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Underdrive Pulleys 

 

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 Post subject: Underdrive Pulleys
Posted: Tue Sep 12, 2006 11:36 am 
Getting Side Ways
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Could someone please explain..

what are they exactly ?
what do they do?
what are the benefits of using them?
what are the negatives of using them?

 

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Posted: Tue Sep 12, 2006 11:47 am 
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Under drive pulleys are smaller diametre pulleys for your ancillaries such as Power steer, a/c, water pump and alternator. Because they are smaller pulleys the engine can drive them at a lower speed, which means less power is sapped by these items. It does mean that they become less efficient. So your car becomes harder to steer at lower speeds, the alt doesn't charge the battery at low speeds, etc.

Generally if you were looking at these you would already have the a/c disconnected and maybe an electronic water pump. Who needs power steer anyway it is only noticable around carparks so take that out. So it is really only the alternator you are talking about. If you were doing it for a drag strip you just wouldn't run an alternator at all.

You would probably gain maybe 10kw or so, depending on engine speed and the load that these devices are running at.

 

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Posted: Tue Sep 12, 2006 12:35 pm 
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I have 20% underdrives, and I cannot notice any difference in my power steering or anything. The factory divert more than enough power to supply air-con etc Cars have to be designed to power every accessory on max - air, radio, lights, power steering and still recharge the battery. The main gain is low end power and torque. Very cheap and good mod...

 

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Posted: Tue Sep 12, 2006 1:02 pm 
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how much roughly for the kit? i imagine fuel savings and such too?

 

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Posted: Tue Sep 12, 2006 1:16 pm 
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Underdrive + pully was about $300 for my car. Dont know about fuel savings, cos I give it to my car. I guess there would be, more around town though.

 

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Posted: Tue Sep 12, 2006 1:52 pm 
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Andre wrote:
I have 20% underdrives, and I cannot notice any difference in my power steering or anything. The factory divert more than enough power to supply air-con etc Cars have to be designed to power every accessory on max - air, radio, lights, power steering and still recharge the battery. The main gain is low end power and torque. Very cheap and good mod...


Its funny you say that because as far as the I6 goes, apart from the one company that sells them, virtually everybody else says the pulley speeds on the I6 are spot on and you get sfa gains from them. I know herrods made prototype underdrives and couldnt get any gains from them hence they never went into production.

Id really like to see a 1/4 mile pass same car with and without underdrives to get a realistic idea as to what they are worth.

 

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Posted: Tue Sep 12, 2006 2:19 pm 
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BPT have them, but they are expensive, http://www.norcom.net.au/~bpt/Ford%20un ... ystems.htm
I dont know what brand mine is, but it was recommended.

 

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Posted: Tue Sep 12, 2006 3:56 pm 
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You can only get them for the 8s, not the i6.

As for the auxiliary, theres no lost in functionality. it just creat less work or lost of power to the engine as you would normally get with a standard pully.

 

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Posted: Tue Sep 12, 2006 6:09 pm 
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there was a patition on fordforums a while ago (which i put my name down on) in the harrod section, but there wasnt enough want for it :(

 

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Posted: Tue Sep 12, 2006 6:13 pm 
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MacGyver wrote:
Under drive pulleys are smaller diametre pulleys for your ancillaries such as Power steer, a/c, water pump and alternator. Because they are smaller pulleys the engine can drive them at a lower speed, which means less power is sapped by these items. It does mean that they become less efficient. So your car becomes harder to steer at lower speeds, the alt doesn't charge the battery at low speeds, etc.

You would probably gain maybe 10kw or so, depending on engine speed and the load that these devices are running at.


The crank pully is smaller and the ancillaries are larger.
The ones I have fitted are for the crank (smaller) the alternator (larger) and water pump (larger).
But otherwise what you said is true.

 

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Posted: Tue Sep 12, 2006 6:59 pm 
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I would have thought if there are ones for BA 6's, there must be ones for older 4L's

 

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Hopefully soon: 4.11 LSD, Crow cams, BF XR6T valve springs

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Posted: Wed Sep 13, 2006 12:36 pm 
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Andre wrote:
I would have thought if there are ones for BA 6's, there must be ones for older 4L's


yeha same??

also wouldnt the ba underdrives that BPT sell fit an ef for eg?? they look pretty much that same
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Posted: Wed Sep 13, 2006 9:17 pm 
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You would think that they would be similar enough, they could quickly design them for the other Ford 6's.

 

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BA Falcon XT 6cyl: extractors, exhaust, cat, SS Inductions throttle body & CAI, K & N air filter, 20% underdrives, thermostat, CAPA Flash Tuner/Custom tuned, trans cooler
Hopefully soon: 4.11 LSD, Crow cams, BF XR6T valve springs

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Posted: Wed Sep 13, 2006 9:38 pm 
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the ba and au balancer are the same ,dunno about e series though
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