Under Pullies

[dntnvme]

I was wondering has anyone changed their under pullies on their TV's :undecided I was talking to my cousin today about beefing up the TV, and he mentioned something about Bullet Aluminum Small Pullies are suppose to give you more horses :confused: .

[tehehodi]

Billet alluminum pullies? i assume they would give a few ponies, the point is the motor doesn't have to work has hard turning a bigger heavier wheel and less power is being used from teh motor to power your belts. less stress on your motor pretty much or something liek that....help, anyone explain this better?

[Trailblazin]

The less rotating mass weight, the more power output. A friend of mine wants me to order and underdrive pulley for his G35, costs around $160 and advertised gains says it will free up 10-15hp... I'm thinking 5whp on the trailvoy if this ever gets done.

[dntnvme]

I have a place called Team C, They are in the City of Lakewood Ca, I can get the set for around 2 bills. My cousin said he would help me install them for free :D . Question are they worth the money for our TV's :undecided. If they are then I will be modding my pullies real soon :yes: .

[tehehodi]

wouldn't putting these on allow your motor to rev quicker/redline a little faster?

i recall having a udp on my talon:rolleyes:

[OurZoo]

Did you say free up more power Jay? I'm listening...:D

[StvsDenaliXL]

I'm listening too, interested on what this can do to the Voy:undecided

[jay boy]

Does the crank pulley on the 4.2 unbolt from the front of the engine or is ti part of the balancer? Jay

[gmcman]

Depends on how much underdrive you get....In some cases you will get lower alternator output at idle so when you are stuck in traffic at night it can draw your battery, just something to look for.

[the roadie]

The less rotating mass weight, the more power output.Color me skeptical. Alternators are like generators - you can't connect one to an electrical motor and suddenly have a perpetual motion machine. They work by mechanically loading the belt by exerting drag through the pulley. At idle, if the alternator's not being spun fast enough to generate the required juice, your lights will dim as the voltage droops. But as soon as the RPM comes up enough to get the alternator into its proper operating region, whatever electrical load it has will directly result in mechanical load on the engine of the same amount. If everything was 100% efficient, 746 Watts of electrical energy equals a horsepower. So if you have 30 Amps worth of headlights, let's say - times 12V, that''s 360W, or about 1/2 horsepower. If you spin the alternator at 500, 1000, or 2000 RPM it doesn't matter. The alternator will do whatever it has to (by way of the voltage regulator) to obtain that 1/2 horsepower to run the lights. This is the steady-state analysis of power.

So what's left to justify the snake oil of undersized pulleys? The dynamic analysis. As you accelerate from idle to full RPM, you're spinning up (and during shifts, spinning down) the rotating part of the alternator mass. A 25% underpulley will need 25% less horsepower to do that. If somebody claims a 5, 10, or 20 horsepower gain from a pulley, they're implying that the normal alternator is requiring 20, 40, or 80 horsepower for short times to spin up/down under stock conditions. For an item that has only 3-4 pounds of rotating mass, that's not a reasonable claim. What about the rotating mass of the crankshaft, that weighs a lot more? The power steering pump. The idle pulley. The belt itself? The transmission parts. The cam chain? And so forth.

Anybody who puts on an underdrive pulley should really be prepared to show dyno numbers under very controlled conditions to convince me there's real benefit. I'm calling snake oil on this mod based on what I know of engineering.

[OurZoo]

Tanks for the input Roadie. I'd be waiting for more info before doing anything.

[dntnvme]

I have to get more info but my cousin builds race cars and classic trucks. I didn't get the full understanding but from what he states there is a plus. I'm really not mechanically smart, but I know from his work he does great jobs. In other words he know his sh@#t. But you know when someone tells you something you try going off telling someone the story but you do not remember all details. After doing some more research I will post info. I have seen guys with the SS's change there pullies, let's see what they say :undecided

[jay boy]

The way that underdrive crank pulleys make extra HP is by slowing down ALL of the belt driven componets. When added together the fan ,PS pump,A/C compressor, water pump idlerpulley and the alternator take a lot of power.......at high RPM! Putting on an underdrive pulley will easly gain 5-15 HP at 6000RPM. At 2000 the gains will porbably not be measureable. Roadie is right to say that the alt will take whatever horsepower is nessary to put out the amps required. The gains are made off all the sets of blades moving slower with less restance. Jay