APS pullies....simple question..... I hope
Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,009
Likes: 1
From: Springfield MO
APS pullies....simple question..... I hope
I'm looking into a crank pulley from asp. I notice that it retains full charge at 750 rpm. But, if you purchase the alt pulley with it, full charge at idle is increased to 950 rpms....why is that? Will the underdrive pulley on the alt help ET. I always thought that putting the pulley on the alt. would help charge at lower rpms, but I guess it does just the opposite.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: APS pullies....simple question..... I hope (AS84)
A 20% underdrive crank pulley is 20% smaller in diameter than stock.
If you leave the stock alt pulley it will run 20% slower and can leave to charging problems at idle with full accessories on.
If you put a 20% smaller in diameter pulley on the alt, the alt will spin at stock speeds and there will be no charging issues at idle.
If you put a 20% larger in diameter pulley on the alt, the alt will spin 40% slower and will definitely lead to charging issues at idle.
So look to the relative size of the alt pulley to know the results.
If you leave the stock alt pulley it will run 20% slower and can leave to charging problems at idle with full accessories on.
If you put a 20% smaller in diameter pulley on the alt, the alt will spin at stock speeds and there will be no charging issues at idle.
If you put a 20% larger in diameter pulley on the alt, the alt will spin 40% slower and will definitely lead to charging issues at idle.
So look to the relative size of the alt pulley to know the results.
