underdrive pulleys

[andrw]

what do they do? why do you need them?

thanks.

 

[bhuff30]

they slow down the speed your accesories turn. You don't.
It helps save several horsepower from being wasted on turning stuff, but you don't need it. There are better ways to spend 70-100 dolllars. I could fill my N2o bottle 3 times on that.
It becomes more important when you start turning the engine faster. If you are still making power at 6K rpm, and plan on shifting at 7K, you would want underdrive pulleys because they help the most at high rpms, and prevent your alternator from being overspun (although I have never heard of this actually happening )

 

[andrw]

ahh okay. gracias

 

[351wcoupe]

I could notice a difference on my girlfriend's turboed mustang. Its funny its "faster" without them but makes more power with them. With no other mods I would make a run with the pullies and it would spun hard through first and half of second. Without them and making an identical run the car just hooked and took off. So yeah they probably do help but didn't help me any.

 

[bhuff30]

I could notice a difference on my girlfriend's turboed mustang. Its funny its "faster" without them but makes more power with them. With no other mods I would make a run with the pullies and it would spun hard through first and half of second. Without them and making an identical run the car just hooked and took off. So yeah they probably do help but didn't help me any.

Which pulleys did you use? Just a 4" crank pulley, or did you use an alternator pulley too?
I have been thinking about it for my NA which I rev fairly high when I need to get anywhere quickly.

 

[351wcoupe]

Which pulleys did you use? Just a 4" crank pulley, or did you use an alternator pulley too?
I have been thinking about it for my NA which I rev fairly high when I need to get anywhere quickly.

I have the racer walsh aluminum crank and steel alt pullies. lol the pullies are almost the same size and it uses the stock size belt as long as your tensioner is in good shape.

 

[93GreenLX]

Would I see ANY difference at all with UDP's??

 

[93GreenLX]

Would I see ANY difference at all with UDP's??

I do have A FULL exhaust from the header on back and a CAI if that matters.. so what 110hp WOOHOO

 

[Red_LX]

351wcoupe bought my old underdrivers (which, by the way, are both aluminum). I had them on my 2.3L Mustang for awhile, never noticed a real difference. Put them on my Turbo Coupe for a short time after I got it, didn't really notice a difference there either, so I decided to sell them because they don't spin the alternator fast enough at idle and your lights dim and all that. Since the TC has several electronic accessories I figured more current at idle was a good idea.

 

[kiddiccarus]

what amperage is yout alternator? I am looking for one for my project

 

[351wcoupe]

351wcoupe bought my old underdrivers (which, by the way, are both aluminum). I had them on my 2.3L Mustang for awhile, never noticed a real difference. Put them on my Turbo Coupe for a short time after I got it, didn't really notice a difference there either, so I decided to sell them because they don't spin the alternator fast enough at idle and your lights dim and all that. Since the TC has several electronic accessories I figured more current at idle was a good idea.

I never noticed that alt pully was aluminum, maybe because its black. The aluminum BBK alt pully was 1/2 the weight though. I beat that pesky little charging problem with a powermaster one wire 140 amp Alternator that works great.

 

[GTPhreak]

seems like a bunch of people around here say they cant feel much difference, but in the 5oh camp it adds ~10hp dyno proven

 

[bhuff30]

seems like a bunch of people around here say they cant feel much difference, but in the 5oh camp it adds ~10hp dyno proven

I know, and it is funny because we have the same alternator and nearly the same power steering pumps. The only difference is that the 5.0 probably has a bigger water pump, and it has that air pump hanging off the side.
seems like it 'should' make a big difference on our engines. I am really tempted to try them. Want to sell them 351w? I know I won't have any problems charging my battery with a 160A 3G alternator, and a 1000rpm idle (havn't figured out why )

 

[GTPhreak]

dang a 160A!?! I need one for the gt then put the 130 on 4banger hehehe..yeah im sure the water pump doesnt help much, but the air pump doesnt really have much effect (unless it siezes up like mine did last week)