Underdrive pulleys.

gmctrucks · 10-15-2008, 07:03 PM

OK guys what would happen if I were only to use the harmonic power pulley and not use the alternator pulley like I have now? I'm thinking it won't charge correct right meaning it will under charge someone correct me please.
GMC

93blazer · 10-15-2008, 08:06 PM

im not sure about that one man , i mean it has a charging range but they charge the same no mater what your rpm is so i guess i would try it and hope it doesnt burn up the alternator

JOHN JAY · 10-15-2008, 08:43 PM

The alternater puts out voltage in relationship to the rpm's the regulator determines the charge voltage without the regulator and adjusting the speed you can run any portable 120v power tools welder, drill ect... So to answer your question your aftermarket pulley puts less drag on the motor increasing mpg

75K30 · 10-15-2008, 10:09 PM

You will only gain half of the performance that the entire pulley kit was designed for.
The intent is to slow down the belt driven components and reduce parasitic losses.
The pulleys provided maximize this, and keeping the alternator spinning a little bit faster than the kit was designed to do would reduce it affects.
Because the alternator is still turning within its low end limits, and high end range, it will still charge just fine.
Pulleys and power are really splitting hairs. You could obtain better horsepower results by removing the spare tire from the vehicle. Really, if you are looking for performance, or even better mileage (or both), put the vehicle on a diet.
Loose the tools, loose all of the non essentials, and you will find gains that far outeigh those found in a set of pulleys.

gmctrucks · 10-15-2008, 11:10 PM

Well when I placed pulleys on my truck I test drove it before with my dad because he thinking it's not going to make that much difference well after I placed them on we test drove it again on the same spot and it made my truck get up and go just look at all the guys/gals running at the tracks the all have power pulleys or should I say most of them and the reason I was asking because I bought just this pulley for the harmonic pulley and I was wondering how it affect an engine without having the one for the alternator now this pulley has for both types of belts V-belts and a Serpentine belt it was from some guy on Ebay that was unloading it cheap I wanted my buddy to try it on his truck but we haven't done it yet. My dad said wow it did make it get after it better I guess it would be like a ten speed bike-cycle. And I do agree the less weight the better that means I need to get on a big times diet. LOL

75K30 · 10-15-2008, 11:43 PM

The crank pulley alone will have the greatest affect because it slows down everything, from the water pump to the power steering pump.
Try to install a switch on the alternator, and open the field.
This will render the alternator useless, and it will have only the drag from the bearings, and not fromt the generator.
You will gain a ton form this. Alternators drag a bunch depending on load, and if you prevent it from charging for the time you are making a pass, you will find large benifits. Turn the alternator back on when you drive normally and you are in big time.
alright it is not that big of a deal, but better than the alternator pulley.

10-15-2008, 07:03 PM	#1
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,635	Underdrive pulleys. OK guys what would happen if I were only to use the harmonic power pulley and not use the alternator pulley like I have now? I'm thinking it won't charge correct right meaning it will under charge someone correct me please. GMC

10-15-2008, 08:06 PM	#2
93blazer Senior Member Join Date: Oct 2008 Location: south BAMA Posts: 284	im not sure about that one man , i mean it has a charging range but they charge the same no mater what your rpm is so i guess i would try it and hope it doesnt burn up the alternator __________________ IF YOU AIN'T FIRST YOUR LAST SHAKE AND BAKE !!!!!!!!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Underdrive pulley????	BLK1500	Chevy Truck Forum	8	06-15-2008 12:55 PM

10-15-2008, 08:43 PM	#3
JOHN JAY Senior Member Join Date: Sep 2008 Posts: 196	The alternater puts out voltage in relationship to the rpm's the regulator determines the charge voltage without the regulator and adjusting the speed you can run any portable 120v power tools welder, drill ect... So to answer your question your aftermarket pulley puts less drag on the motor increasing mpg

10-15-2008, 10:09 PM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 3,299	You will only gain half of the performance that the entire pulley kit was designed for. The intent is to slow down the belt driven components and reduce parasitic losses. The pulleys provided maximize this, and keeping the alternator spinning a little bit faster than the kit was designed to do would reduce it affects. Because the alternator is still turning within its low end limits, and high end range, it will still charge just fine. Pulleys and power are really splitting hairs. You could obtain better horsepower results by removing the spare tire from the vehicle. Really, if you are looking for performance, or even better mileage (or both), put the vehicle on a diet. Loose the tools, loose all of the non essentials, and you will find gains that far outeigh those found in a set of pulleys.

10-15-2008, 11:10 PM	#5
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,635	Well when I placed pulleys on my truck I test drove it before with my dad because he thinking it's not going to make that much difference well after I placed them on we test drove it again on the same spot and it made my truck get up and go just look at all the guys/gals running at the tracks the all have power pulleys or should I say most of them and the reason I was asking because I bought just this pulley for the harmonic pulley and I was wondering how it affect an engine without having the one for the alternator now this pulley has for both types of belts V-belts and a Serpentine belt it was from some guy on Ebay that was unloading it cheap I wanted my buddy to try it on his truck but we haven't done it yet. My dad said wow it did make it get after it better I guess it would be like a ten speed bike-cycle. And I do agree the less weight the better that means I need to get on a big times diet. LOL

10-15-2008, 11:43 PM	#6
75K30 Senior Member Join Date: Jul 2006 Posts: 3,299	The crank pulley alone will have the greatest affect because it slows down everything, from the water pump to the power steering pump. Try to install a switch on the alternator, and open the field. This will render the alternator useless, and it will have only the drag from the bearings, and not fromt the generator. You will gain a ton form this. Alternators drag a bunch depending on load, and if you prevent it from charging for the time you are making a pass, you will find large benifits. Turn the alternator back on when you drive normally and you are in big time. alright it is not that big of a deal, but better than the alternator pulley.