Does anyone offer an under drive pulley set for the 2.5 and what are opinions on if it would add anything. No duke haters please! Thanks

They don't make a kit for 2.5 that I know of.
Can cause more problems than help in most cars.
if car uses SI alt, Get more power at less engine load by switching to CS alt.

See my Cave, Watt Story and CS Alternator

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

[This message has been edited by theogre (edited 06-29-2024).]

RESPONDING TO AN OLD THREAD...

Updating this link in case someone finds this search, I found a fit here: https://www.fiero.nl/forum/...HTML/147741.html#p18

If the pulley is an under-drive set then the pulleys would need to be larger so the engine wouldn't be driving the water pump and alternator as fast BUT the larger pulley requires more power to drive. Not sure that these pulleys provide anything positive.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

"Power pulley" is a bigger crank pulley & longer belt(s) to fit that to slow down most to all things getting belt power for whatever jobs.
Covered in cave Watt Story w/ some common problem have this hype crap on a street car.

"Overrun / Decoupler" pulley in link just above is not same thing!
If this pulley is same size as OE pulley, does Nothing to Alt RPM.
If this pulley is Smaller then OE pulley, Speed Up the Alt RPM & very likely the Alt will Fail because spins faster all the time or even hit Alt's "Red Line" that mean hit or goes over Alt's max RPM that eats the bearings & more when bearing dies.
If this pulley is Bigger then OE pulley, Slows Down the Alt RPM & have same problems as "Power Pulley" causing Low Volts, Low Amps or both.

This is also covered in Watt Story.

Then why "Overrun / Decoupler" pulley... Simple to think like Shocks in car suspension that tries smoothing out impulse loads on a belt.
And Like Shocks/Struts will wear out & when does will have alt problems to start. More so making max amps as alt will behave has loose belt then pulley heats up & slips more or Fail completely. This is Part of Why almost no manufacturer puts this in a vehicle including Very High $ Models available to "the Public" to biggest trucks.

[This message has been edited by theogre (edited 06-29-2024).]

Sigh... I totally misread this post when I was doing a search for decoupler pulley. This came up and I responded to it.

Yes, what I posted is definitely not an underdrive pulley!