What's a under drive pulley?

buddy92 · 30-12-2012, 09:12 AM

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 · 30-12-2012, 09:19 AM

Ahhh the add explains it...

Quote:

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 · 30-12-2012, 09:27 AM

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

Franco Cozzo · 30-12-2012, 09:28 AM

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

**Burnout** · 30-12-2012, 09:38 AM

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

XR6T0Y · 30-12-2012, 10:13 AM

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 · 30-12-2012, 10:15 AM

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.

**Mont5.0** · 30-12-2012, 09:17 PM

Quote:

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?

FPV GTHO · 31-12-2012, 11:40 PM

Quote:

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

2011G6E · 10-01-2013, 12:05 AM

Quote:

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.

Well that all sounds great...I'm sure that on a modified engine you want less coolant flowing around...

I'm sorry, but it all sounds a little too good to be true...you're still driving the exact same amount of equipment, so it shouldn't matter if it's slower or faster...and a "light balance" is just doing away with what its there for in the first place...plenty of guys years ago snapped cranks thinking doing away with that "big heavy balance" hanging off the crank snout was a good idea...

I thought under and overdrive pulleys were only for superchargers...?

mike_nofx · 30-12-2012, 04:01 PM

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

**MercurySilver** · 30-12-2012, 04:50 PM

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 · 30-12-2012, 05:18 PM

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 · 30-12-2012, 05:23 PM

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

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Drizz06 · 31-12-2012, 12:51 AM

Quote:

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.

Linkachu · 30-12-2012, 06:37 PM

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 · 30-12-2012, 06:42 PM

Cool thanks everyone i might grab one

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Pinkbits · 30-12-2012, 07:46 PM

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

FGII-XR6 · 30-12-2012, 09:18 PM

Quote:

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 · 30-12-2012, 11:21 PM

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

buddy92 · 31-12-2012, 08:15 AM

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

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mike_nofx · 31-12-2012, 09:55 AM

Quote:

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.

Drizz06 · 07-01-2013, 10:34 AM

Quote:

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.

buddy92 · 31-12-2012, 10:15 AM

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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blue_ute · 07-01-2013, 12:16 AM

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

**cs123** · 07-01-2013, 10:52 AM

Quote:

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 · 07-01-2013, 11:59 AM

Quote:

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.

Franco Cozzo · 07-01-2013, 12:23 PM

Quote:

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.

**cs123** · 07-01-2013, 02:29 PM

Quote:

Originally Posted by Big Damo

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

The alternator is rated at what? 100 amp, So that is 1.2KW at full load.

Franco Cozzo · 07-01-2013, 02:43 PM

Quote:

Originally Posted by cs123

The alternator is rated at what? 100 amp, So that is 1.2KW at full load.

Thats the amount of power it can generate at full load, its not 100% efficient as well mind you, it takes a good effort to spin it up under 100% load, and it might not do that 100a until 2000 RPM+.

Something interesting is I wired up a pair of spot lights for my mate on his Hilux, standard carby 22R engine, when he put his lows, highs and spotlights on the engine RPM dropped a fair bit, I reckon there is a good 5KW or so just on the alternator if its loaded up.

So you've lost around 5KW on the alternator, you've also got a power steering pump and a water pump constantly working, aircon compressor when it kicks in is another.

It all adds up, especially if you're at the point where you've hit the price/performance point on where you can't go anymore without engine rebuild, you look at all the little niggling things here and there, they add up.

I'm not keen on the slowing of the water pump though with the under drive, but I guess many people here have them and their cars are obviously doing OK.