Question can i have both the alternator and crankshaft underdrive pulleys?

[heavy49]

to my knowlege tha crankshaft udp will decrase the force needed to move the other parts and the alternator udp will increase the turns of the alternator so one will comeansate the other speaking of alternator power. rigth?

[dareall]

instead of asking here, you might get better answers from manufacturers of these parts. Automotive magazines would be another good source for this information as well. Here is an example of information from one such site

Top 5 Questions About Underdrive Pulleys

1. "Do underdrive pulleys really deliver more horse power?"
Every experience we have with underdriving engine accessories shows that yes underdrive pulleys do deliver more horse power by freeing up power lost to parasitic drag. The amount you will realize depends on your car and the accessories you are driving, a car with alternator, water pump, power steering, A/C and a smog pump will see a larger HP gain then a car with alternator and water pump only. Dollar for dollar underdrive pulleys are one of the best value for HP gain on the market. But don't take our word alone on this, every magazine we have seen who have tested under drive pulleys has show a HP gain, some as high as 12.5 HP. Click here to see how 5.0 Mustang & Super Ford "Bolted-on" an easy 15HP for less than $100! and all in under one hour.



2. "But won't underdrive pulleys cause a charging problem?"
Again that depends on your car and how and when you drive. Automotive manufacturers build a certain amount of extra capacity into their cars for situation of high demand like driving on a cold rainy night with the lights on plus whippers and defrosters going. An older car with a less then optimum charging system and a small weak battery may have charging problems with underdrive pulleys and some cars with monster audio installations require higher that normal electrical demands. A well maintained auto should have no problem at all. Sometimes raising the idle by 100 RPM is all it takes to bring the charging rate back up to normal.

If electrical charging is an issue with your particular application March Performance has a smaller alternator pulley available to increase alternator output but to still allow a HP gain from underdriving the other accessories.



3. "Won't underdrive pulleys cause a engine cooling problem?"
Again that depends on your car and how and when you drive. Putting underdrive pulleys on cars with already minimal cooling capacity could conceivably push the car into overheating but our experience is that 99.9% of the cars out there has enough reserve cooling capacity to use our pulleys. Some user find that the simple installation of a cooler thermostat is all it takes to bring the temperature back into normal range. Underdive Pulleys can in some cases cure cooling problems. With racing applications cavitation can be a problem at high rpms. When a pump cavitates, it actually spins too fast to push coolant, Coolant must also stay in the radiator long enough to lose heat before returning to the motor so you can actually move coolant too fast. Both these issues can be solved by using underdrive pulleys.

But If low speed cruising is your thing then March Performance line of High Water Flow Ratios pulleys may be just what you need to prevent overheating in those situations.



4."Underdrive pulleys sound good but won't an electric water pump set-up give me even more HP?"
Yes it is conceivable an electric water pump can give you more HP than a underdrive pulleys set BUT there are some issues you should consider before you make that commitment. Your HP gain with an electric pump may not be as much as you think, in a recent test Hot Rod Magazine ran our performance ratios pulleys on a small block Chevy (alternator, water pump only) and to their surprise our pulleys only made 1 HP less then a electric water pump set-up. You should also consider that electric kits flow even less water then a underdrive pulley kit and that could cause cooling problems. Most electric WP are made for racing applications and not designed to be run for long periods of time, and if that electric motor gives out you are stuck with no water flow at all unlike a standard water pump which may start to leak and make noise but can allow you to limp home. The electric pump does draw power from your charging system and so you can't underdrive your alternator, you must have adequate electrical power just to drive the water pump.



5."How hard are they to install?"
Unlike engine modifications like cams, cylinder heads and intake and exhaust, underdrive pulleys can be the simplest power freeing modification you can do to your car. Some special tools are required such as an impact wrench to zip off the alternator pulley and a crankshaft dampener puller if your installation requires removal of the crank pulley/dampner assembly but all and all most kits are a simple "Bolted-on" operation. Our Mustang 5.0 pulleys can be installed without even draining the cooling system, Click here to see how to "Bolted-on" in less than an hour. Even if you are not the do it yourself type any automotive shop should be able to install your pulleys at a reasonable price.

March Performance

http://www.marchperf.com/tiptricks/underdrive2.html

this should help you get a better idea rather than hear what someone "thinks" it is supposed to do

[DOUGIESTYLE]

I have an overdrive pulley on my alternator. It compensates for the underdrive pulley on the crank. I dunno if it's the reason my lights don't dim when I'm idling or if there's a special lightning bug living in my headlights.

[dareall]

the esslinger and ford racing pulleys I use don't really have the problem (at least it is not noticeable) without an overdrive pulley on the alternator. When I drive around in the car with the powder pulley it is noticeable at every stop at night.

[powder]

If your crank UDP is 20% under size, it under drives your accessories 20%. If you then put a 20% under-drive alt pulley on, it adds another 20% from that point, which isn't necessarily 40% but it's close to it, and at idle you won't get the performance you need from the alt. You can get a chip to bump your idle up but why even bother with the alt pulley for absolutely no benefit.

The Powder crank UDP is 40% under-drive. This is why i designed and made a Powder Alt ODP, to compensate for some of the loss at idle, but it doesn't do much at higher rpms to be honest because once you hit about 1500 rpms, even with the stock alt pulley, you gain your voltage back. It is 30% over-drive, which is about as good as it can be given the size of the original alternator pulley. That said, a Ford Racing crank UDP (20%) and a Powder alt ODP is overkill, since you're only under-driving 20%, but it may help if you have a big stereo. A side note being, increased wear on your alternator since it will be spinning faster at idle by 10%.

[swedevil]

If your crank UDP is 20% under size, it under drives your accessories 20%. If you then put a 20% under-drive alt pulley on, it adds another 20% from that point, which isn't necessarily 40% but it's close to it, and at idle you won't get the performance you need from the alt. You can get a chip to bump your idle up but why even bother with the alt pulley for absolutely no benefit.

The Powder crank UDP is 40% under-drive. This is why i designed and made a Powder Alt ODP, to compensate for some of the loss at idle, but it doesn't do much at higher rpms to be honest because once you hit about 1500 rpms, even with the stock alt pulley, you gain your voltage back. It is 30% over-drive, which is about as good as it can be given the size of the original alternator pulley. That said, a Ford Racing crank UDP (20%) and a Powder alt ODP is overkill, since you're only under-driving 20%, but it may help if you have a big stereo. A side note being, increased wear on your alternator since it will be spinning faster at idle by 10%.

I honestly didn't know all that...

[iceracer]

UDP- slows it down. ODP- speeds it up.

[mechtech]

Swede -
Well, what did you think "underdrive" meant??

[heavy49]

hey Dougiestyle whats the size of the serpentine u r running? i going to install both pulleys

[swedevil]

Swede -
Well, what did you think "underdrive" meant??

I knew the basics of it and what they did. I just didn't know all the details. He went in to detail with explaining the percentages and all

[Mimino]

If your crank UDP is 20% under size, it under drives your accessories 20%. If you then put a 20% under-drive alt pulley on, it adds another 20% from that point, which isn't necessarily 40% but it's close to it, and at idle you won't get the performance you need from the alt. You can get a chip to bump your idle up but why even bother with the alt pulley for absolutely no benefit.

The Powder crank UDP is 40% under-drive. This is why i designed and made a Powder Alt ODP, to compensate for some of the loss at idle, but it doesn't do much at higher rpms to be honest because once you hit about 1500 rpms, even with the stock alt pulley, you gain your voltage back. It is 30% over-drive, which is about as good as it can be given the size of the original alternator pulley. That said, a Ford Racing crank UDP (20%) and a Powder alt ODP is overkill, since you're only under-driving 20%, but it may help if you have a big stereo. A side note being, increased wear on your alternator since it will be spinning faster at idle by 10%.

would running your odp negate any of your udp's benefits?

[iceracer]

I've wondered that myself. But then the water pump,ps ans AC all run slower and the crank pulley being lighter offsets some. So you may lose a little but not a significant amount.

[madmatt2024]

would running your odp negate any of your udp's benefits?

It probably takes away some of the benefit but not a lot. The alternator is one of the easiest accessories to spin to begin with so spinning it faster isn't going to increase the required force by that much.

[Mimino]

thanks, guys. i might keep the odp as a trophy then

[powder]

It probably takes away some of the benefit but not a lot. The alternator is one of the easiest accessories to spin to begin with so spinning it faster isn't going to increase the required force by that much.

Where did you read this? Alternators have current that causes friction. It is not the easiest to spin.

Water pumps have friction in the beginning but as it gets the fluid moving it flows easier.

An alternator? More friction the faster it goes.