Underdrive Pulley Myth?

[tripplediamonds23]

I know i heard once a while ago that if you have audio components such as an amp and a sub the underdrive pulley doesn't work the right way or robs power from the electrical audio source or something like that.

Today my friend told me otherwise and explained it a little to me and it made sense, i just wanted to see what you guys had to say about this. If i have a sub and amp is it going to be affected by the pulley, or would it work completely fine?

thanks in advance.

[akley88]

if you under drive a lot you can have some issues with power, but i have the lightened crank pulley and dont get any power loss issues

[snakeeyes]

only thing ive notice with mine is,if i have the fan switch on high,it will slow a little at a stop but the ac is colder.i'm running a 1000 watts rms with no issues.

[Daxenth]

i have the pulley. your gonna notice your power change a bit. BUT thats also because once you mod your RPM will drop to about 550/600 at idle. thus not spinning your alternator and giving you less of a flow. ive had my pulley on since july last year. im running 2 12" subs at deafening volume, all new speakers that draw more power, halos, and LEDs underbody/ interior. havent had to swap my battery or alternator.. in other words i just prolly worried you just to tell you your fine. Yes your idle will drop slightly, but your not "robbing power" just making a bit less at idle.. know what i mean? the instant i hit the gas my lights are bright and LEDs light up and its all good just do it man!

[Kreel]

It's all based on how many amps are being drawn by all your electrical components. It will be most noticeable at idle as the alternator pulley is now at its slowest. So when you drop from a stock size pulley to an underdrive pulley it will go even slower. Let's say you have 2 pulleys both 2" wide. 1 revolution from pulley A = 1 revolution from pulley B. Now drop pulley A to 1" wide. It will take 2 revolutions from pulley A to = 1 revolution from pulley B.

[tripplediamonds23]

yeah i got you daxenth, definitely adding it to the mod list.

[trevroar]

Do your alternator and the rest of your electrical system a favor and get a deep cycling battery or at least a stereo capacitor- especially if you're running stereo equipment. There's much more going on when things start dimming, and fans slow down. The strain goes through everything on your car. You have the think about the things you can't see such as your fuel pump and coil packs. These things need a solid 12v to function correctly. They speed up and slow down just like your heater fans when there's a draw on your electrical system. So if you think you'are not damaging anything, think again.. You can get an entry level Yellow top Optima battery to run your accessories for under $160-ish at Autozone

[ALBOE]

Originally Posted by trevroar

Do your alternator and the rest of your electrical system a favor and get a deep cycling battery or at least a stereo capacitor- especially if you're running stereo equipment. There's much more going on when things start dimming, and fans slow down. The strain goes through everything on your car. You have the think about the things you can't see such as your fuel pump and coil packs. These things need a solid 12v to function correctly. They speed up and slow down just like your heater fans when there's a draw on your electrical system. So if you think you'are not damaging anything, think again.. You can get an entry level Yellow top Optima battery to run your accessories for under $160-ish at Autozone

x2

[snakeeyes]

Originally Posted by trevroar

Do your alternator and the rest of your electrical system a favor and get a deep cycling battery

looks like a batt will be next on my list then.

[Daxenth]

Originally Posted by trevroar

Do your alternator and the rest of your electrical system a favor and get a deep cycling battery or at least a stereo capacitor- especially if you're running stereo equipment. There's much more going on when things start dimming, and fans slow down. The strain goes through everything on your car. You have the think about the things you can't see such as your fuel pump and coil packs. These things need a solid 12v to function correctly. They speed up and slow down just like your heater fans when there's a draw on your electrical system. So if you think you'are not damaging anything, think again.. You can get an entry level Yellow top Optima battery to run your accessories for under $160-ish at Autozone

ive read and researched and figured out that stereo capacitors do next to nothing. they help but. not the way people think. although i do agree with you. i NEVER thought about any of the shit you cant see dim. but im glad i do my best to keep it from happening. i drop to neutral at lights and tap the gas. may not be good for the car but it keeps everything at a relative norm. ive read alot of people swapping to Redtops. im not sure if a simple battery swap would be all i need. but if it is then im sold. cause im not going through the hassle of running 2 batteries. just a PITA

[trevroar]

Red tops are just starting batteries they do nothing for accessories. Yellow top have reserve cells built in that are intended for extra draw. So don't waste your money on red tops or blue tops.

[Daxenth]

but yellow... ewwwwww.... lmao i think im gonna with my paycheck after next... gotta limit it to one mod a check. and next is my gauges.

[trevroar]

stay away from glowshift junk, mine didn't even make it a year

[Daxenth]

its all i got. i dont want off brand stuff and thats the first bad thing ive heard about it lol

[trevroar]

I got the digital gauges, and some of the LEDs are dead so its just looks dumb. However, they still do work sorta. If you got analog you'll prolly be better off.

[Daxenth]

only digital one im getting is the nitrous pressure. i have an AEM wideband and the other glowshift would be the analog Fuel pressure.. so

[3CL1PS3]

i have an optima yellow top, one 12" sub, and halo projectors. my alternator has slowly been taking a crap ever since installing the pulley. i put a voltage gauge in and when i turn the stereo up my volts will drop to 10 or lower and stall if im at a standstill. i even put the stock one back one to test and it was fine. sometimes its worse than other times like it doesnt always stall but also if i turn the car off it hasnt been left with enough juice to arm antitheft or let the window go up when the door is shut

[Daxenth]

so your battery didnt help?

[trevroar]

must be the combination of a failing alternator and uP. If you got an extra $250, you can buy the high output 220v alternator over the OEM 110v alternator. Alternators are cheap on eBay, got mine for $45 delivered.

Also, your Optima isn't going to take a charge unless its getting closer to 13.5 - 14 volts from the alternator

[Daxenth]

Originally Posted by trevroar

must be the combination of a failing alternator and uP. If you got an extra $250, you can buy the high output 220v alternator over the OEM 110v alternator. Alternators are cheap on eBay, got mine for $45 delivered.

Also, your Optima isn't going to take a charge unless its getting closer to 13.5 - 14 volts from the alternator

how do you know what your alternator is feeding out?

you know.. why wouldnt they make the power split off like you said? like.. the battery gives a constant 12v and all the accessories run off the alternators power?

[trevroar]

With the car running, use your volt meter on the battery, it should always be above 13v no matter what's turned on, radio, lights, AC, etc. Mine is usually around 14v. This is because the alternator is charging the battery.

When the car off, then you are getting the volts of the battery only, it never should be lower than 12.4 volts when nothing is running

[3CL1PS3]

Yeah that's where the problem is. Driving its at a constant 14-14.5v but idle is anywhere from 10-12 so as soon as windows are rolled a/c turned on or radio turned up, the volts drop and I either stall or the navi stereo will restart. Ya I just found out Mitsubishi wasn't going to cover my alternator so ill hopefully get lucky on eBay. What brand did you get trevroar?

[trevroar]

I just got the OEM 110v but the one I bought was for my GT swap

[redstar666]

Originally Posted by trevroar

Red tops are just starting batteries they do nothing for accessories. Yellow top have reserve cells built in that are intended for extra draw. So don't waste your money on red tops or blue tops.

awsome man thanx for the batt tips

[tripplediamonds23]

trevor, electrically im only gonna have the stock rf sound system, radar dector, interior leds, and an ipod cable running along with simple common performance mods. would the yellow top be necessary, ill probably still do it at some point because its a really good idea and a beneficial thing to do, but would it be necessary to do right away?

[trevroar]

You should be fine with the stock battery with no worries

[Cedric]

Your fine Dont think to much off it

[Isamu]

holy crap, someone needs to redesign your underdrive pullies, or you need to go with an over drive pully...

the pully should just be lighter.. not smaller...

[Cedric]

Originally Posted by Isamu

holy crap, someone needs to redesign your underdrive pullies, or you need to go with an over drive pully...

the pully should just be lighter.. not smaller...

Its not much smaller and its definitely at least half the weight of the original which is pretty heavy

[Isamu]

Originally Posted by Cedric

Its not much smaller and its definitely at least half the weight of the original which is pretty heavy

the underdrive pully really shouldn't effect your power.. its just less weight for the engine to move..

[trevroar]

Originally Posted by Isamu

holy crap, someone needs to redesign your underdrive pullies, or you need to go with an over drive pully...

the pully should just be lighter.. not smaller...

lol, the characteristics of an under pulley is to be smaller, hence the name. Light weight pulleys are just has you said, lighter. RRE's pulley is what it says it is, a light weight under drive pulley.

[Daxenth]

Originally Posted by Cedric

Its not much smaller and its definitely at least half the weight of the original which is pretty heavy

mhmm. Stock is a little over 3 lbs

RRE= like 1.2 lbs i think. its very noticeable.

[snakeeyes]

Originally Posted by Daxenth

mhmm. Stock is a little over 3 lbs

RRE= like 1.2 lbs i think. its very noticeable.

it would be nice to have a whole set of light weight pulleys.1 can only dream lol

[Daxenth]

why would you want that?

[trevroar]

they make them for nissan's 240sx... removes weight from all accessory pulleys, I had them on my 240, they look cool cause they're in front of the car so when you pop the hood everyone will see them

[Isamu]

Originally Posted by trevroar

lol, the characteristics of an under pulley is to be smaller, hence the name. Light weight pulleys are just has you said, lighter. RRE's pulley is what it says it is, a light weight under drive pulley.

under doesn't mean "smaller" it means BELOW, which is a characteristic of weight aswell... ergo, an underdrive pully could just be lighterweight..

it DOESN'T need to be smaller.. just lighter.. 300zx UDP are simply lighter, not any smaller.. now and ODP is bigger..

[trevroar]

I believe under means as in under rotation... meh, what do i know.. read this

Underdrive pulleys - Wikipedia, the free encyclopedia

[Isamu]

Originally Posted by trevroar

I believe under means as in under rotation... meh, what do i know.. read this

Underdrive pulleys - Wikipedia, the free encyclopedia

i mean under as a word in general.. lol
and I guess i am over speaking... lol
I was assuming they were way to small..

Originally Posted by Isamu the ass

an underdrive pully could just be lighterweight..

it DOESN'T need to be smaller.

I said it doesn't need to be smaller, I have seen them just as a lighter replacement...
I understand the idea of making them spin slower, but if your doing heavy electronics, you should choose a ODP, instead of an UDP

[trevroar]

Ahh i see what you are saying.. under as in being the bottom most pulley which is always the case for the crank pulley