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Lets talk dual altenators again.

Big to small = faster. The crank\waterpump are the drive and need to be bigger than the alt. If the water pump is 6" in diameter and the alt is 3", it will take twice as many turns of the alt to match the waterpump. In one full turn a 6" pulley moves 18.84" (2*3.14*3) of belt, in one full turn the 3" pulley moves 9.42" (2*3.14*1.5) of belt, so for them to be equal (a must be in a belt/gear drive system) the little pulley will have to spin twice to move the full 19" of belt.
 
smaller than drive pully=spins faster=overdriven i thought, but when they talk about increasing the boost on a blower they use a larger pully though right? man im confused /forums/images/graemlins/screwy.gif
 
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Big to small = faster. The crank\waterpump are the drive and need to be bigger than the alt. If the water pump is 6" in diameter and the alt is 3", it will take twice as many turns of the alt to match the waterpump. In one full turn a 6" pulley moves 37.68" (2*3.14*6) of belt, in one full turn the 3" pulley moves 18.84" (2*3.14*6) of belt, so for them to be equal (a must be in a belt/gear drive system) the little pulley will have to spin twice to move the full 37" of belt.

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I don't know why you have that two in there??
The equation is: (pi)(diamter) or (2)(radius)(pi)

You have it as (pi)(2)(dia) which is 2 times too much
 
Thanx, I was thinking I was using the radius when I did them. Fixed now.
 
No, that was in response to overdriving the alternator. The amount I was able to "overdrive" the alternator with the smaller pulley wasn't enough to make a difference in voltage worth the effort, at idle.

I measured an older alternator in my garage I have since that pulley swap, and it is much smaller than even the overdrive pulley.

I think this extra small stock one would provide enough RPM's at idle to solve the low voltage issue. Just can't use it since I'm now semi-serpentine.
 
What kind of pulley are these coming with? I *think* GM went with a 6 groove on the full serpentine setups, but I'm curious. Just wonder if anyone has a serpentine alt pulley laying around that might be smaller than what I've got, and be the right # of grooves.

I actually haven't tested this setups output at idle, it seems better than the v-belt setup with the lights and all, but the difference between idle and off-idle is noticeable still.

I'm still surprised this 78amp handles the two stock fans and EFI, even if the difference is noticeable.
 
One part of this I don't get is the voltage regulation. If you put two alts on, each will have it's own voltage regulator. If both charge the same battery bank it seems to me that both regulators would see the voltage of the other alt. Which each would 'think' is the voltage of the battery bank. That sounds like you'd get a no charge condition unless there were only one regulator controling both alts.
 
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BTW, I have a strike capaciter wired in with my amps if that matters. /forums/images/graemlins/dunno.gif

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Good thing i read through the majority of this thread before posting..
I was gonna say you need a capacitor if your headlights are dimming and your batt voltage is dropping when your stereo hits hard..
Is it a .5 or a 1 ferad capacitor you got?? How many peak watts total?

/forums/images/graemlins/dunno.gif

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I thik it's 1 ferad. It's an audiobahn cap and the guy that installed my system said it was big enough. /forums/images/graemlins/thinking.gif
 
First off, Bobby, your a dumb ass. You dont need two alternators. Everyone knows you can just bolt down a gas powered generater in back, this is called a SPLIT system. Just route your outgoing generator power directly to the battery cable,the negative one. This way it will make you go faster, and give you tons more horsepower,and remove the need to get and aftermarket mallory ingition. Just fill it up the same time you fill up your truck. And It will be really loud, (supposed to be that way),,,,,,just roll down the windows so the smoke dosent fill up the cab, and crank up the tunes. This is good to wire directly to your stero amp as well. Also, at christmas time ,,,you can run a bunch of cristmas lights on your truck (the flashing ones) to be more decrotive. You can also mount Santa on top of your truck to match. I hope this helps. /forums/images/graemlins/screwy.gif
 
depends which one you are talking about
drive or driven
most of us are refering to the driven one on the alternator
 
Most over drive pulleys are designed for high RPMs and low drag (spin fewer times per crank revolution). They are usually used in higher speed applications. I don't see them useful in the normal truck arena
 
This is quite the thread! A lot of good info in here. But on to the subject at hand...

In order to run two alternators on the same vehicle you need a controller like the one here: http://www.amplepower.com/wire/dual_alt/index.html

The reason for this is that with two alternators one will be working harder than the other. They will not share the load equally. This is because of small production variences in regulator set point of each alternator. The Ample Power website has a lot of good info on engine electrical. Go the the "Ample Power Primer" link on the main web site. Hope this helps.

Kevin
 
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Most over drive pulleys are designed for high RPMs and low drag (spin fewer times per crank revolution).

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Well, if "over"=above, and "under"=below, turning the alternator below stock speed would be under driving it, and turning it above stock speed would be over driving it.

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I don't see them useful in the normal truck arena

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If you have a 1-2 volt drop, in a useable Voltage range of 12-14 volts, and turning the alternator faster gets you 1-2 volts back at idle, ANYONE will notice the difference and applicability. Dim headlights/dashlights and slow heater motors are lame.
 
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First off, Bobby, your a dumb ass. You dont need two alternators. Everyone knows you can just bolt down a gas powered generater in back, this is called a SPLIT system. Just route your outgoing generator power directly to the battery cable,the negative one. This way it will make you go faster, and give you tons more horsepower,and remove the need to get and aftermarket mallory ingition. Just fill it up the same time you fill up your truck. And It will be really loud, (supposed to be that way),,,,,,just roll down the windows so the smoke dosent fill up the cab, and crank up the tunes. This is good to wire directly to your stero amp as well. Also, at christmas time ,,,you can run a bunch of cristmas lights on your truck (the flashing ones) to be more decrotive. You can also mount Santa on top of your truck to match. I hope this helps. /forums/images/graemlins/screwy.gif

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And while you're at it, get the gas powered leaf blower out of the tool shed and attach it under the hood somewhere in the engine bay with bailing wire and duct tape.
Some 3" PVC will work to connect it to your engine air intake plumbing.. Fill that sucker up when you fill up your truck and the generator in the back..
When someone pulls up next to you at a stoplight and wants to race, say hold on, get out pop the hood, and start up your leaf blower...
Wooollaa... Instant 20 lbs of boost. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/woot.gif /forums/images/graemlins/whistling.gif
/forums/images/graemlins/rotfl.gif
 
[ QUOTE ]
[ QUOTE ]
First off, Bobby, your a dumb ass. You dont need two alternators. Everyone knows you can just bolt down a gas powered generater in back, this is called a SPLIT system. Just route your outgoing generator power directly to the battery cable,the negative one. This way it will make you go faster, and give you tons more horsepower,and remove the need to get and aftermarket mallory ingition. Just fill it up the same time you fill up your truck. And It will be really loud, (supposed to be that way),,,,,,just roll down the windows so the smoke dosent fill up the cab, and crank up the tunes. This is good to wire directly to your stero amp as well. Also, at christmas time ,,,you can run a bunch of cristmas lights on your truck (the flashing ones) to be more decrotive. You can also mount Santa on top of your truck to match. I hope this helps. /forums/images/graemlins/screwy.gif

[/ QUOTE ]
And while you're at it, get the gas powered leaf blower out of the tool shed and attach it under the hood somewhere in the engine bay with bailing wire and duct tape.
Some 3" PVC will work to connect it to your engine air intake plumbing.. Fill that sucker up when you fill up your truck and the generator in the back..
When someone pulls up next to you at a stoplight and wants to race, say hold on, get out pop the hood, and start up your leaf blower...
Wooollaa... Instant 20 lbs of boost. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/woot.gif /forums/images/graemlins/whistling.gif
/forums/images/graemlins/rotfl.gif

[/ QUOTE ] Ahhh, yes, the good ol custom leaf blower cold air intake system.This will need to be adjusted though, at higher altitudes.To prevent any leaning of the motor.(been told that)........If you want to run two alternators, bobby, you have alot to learn baby bird. I agree with Ryan on this one, if your going this route, its important to run the Tripple Nipple Launcher style intake system (as described above) Hope this helps /forums/images/graemlins/thumb.gif
 
Thank you for the link. /forums/images/graemlins/eek.gif /forums/images/graemlins/thumb.gif
 
I believe the overdrive pulley term is from the speed of the motor. It doesn't make much sense to me either. The use of them is for normal operation during high engine speeds. I don't see it useful in trucks cause they don't go past 4000RPM's very often. The little rice guys, and hotrodders, hit 6000RMP often enough to notice a difference. If you have dim headlights at freeway speeds there are bigger issues than the pulleys. You use a smaller pulley so you won't have dim headlights at/around idle. That is my understanding for it. I may verywell have the underdrive term confused however.
 
Yeah, I think if you check out the March pulley systems, the "racing" ones are called "underdrive" pulleys.

Not saying it's necessarily right, just that I think that is the industry standard. Might be like "*sub*frame" connectors. Not correct, but almost universally used.
 
under drive pulleys slow the accessorys down from stock
when enough people bitched that they couldn't run a thumper sound system they added a line that slowed everything but the alternator down. at one time they called them 'amp' pulleys

racers use a huge pulley, like moroso sells, to avoid overspeeding the generator
no idea if that idea is based on fact
 
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[ QUOTE ]
First off, Bobby, your a dumb ass. You dont need two alternators. Everyone knows you can just bolt down a gas powered generater in back, this is called a SPLIT system. Just route your outgoing generator power directly to the battery cable,the negative one. This way it will make you go faster, and give you tons more horsepower,and remove the need to get and aftermarket mallory ingition. Just fill it up the same time you fill up your truck. And It will be really loud, (supposed to be that way),,,,,,just roll down the windows so the smoke dosent fill up the cab, and crank up the tunes. This is good to wire directly to your stero amp as well. Also, at christmas time ,,,you can run a bunch of cristmas lights on your truck (the flashing ones) to be more decrotive. You can also mount Santa on top of your truck to match. I hope this helps. /forums/images/graemlins/screwy.gif

[/ QUOTE ]
And while you're at it, get the gas powered leaf blower out of the tool shed and attach it under the hood somewhere in the engine bay with bailing wire and duct tape.
Some 3" PVC will work to connect it to your engine air intake plumbing.. Fill that sucker up when you fill up your truck and the generator in the back..
When someone pulls up next to you at a stoplight and wants to race, say hold on, get out pop the hood, and start up your leaf blower...
Wooollaa... Instant 20 lbs of boost. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/woot.gif /forums/images/graemlins/whistling.gif
/forums/images/graemlins/rotfl.gif

[/ QUOTE ] Ahhh, yes, the good ol custom leaf blower cold air intake system.This will need to be adjusted though, at higher altitudes.To prevent any leaning of the motor.(been told that)........If you want to run two alternators, bobby, you have alot to learn baby bird. I agree with Ryan on this one, if your going this route, its important to run the Tripple Nipple Launcher style intake system (as described above) Hope this helps /forums/images/graemlins/thumb.gif

[/ QUOTE ]

Oh my God guys, I'm gonna piss my pants. /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif
 
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