Underdrive Pulley what do they do?

[bigdogdazza]

I have recently purchased a 25% undrive pulley kit for my ve ss ute and would like some feedback from anyone who has fitted one to a ve....what exactly are the benefits or gains and is there any downside to fitting these?

[Evman]

It spins the accessories slower which produces less resistance to the crank. They don't actually MAKE more power, they allow more power to be delivered to the driveline.

[Kuzman89]

yeh, gives you better fuel economy and makes ur car rev better I heard, ive been thinking of getting a 20% UP for my sv6, but dont really know where to go

[planetdavo]

I have recently purchased a 25% undrive pulley kit for my ve ss ute and would like some feedback from anyone who has fitted one to a ve....what exactly are the benefits or gains and is there any downside to fitting these?

You are asking these questions after buying one? :confused:
As people say, they spin things slower, but you do need to understand there is a reason things originally spin at the speed they do. The belts do of course spin fairly unimportant things like a water pump, an alternator to charge the battery etc....
Translation: Best you keep the revs up, or send it back and get a refund if you don't.

[SSV8TE]

Had an underdrive on mine for over 12 months and never had a problem from it whatsoever. They are slightly lighter than the stocker too so removing inertia and less restriction on accessories means you can achieve higher throttle response. In saying this lightening the harmonic balancer and if later the flywheel does come with some disadvantages one being engine gets a little shakey at cruise speeds. This can be improved through the tune but all in all i vote +1 for one. They help in the long run with a complete package of mods.
Best of luck,
Andy.

[Lincoln87]

only time i personally would consider fitting one would be if i was getting a cam jobby job at the same time.


...depends where your up to in terms of mods. but money could be spent else where first for better money for power.

[disco364]

i got a vy ss, and i put one on because after getting a rebuilt auto with a shift kit, when it decided to change gears at high revs the fan belt was slipping and then squeaking heaps

[SirNemesis]

You need to change to a smaller belt when changing to an underdrive pulley...