine without it, not sure I want to try it. Unfortunately I really need to get the crank pulley only belts, since mine are a tad loose.
Launching!
Joined: Dec 2001
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From: Indiana
Re: Overdrive Pulley ?????'s Just for my own clarification purposes...
Don't people typically put underdrive pullies on their car to eliminate parasitic loss from things like the alternator and accessories? If so, wouldn't putting an overdrive pulley on the alternator and/or accessories defeat the purpose of the underdrives? I'm no rocket scientist so please someone correct me if I'm wrong.
Don't people typically put underdrive pullies on their car to eliminate parasitic loss from things like the alternator and accessories? If so, wouldn't putting an overdrive pulley on the alternator and/or accessories defeat the purpose of the underdrives? I'm no rocket scientist so please someone correct me if I'm wrong.
Teching In
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Re: Overdrive Pulley ?????'s Putting an underdrive pulley on the crank frees up horsepower both by underdriving the accessories and by reducing rotating mass on the front of the crank.
Some people find that after doing this their alternator doesn't charge properly. If you then use an overdrive pulley on the alternator, it should more or less cancel out the underdrive effect on that accessory only!. You'll still be getting the horsepower increase from underdriving the rest of the accessories as well as the reduction in mass on the crank snout.
I'd also be willing to guess that of all the pulleys, the LEAST amount of HP is gained by underdriving the alternator.
Some people find that after doing this their alternator doesn't charge properly. If you then use an overdrive pulley on the alternator, it should more or less cancel out the underdrive effect on that accessory only!. You'll still be getting the horsepower increase from underdriving the rest of the accessories as well as the reduction in mass on the crank snout.
I'd also be willing to guess that of all the pulleys, the LEAST amount of HP is gained by underdriving the alternator.
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Re: Overdrive Pulley ?????'s If you use just the underdrive crank pulley, even on an A4, you should be fine. The only A4s I know who had problems used both underdrive pulleys and had a stock idle speed.
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