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Old 01-10-2005, 06:41 PM   #1
b_DuB13
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Question Underdrive pulleys?

Hate to add on to all the other noobie questions, but underdrive pulleys are one thing, among many others, that I would like to know more about, seeing that they keep showing up on cars' mods lists...
The basics, for starters. I haven't a clue about what they do.
Diagrams and long lengthy explanations are welcome.
Thanks.
-b
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Old 01-12-2005, 02:26 AM   #2
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Yeah, I heard that they are on the top of the list for replacment, and I don't know what they do. I would also like to find out.
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Old 01-12-2005, 02:45 AM   #3
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Quote:
Originally Posted by b_DuB13
Hate to add on to all the other noobie questions, but underdrive pulleys are one thing, among many others, that I would like to know more about, seeing that they keep showing up on cars' mods lists...
The basics, for starters. I haven't a clue about what they do.
Diagrams and long lengthy explanations are welcome.
Thanks.
-b
Quote:
Originally Posted by RusMan
Yeah, I heard that they are on the top of the list for replacment, and I don't know what they do. I would also like to find out.
The simplest explanation I can give is this. The engine in your car drives several accessories by means of a belt. The most common are the A/C compressor, P/S pump, water pump and alternator. The belt is driven by the crankshaft pulley. Regardless of engine speed the accessories are always driven at the same ratio. This is based on the diameter of the crank pulley and the diameter of the accessory pulley. Driving the accessories takes power.

All an underdrive pulley is is a smaller diameter crank pulley so the accessories turn slower in relation to engine speed. By turning them slower less power is used for that purpose and more power is available to move the car. The downside is that because the accessories are running slower, there will be reduced output that in some cases MAY cause overheating, low charging system output, etc. It should also be noted that in some underdrive pulley kits, in addition to a smaller crank pulley there will be larger accessory pullys further reducing the power useage.

The best analogy I can come up with is to go ride your 10 speed bike (steal one if you have to). As you shift up in the gears you have to work harder but the bike goes faster. As you downshift, pedaling is easier but you go slower. That is the concept of underdrive pullies.

Comprehendo? If not just ask.
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Old 01-12-2005, 04:39 AM   #4
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one of my favorite ways about not having to worry about the pullies, get rid of PS and AC... who needs em... thats what i did on the corolla, and the revs got up noticably faster...
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Old 01-12-2005, 04:43 AM   #5
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Yea my car doesn't come with PS, then the AC stopped working so I just took everything out, Works very well.
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Old 01-12-2005, 04:52 AM   #6
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I can see dropping the A/C but the powersteering stays. Big block mopars don't notice it.
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Old 01-12-2005, 04:55 AM   #7
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Yea but my 1.3 liter CRX does, or would, If it had PS that is.
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Old 01-12-2005, 03:25 PM   #8
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i actually dont like PS so i try to take it out... luckly the civic didnt come with PS
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Old 01-15-2005, 03:02 AM   #9
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what drives the belt in the engine.
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Old 01-15-2005, 03:06 AM   #10
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Quote:
Originally Posted by CarEXPERT
what drives the belt in the engine.
Read the third post in this thread until it becomes clear. The purpose of all this typing is to share information but it only works if you read it.
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Old 01-15-2005, 04:08 AM   #11
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Ohh.. sorry. What is a crank pully though. i know what a crank is but whats a crank pully?
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Old 01-15-2005, 06:05 AM   #12
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Quote:
Originally Posted by CarEXPERT
Ohh.. sorry. What is a crank pully though. i know what a crank is but whats a crank pully?
You do? Tell me, what is a crank?
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Old 01-15-2005, 06:36 AM   #13
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a crankshaft is a shaft that spins because the piston goes up and down to spin it and the shaft is connected to the flywheel and then to the clutch and the driveshaft and then the wheels. Am i right? correct me Sir if im wrong. But i dont know what a crank pully is or a crankwalk
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Old 01-15-2005, 03:02 PM   #14
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Quote:
Originally Posted by CarEXPERT
a crankshaft is a shaft that spins because the piston goes up and down to spin it and the shaft is connected to the flywheel and then to the clutch and the driveshaft and then the wheels. Am i right? correct me Sir if im wrong. But i dont know what a crank pully is or a crankwalk

I'm just curious, why is your login name "carEXPERT" if you don't know what a crank pully is?
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Old 01-15-2005, 05:07 PM   #15
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Quote:
Originally Posted by DodgeRida67
I'm just curious, why is your login name "carEXPERT" if you don't know what a crank pully is?
why don't you guys just help him out instead of being so negative. he's just asking for help. If you don't want to do that then don't respond to the post
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