I was wondering, i heard people talking about underdrive pulleys and i've seen them in magazines. But i want to know more about them to see if i should buy one instead of headers. What all do i need to buy for an underdrive pulley? Do i need new belts? Do i need to adjust timing or anything? THanks alot for your help.
Jamie

An underdrive pulley simply limits the power used for accessories, thus creating more power to the motor itself. The most popular one for the 2GNT is the AF/X available through howell. Most UDP's come with all the belts you need and cost around 250ish new. Most people seem to agree they generate about 12+HP right to the wheels for eclipse's. Do a search on this topic and you will find a ton of hits.


AEM CIA|SpiralMax|NGK Plugs|Magnecor Wires|GST Exhaust|Mirror Tint|Grillcraft grill|EBC brakes|Brembo Crossdrill/slotted rotors|Front/Rear strut bars|
Coming:55mmTB

hit up my site if u wanna read an intsall how-to...

about 8-12 whp dyno proven, and that was on a neon, and we loose more weight so the gain will prolly be more...

u will need to tighten the belts up about a weeek after install, but then if u did the install right, u will only have to replace the belts for normal maintenance...

good luck either way.

Unorthodox has a good explanation of how the power is obtained. Here is a quote from thier site:

<QUOTE>
These power gains are obtained in a few ways. First, and most important, is the weight loss. There is an average of 2.7 HP gained from every pound lost off the crank shaft. 85% of our gains are from weight loss.

Second, you are not driving any accessories with our Ultra Race crank pulley except the alternator (and water pump in some applications). The rest of the gains are from the underdriving, which accounts for about 15% of the total gains.
</QUOTE>

Alot o peeps use the AFX UDP...like me. I love it. Here's some visuals for you.

Stock pulley weight:


AFX UDP weight:


Side by side comparison. The stock one is big and steel. The UDP is small and alluminum:



ride__________95 Eclipse RS : 5 speed
power________Gude cams : AFX UDP : ram air : test pipe : Thrush glasspack
suspention___BOMZ F/R upper strut bars : ES inserts
shizzle_______AutoCommand remote start : Dual air horns : Kenwood KDC 5000 : Rampage sub
incomming___lower strut bars

nice pixxx...

>Most UDP's come with all the belts you need
>and cost around 250ish new.

Received mine from www.ptuning.com for 159.99 w/ belts.

I got my Unorthodox, before I knew of the AFX, for $212 shipped plus $30 for the Gates belts. So shop around and get the best deal...:thumbsup

I've heard if you have a system in your car and you get underdrive pulleys the wattage to the amp goes down and makes the speakers not hit as hard or perform as good than before .





99 GS OZ EDITION
MODS- Apexi N1 Catback
Progress Sport Springs
Audio- JVC CD/TAPE/MP3 Player
Pioneer XM Radio
2 Alpine type R 12s
MTX-775 Watt Amp

Future Mods-
Hahns Stage 2 Turbo Kit
17in Rims
JSP Carbon Fiber Blade or Arospeed Carbon Fiber ST wing
Carbon Fiber Vented Hood
Sparco Racing Seats
AEM Big Brake Kit
Final Drive Mod
Tansco Shift Kit
Bottom End Kit
More to come......

I have two kenwood amps 1 pushing my main speakers (front and back), the other pushing 2 tens. I will let you know if there is any difference after installing my UDP. I have read on other boards where it made no difference and that most accessories are over powered by the engine to begin with, but it would probably depend on how taxed your alternator is and how big of a system you are pushing. If you have a big system the extra 10 horsepower will not matter against the extra tonnage of multiple amps and large speaker boxes anyway, therefore a UDP would not be suggested.

Right now I have zero light dimming issues or any other tell tale signs of inadequate power response, lets keep the fingers crossed.

UDP is in and I have not noticed any difference in my stereo or lights. Car seems to rev a little faster. It may be too early to tell the affect at this point, I also think my fuel maps in the computer reset from lack of power during install. No belts squealing either.