Switching Pulley on Alternator

[GCAdidas13 10+ year member]

well how does the crankshaft diameter matter?

in my car, on the dash the car idles at 700 RPM and i have straight power from the battery

at 900-1000RPM the alternator kicks on and my lights get brighter and my voltage goes up to 14.4v...

so the rotational velocity of the alternator has to increase by 200RPM, or 30% or so.

 

[Moe Lester 10+ year member]

my crankshaft pulley is ~6" diameter(couldnt measure completely accurately in the space but its pretty close to 6) and my alternator pulley is 2"

"HA

so i was" is what i was referring to, he agreed that your calculations were correct, sorry for the confusion //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif no real point in arguing, we both agree with each other haha.

anyways, @ GC

say youve got a 4" diameter crankshaft pulley and a 2" pulley on the alternator, 4/2 = 2. the alternator spins twice as fast as the engine does. if your engine is at 700, the alt is at 1400.

 

[GCAdidas13 10+ year member]

But again, though...

in my car, on the dash the car idles at 700 RPM and i have straight power from the battery
at 900-1000RPM the alternator kicks on and my lights get brighter and my voltage goes up to 14.4v...

so the rotational velocity of the alternator has to increase by 200RPM, or 30% or so.

 

[Dustin07 10+ year member]

In Sport Truck mag last month they did an article that included how to, and why to install a smaller pully on the alternator... for the truckers with high demanding stereos.

just thought i'd mention it, a person could check out the site or look for last months mag on a stand somewhere, might give a little insight for a person who doesn't understand whats going on here...

//content.invisioncic.com/y282845/emoticons/angel.gif.fa7795fff6653f4381ba158c55a48b74.gif

 

[ngsm13 5,000+ posts]

I'd try to get a 5" cranshaft pulley, and a 2" alternator pulley. Should solve all your problems. And get another yellow top //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

NG

 

[GCAdidas13 10+ year member]

I'd try to get a 5" cranshaft pulley, and a 2" alternator pulley. Should solve all your problems. And get another yellow top //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
NG

would a 5" crankshaft pulley also throw off the other things that the crankshaft moves? like AC, etc...

 

[Moe Lester 10+ year member]

would a 5" crankshaft pulley also throw off the other things that the crankshaft moves? like AC, etc...

Depends what size your current crankshaft pulley is, maybe it is 5" already lol. If its smaller than 5" everything will spin faster, if its larger than 5" everything will spin slower

 

[GCAdidas13 10+ year member]

What all is affected by this? AC/Alternator for starters, what else?

AC will run faster meaning more HP taken from the engine for AC...

 

[Moe Lester 10+ year member]

anything that the belt drives, AC, Alt, fan (maybe yours is electric.. i dont know), water pump, power steering, and whatever else youve got on your car.

 

[audiolife 5,000+ posts]

you would be overdriving it though not under driving only way i see you hurting the car is if you constantly drive 120 mph just my take. never thought about the crank pulley good eye moe

 

[ngsm13 5,000+ posts]

you would be overdriving it though not under driving only way i see you hurting the car is if you constantly drive 120 mph just my take. never thought about the crank pulley good eye moe

Hey FOO! I'm the one who told him to get a slightly large crank pulley and slightly smaller alt pulley //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

NG

 

[audiolife 5,000+ posts]

moe eluded to it well before anyone else did lol i knew they made UNDERDRIVE crank pullies never thought of the overdrive lol. i know they use smaller alt pullies on underdrive cars that have stereos and alot of gus change pullies for spl purposes. did you happen to email norris adidas? i know he was on termpro earlier and i know he would know how to make it work better he is mechanically a very sound source for info like that lord knows he has done enough of it and 6 years ago when i worked with him he was smarter with most cars than most mechanics were lol. no joke