if you have a supercharger (3.125 pulley), would it be ok to get a udp or no?

 

why would you want that? WOuldnt you just be underdriving your S/C as well... so that means the rotors will spin slower, thus giving you less boost?

edit:: I take that back... I dont knwo what would ahppen, because you are not underdriving the S/C directly... hmm, lets hear from the other people.

 

YOu would underdrive the SC. The crank pulley would be underdriven and so would the alternator pulley which does drive the SC pulley. So boost would be down.

 

Not a good idea. You'd be losing a ton of HP by using an underdrive pulley. The amount of boost you put out is dependent upon who fast your SC spins. The faster it spins the more boost you make. Using a UDP will make it spin slower, make your car slower, and make you look stupid because you are wasting a ton of power. Probably shouldn't do it.

 

But you have to remember that not all UDP's are smaller diameter. Some are just significantly lighter in weight.

 

Then they shouldnt be called UDPs right? They should be called Lightweight Pullys... because they aren't really underdriving.. no?

 

UR makes a lightweight supercharger pulley for the maxima. Try going to their website.

 

No, because underdriving can be acheived in two manners. One is by reducing the diameter of the pulley, and the other is by reducing the mass of the pulley (regardless of whether or not the diameter is reduced).

 

alright guys, thank you very much for all the info. i guess i wont be getting the udp. glad i asked before i bought the thing. thanks again

 

:attention

Go to http://www.unorthodoxracing.com/ or call them and ask them for the lightweight supercharger pulley for a maxima.

 

This is the pulley you seek, buy it and enjoy

http://www.sportcompactwarehouse.com/PROD/121001002

 

So its still an overdrive pulley? I dont see how you underdrive it if you just make it lighter... I thought underdriving had to do with gear ratios, and in this case, you dont change the ratio because the diameter of the pulley remains the same... just the weight changes... hmm?

 

The link I posted to the ligher pulley is probably the same crap as an OEM one except its a lighter version. The regular UDP is much smaller/lighter in diameter then a OEM diameter crank pulley. Dont know if any of you own one or installed one? The link I posted is the crank pulley to replace if you own a SCer.

 

You're making this much too complex. Think of it this way...

Lighter wheels are better than the stock heavy wheels, right? Why is that? Because it takes less force exerted on the lighter object in order to spin it to XXX RPM levels as the stock wheel. Same principal applies to the crank pulley. If it's lighter, but the same diameter, it will take less force to spin to XXXX RPM compared to the stock pulley.

 

Right right... I understand that.... but what I don't understand is... why would you be underdriving if your gear ratio remains the same. I understand that you would require less force to rotate that object... I think the weight is the biggest thing, because even if you have a "smaller" pulley, and it was heavier than the stock one, the rest of the accessories that are on the same belt will spin SLOWER... I think it is implied that since the UDP is smaller in diameter, its "lighter", so people that get UDPs automatically assume that they are getting more HP because the UDP is smaller, and not that its lighter..... Am i correct on these assumptions? Or am i bsing?


edit:: if this is the crank pulley, then the stuff will spin slower (because thats the pulley thats actually spinning the belt)... when its smaller in diameter or heavier. But the above would apply to any other accessory pullies, right?

 

OK...85% of the power on the UDP come from wieght reduction and 15% comes from the smaller diameter. So on the SC cars if you lighten the pulley weight and not the diameter, then you have under driven the pulley via wieght not gear ratio or diameter.

 

Regardless of how much power gain is due to lower weight and how much is due to underdriving the accessories, they are called underdrive pullies because they underdrive the accessories. Making them out of aluminum for weight reduction is a bonus.

So what you want is an aluminum crank pulley with the same diameter as stock. I would think your money would be better spent somewhere else, but whatever floats your boat . . .

 

Wait wait... but if the crank pulley stays the SAME diameter, but just WEIGHS less, wouldnt the gear ratios stay the same, BUT the crank will be able to spin faster (less parasitic losses)? And in doing so, the belt thats attached to the crank pully would move faster, making the accessory pullies spin faster too. So its not really "underdriving" anymore, is it?

 

It will spin UP faster, but not faster. The RPM's of the crank will still be the same. Your idle will not be higher and niether will your read line. But you will get there much faster.
The acc stay the same as factory. You just gain power due to the reduction of wieght and you get to redline quicker.

 

So you're saying that 6000 rpm with a lightweight pulley is faster than 6000 rpm with the stock pulley?

Okay, forgive me, I know you meant you will get to 6000 rpm (for example) sooner with a light weight pulley than with a stock pulley. Yes, that is true.

 

right.. pardon the miscommunication.. i gotcha... I just dont understand why it would be underdriving if the accessories pullys are spinning at same rate as before the lightened pully. albeit it would be easier to spin them faster...

 

the udp just will not work as good as stock, that s the way it is

 

just think, once you get something spinning, if its heavier it will spin faster, or with more force(harder to stop or slow down). your crank is where the power comes from and you wouldnt want to lesson your power. simple

 

Ummm, no, that's inertia you're thinking of...and you make more power to the wheels by reducing engine friction (thus using Synthetic oils, lighter crank pulley, lighter flywheel...).