Light Weight Smaller Overdrive Pulley Decreases HP?!?

[amdsoldier]

Damn can't seem to stop thinking about my car and get some sleep. Good thing too, I forgot to ask you guys this question.

I bought one of these here: http://cgi.ebay.com/ebaymotors/ws/eB...category=38656

It's quite a bit smaller than stock and I talked to a mechanic I know that hooks me up... Well he's telling me that this may slow down my car because it's smaller in size and thus I would see a decrease due to lower RPM's or something. He confused me and I don't know exactly what he's talking about.

He went on to say the car was designed for the stock size and that the AC, and everything else connected to it will be affected negatively.

Um can someone please explain this one to me?

Like what are the benefits exactly I guess and if there are really negatives going with a smaller aluminium overdrive pulley.

This sucker was expensive, ran me $75 bucks and now I need to spend probably that much in belts alone and when I heard that from him, it was like a nightmare. :agh:

[89Turbo944]

for every 1 pound of rotating mass=8pounds static weight. Every pound lost off the crank is equal to about 2.7whp gain.

The pulley is lighter so it will give you a bump in power. It is smaller which means it is easier to drive, which translates to being easier to drive all the other pulleys on your engine.

The accessories are driven slower, but you will not notice anything different unless you have alot of stero equipment or a very large draw on the electrical system.

Hope that helped a bit.

[LandoAWD]

UDP is one of the best power for the dollar mods on an N/T.

[ashah000]

How do these not fit on to your car?
Let me know.. because i was planning on buying these.

[LandoAWD]

As long as you don't have a turbo model 1998 Eclipse, it will fit.

[amdsoldier]

ashah000, what I meant by not fitting is they require new belts which i didn't have with me when I wanted to replace the UDP. These are the belts sizes you'll need: Alternator #K040320 / AC & Power Steering #K050490

89Turbo944, wow a 2.7whp increase for every pount shaved off? So it's it's a 8lb difference, I may see 21.6whp increase? I would of been happy with 5.

I wonder what kind of a hit is it to the electrial system though? I do have a $10,000 stereo setup in this car, but it's not high wattage, just sound quality.

I do have a yellow Optima battery, and I'm hoping it's powerful enough that I won't notice any difference.

But to be on the safe side, I'll kinda list what I have quickly and you guys can maybe tell me if I should be concerned about having less power for electrial.

Eclipse 8053 deck
8", 5.5", tweeker 3-way MBQuart speaker setup
Phoenix Gold SX6600 amp - modded for more power by Phoenix Gold engineers
6X 10" JL subs
capactor

and in a nutshell that's pretty much it. Appreciate the help!

[kjewer1]

The numbers quoted (2.7 whp etc) were either specific to a particular setup, pulled out of someones ass, or a wannabe engineer's wet dream. There is no way to can estimate it down to one decimal place. And it will vary with each car. It will more likely be expressed as a percentage than a hp per pound figure. Also, the amount of gain will vary with not only the weight reduction but the weight reduction relative to its moment of inertia, or distance from the center of the shafts rotation.

You certainly will not see a 21 HP increase at the wheels.

[amdsoldier]

Originally Posted by 95 GSXracer

The numbers quoted (2.7 whp etc) were either specific to a particular setup, pulled out of someones ass, or a wannabe engineer's wet dream. There is no way to can estimate it down to one decimal place. And it will vary with each car. It will more likely be expressed as a percentage than a hp per pound figure. Also, the amount of gain will vary with not only the weight reduction but the weight reduction relative to its moment of inertia, or distance from the center of the shafts rotation.

You certainly will not see a 21 HP increase at the wheels.

Hehe yeah I figured it wouldn't be anywhere close to that. But um I'm worried about the electrial power decrease - I guess thats what you'd call it. Because my car right now is having some alternator noise and I had to decrease the gains on the amp to quiet it down. I was thinking the alternator could be stressed too much already. Or I was told from Cartoys that it could be a interference from something else (there used to be a little more equipment, tons of wires everywhere). So I dunno just wondering what your thoughts would be on it.

[Spectrum]

Underdrive pulleys are just stupid to add, enough said. The stock pulley is so big because it absorbs vibrations. So if you want your crank to crack, get one.

[kjewer1]

In that case I would say the few HP you are going to free up are not worth the trouble. DSM alternators arent huge to start with (65 amp I believe), and it seems your stereo is an important part of your car. I wouldnt risk it. On a brighet note though there is a larger alternator that physically bolts right in, be needs some wiring (different connectors I believe) from certain galants, 95 amps if I'm not mistaken. Thats a nice increase, and any good stereo shop should be able to wire it in. Might be worth looking into, especially if your alternator shits the bed... Either way, good luck with it.

[amdsoldier]

Originally Posted by Spectrum

Underdrive pulleys are just stupid to add, enough said. The stock pulley is so big because it absorbs vibrations. So if you want your crank to crack, get one.

Yeah the mechanic said something around these lines...

[amdsoldier]

Originally Posted by 95 GSXracer

In that case I would say the few HP you are going to free up are not worth the trouble. DSM alternators arent huge to start with (65 amp I believe), and it seems your stereo is an important part of your car. I wouldnt risk it. On a brighet note though there is a larger alternator that physically bolts right in, be needs some wiring (different connectors I believe) from certain galants, 95 amps if I'm not mistaken. Thats a nice increase, and any good stereo shop should be able to wire it in. Might be worth looking into, especially if your alternator shits the bed... Either way, good luck with it.

Hmm interesting that larger alternator sounds like something I may just need.

Would you happen to know where I may beable to pick one up? Checked ebay and dsmtuners and didn't notice anything.

Thanks!

[kjewer1]

The stock pulley absorbs harmonic vibrations because it includes a harmonic damper (the rubber section in the center). Not having one can contribute to crankwalk (as documented by a respected BMW tuner), but since this was an NT I didnt want to go into it. Just another reason to sell that on ebay, the same way you found it

[amdsoldier]

Originally Posted by 95 GSXracer

The stock pulley absorbs harmonic vibrations because it includes a harmonic damper (the rubber section in the center). Not having one can contribute to crankwalk (as documented by a respected BMW tuner), but since this was an NT I didnt want to go into it. Just another reason to sell that on ebay, the same way you found it

I see thanks for explaining that a bit.

Without adding a turbo kit or a nos bottle, I really dunno how to add more power. I just want a little bit more punch.

Maybe you or someone else can suggest also quickly what other things I may buy to speed up the car but not affect the engine or stereo negatively.

mods I have so far:

4-1 headers
2.5" catback
NGK Iridium IX spark plugs
larger spark plug wires
AEM V2 CAI

And I believe cam gears are not recommend that much due to their wear on the engine components...?

Would you say getting light weight wheel (~15lb) would help me out here in the speed department?

Also planning on buying a short shifter, maybe that will help a bit too.

[89Turbo944]

Originally Posted by 95 GSXracer

The numbers quoted (2.7 whp etc) were either specific to a particular setup, pulled out of someones ass, or a wannabe engineer's wet dream. There is no way to can estimate it down to one decimal place. And it will vary with each car. It will more likely be expressed as a percentage than a hp per pound figure. Also, the amount of gain will vary with not only the weight reduction but the weight reduction relative to its moment of inertia, or distance from the center of the shafts rotation.

You certainly will not see a 21 HP increase at the wheels.

Time to eat your words.

Modifier Mag, Issue 4/30, April 2003. Page 61 Paragraph 3.
and i quote "Every pound lost off the cranksahft averages out to be 2.7whp gain."

This was tested on a 2G Eagle Talon. All the results were from dyno testing. All be it, they used the Unorthadox Racing Underdrive pulley Ultra SS kit. Which includes all accessorie pulleys. But the quote still applys.

On my 300ZX i picked up 23whp, and the kit claims to give 25whp. So i think it is fairly accurate.