What's a under drive pulley?

[buddy92]

Hi.

I been a lot of people talking about under drive pulleys, can someone please tell me what they are? Wiki doesn't help much.

There's on on eBay for $299 ( $25 postage ) and from what I have seen and under stood would be interested in one for my car.

This is the one I seen.

http://www.ebay.com.au/itm/BA-BF-FG-...ht_1027wt_1037

Are they worth it, and is there any dis-advantages of them?

[Jim Goose]

Ahhh the add explains it...

What do Underdrive Pulleys do? Underdrive pulley systems increase engine horsepower by reducing the amount of power required to drive external engine accessories. For example, the alternator, power steering, water pump and air compressor rob horsepower from the engine. By replacing factory-sized crank and accessory drive pulleys with a resized pulley, the accessories are slowed, resulting in more horsepower available to the drive wheels. All pulleys are manufactured from Billet Steel or Aluminum, exceeding factory quality.

But im somewhat dubious to the claim it increases horsepower

[buddy92]

Opps, sorry I missed that part. I never read down the bottom. Sorry about that Jim.

[Franco Cozzo]

Wouldn't that effect alternator charge rate, aircon, water pump performance etc, because they're now spinning slower?

[Burnout]

Yep they would, but do you need that stuff anyhow?

[XR6T0Y]

Everyone says that it will 'hurt' the engine because of something and something. I have one. I think it's great. Handling is slightly heavier which I like, AC hasn't changed etc. It reduces parasitic power loss. Not destroy the engine. They are a good mod

[XBROO]

Yeah never thought you would need that unless you were turning big revs, or of coarse blown. It won't do anything to the motor but it slows all the assessories down. Like just mention the steering might get a little heavier, aircond mighting pump as hard and the water will flow slower from the water pump.

[mike_nofx]

Dont FG owners have issues with AC not being cold enough as it is, let alone slowing down the compressor speed??

[MercurySilver]

i dont
08 g6e and i hear this all the time
put it on semi auto as low as you can go in temp(until it says low in blue) then crank the fan
been driving around on some stinker hot days in sa and it seems fine...if you keep it over half speed on the fan
drop it to around a 1/4 and its not as good
but i will say with it cranked up as soon as the car is down to like a third left int he tank it seems to chew thru the juice (but that might be me just imagining things)

[Linkachu]

They are good, had one on my EF XR8 and you notice the motor is a little more free.

The only reason its frowned upon is on idle they do spin a little slower, but when driving its no different.

[buddy92]

Ive had no problems with my air con. Can a average joe install one?

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[Linkachu]

Its not simple, but its not hard. My EF the Radiatior had to be taken out, it was sort of a 2 man job but not really.

Should take 2 hours or less. Instructions will come with it just follow those

[buddy92]

Cool thanks everyone i might grab one

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[Pinkbits]

I'm sure the late model AU XR8 had them fitted from factory.

[Mont5.0]

Originally Posted by XBROO

Yeah never thought you would need that unless you were turning big revs, or of coarse blown. It won't do anything to the motor but it slows all the assessories down. Like just mention the steering might get a little heavier, aircond mighting pump as hard and the water will flow slower from the water pump.

I've been told when putting blowers on late model cars that under drives shouldn't be used?

[FGII-XR6]

Originally Posted by Pinkbits

I'm sure the late model AU XR8 had them fitted from factory.

all AU 5.0L were underdriven to the best of my knowledge

[Windsor220]

I think they were underdriven but not quite as much as the aftermarket ones.

[Drizz06]

Originally Posted by buddy92

Ive had no problems with my air con. Can a average joe install one?

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You will most likely need a puller but apart from that should be a easy job.
Buy the full kit with replacement upgraded idler pulleys and change them to.

[buddy92]

Do you have a link for the kit? I could only find the one I linked.

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[mike_nofx]

Originally Posted by buddy92

Do you have a link for the kit? I could only find the one I linked.

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I had to look up what a GT-P 3110 was. Thought it was a new FPV.

[buddy92]

Lol I tried getting it off. Everytime I write i gotta delete it manually. Signature is off but still comes up when i post.

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[FPV GTHO]

Originally Posted by Mont5.0

I've been told when putting blowers on late model cars that under drives shouldn't be used?

I've heard the turbos don't like them for harmonic reasons and with a supercharger I've heard you then need to overdrive the blower.

For the minimal gains of the under drive vs the significant gains of the blower, I wouldn't worry about it

[blue_ute]

If your staying na the underdrives are good but you may need a tune to get the most of it I picked up 10 rwkw so I think it's worth 300 dollars best bang for buck so far

[Drizz06]

Originally Posted by buddy92

Do you have a link for the kit? I could only find the one I linked.

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Sorry mate the one you linked is the correct kit.
Speak to Justin from Tuff car parts directly and he'll do you a deal.
He is on the forums in sponsor section.

[cs123]

Originally Posted by blue_ute

If your staying na the underdrives are good but you may need a tune to get the most of it I picked up 10 rwkw so I think it's worth 300 dollars best bang for buck so far

I don't understand how your 100W alternator and water pump that are driven from your belt would use a total of 10 KW.

[Drizz06]

Originally Posted by cs123

I don't understand how your 100W alternator and water pump that are driven from your belt would use a total of 10 KW.

Power steering also sap's power.
From my understand it also helps engine spin up faster by reducing drag therefore giving you better starts etc.
Should also reduce fuel usage at low speed by a small amount.

[Kable72]

Also, he did say he got a tune with it as well which would have picked up more power. It's really only there to take some weight off the crank so it spins up faster. That in itself is enough to fool the dyno in picking up 10rwkw

[Franco Cozzo]

Originally Posted by cs123

I don't understand how your 100W alternator and water pump that are driven from your belt would use a total of 10 KW.

Anything driven from a belt off the crank shaft costs you power, hence the invention of EPAS now hitting most modern cars and the new Ranger with its fancy alternator which turns on/off, or the VE series cars which free spin the alternator on WOT.

With an alternator, it free spins easily, but when you load it up by turning on more electrical stuff it gets harder to turn.

[mike_nofx]

Originally Posted by cs123

I don't understand how your 100W alternator and water pump that are driven from your belt would use a total of 10 KW.

I know right??

And you're not totally removing them from the system, just reducing their speed by what, 15%? So a 15% reduction creates 10kw.

What does totally removing them from the system do, create (10kw/15X100%) 66kw?

I imagine dyno runs are done with AC off (so minimal losses), and wheels not steering (power steer pump not working hard?) so 10kw gain sounds huge.

Yes a tune may give best results, but possibly the tune alone increased power by 9kw, and the underdrives 1kw. who knows.

[Drizz06]

Doesn't matter what the dyno says!
Any improvement for under $300 is fantastic.
And that's power added by improving efficiency and not adding any stress to the motor or driveline.

Also lol @ 100w alternator! How can you comment on something you do not understand.