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Old 10-21-2006, 02:37 PM   #1
ripvw
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Default Cobb lightweight main pulley

finally pulled the trigger on installing a lightened pulley. Originally ordered a Static-X, but they had some manufacturing issues at the time and it was unavailable. They I looked at getting a Perrin from Dave @ Oakos - not a Perrin fan, but I am an Oakos fan - but Dave was also out of stock at the time, so I paid the extra bucks - $135 and got the Cobb in gold from GTWorx. Cobb's pic here:

http://cobbtuning.com/wrx/images/pulley-hi-res.jpg

and here is their description of it:
"CAD designed and CNC machined from billet 6061-T6 and hard anodized for a long lasting finish. Directly replaces the factory main pulley. Built to the factory diameter as to not underdrive your accessories. Drive belt surface precision machined EXACTLY to specifications provided by OEM belt manufacturer to ensure long belt life. Timing notch identical to factory pulley. Weighs 1.2lbs, over 4lbs lighter than the factory pulley for improved engine acceleration."

I liked the Cobb design when I first saw it - it look well engineered - and I am now firmly in the camp that can feel the difference in losing a few pounds off the main pulley. In the last couple of weeks, I have reduced 4lbs. of unsprung and rotational weight off each corner by going from RE070's to PS2's, then the pulley, and now a Prodrive axleback. I noticed a slight difference in acceleration "feel" from a dead stop with the Michelins, but the difference provided by the pulley is far more obvious. The engine revs more freely and seems to have more available power in every gear. Not an earthshaking difference like I just cranked up the boost - that's coming next month - but a noticeable and worthwhile difference nonetheless. The Prodrive sounds great, but I doubt it's adding much more hp to the equation, so I credit most of the difference to the pulley.

Shifting is a little easier too, but I just upgraded my factory STI shifter with a Kartboy lever and TIC pivot bushing - Kartboy shifter bushings already installed - and so that may account for some of the difference there.

now @ 65k, my engine has taken on some renewed life. Nice product - and thanks to GTWorx for shipping it out so quickly. My first purchase from them was a very positive experience.
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Old 10-23-2006, 08:50 PM   #2
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did you have any check engine lights?
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Old 10-24-2006, 10:15 AM   #3
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Quote:
Originally Posted by only1agam View Post
did you have any check engine lights?
no CELs
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Old 10-27-2006, 01:57 PM   #4
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I too am a firm believer in reducing unsprung weight on the car. I figure. that this weight improves acceleration everywhere, not just in one spot or dies off according to tuning.
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Old 11-30-2006, 03:32 PM   #5
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I too believe in this and am considering doing this as a christmas present, but I want to find out if anyone has gotten the cel that people are mentioning here and there. I know the op hasn't, but anyone else get one? Obviously running a flywheel that is light along with this would make a cel much more likely, but anyone without an aftermarket flywheel?
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Old 12-01-2006, 10:21 PM   #6
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I'd be curious to know what harm (potentially) could be caused by discarding the harmonic balancer and replacing with the CNC pulley? Any thoughts out there.
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Old 12-02-2006, 07:46 AM   #7
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Quote:
Originally Posted by gagliano View Post
I'd be curious to know what harm (potentially) could be caused by discarding the harmonic balancer and replacing with the CNC pulley? Any thoughts out there.
No harm the car has no harmonic balancer in the pulley. This is from the faqs. Isn't replacing the stock harmonic damper (pulley) bad? Subarus do not come with a harmonic damper or balancer like some other vehicles do. For other manufacturers' vehicles, this is a legitimate concern. Proof:

"Thank you for your patience as I checked with our Technical Services Department regarding your message below. They advised that the crank pulley is a pulley and nothing else. It is not used as a harmonic damper/balancer.

Thanks for the opportunity to be of assistance. If you need any future assistance, please feel free to contact us again."

Best wishes,

John J. Mergen
Customer Service Department
Subaru of America, Inc.
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Old 04-12-2007, 07:38 PM   #8
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Has anybody ever dyno'ed this pulley or one like it? I have one and have had it for about a year now, but I have never been able to find a dyno on a liteweight pulley letalone the Cobb pulley that I like so much.
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Old 04-12-2007, 08:00 PM   #9
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Quote:
Originally Posted by 05_WRX View Post
Has anybody ever dyno'ed this pulley or one like it? I have one and have had it for about a year now, but I have never been able to find a dyno on a liteweight pulley letalone the Cobb pulley that I like so much.
Not a dyno, but it might help understand the effects a bit:

http://forums.nasioc.com/forums/show....php?t=1145796
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Old 04-12-2007, 08:58 PM   #10
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^^^^I seen that when I searched. Perrin says that their pulley made like 10hp. Is there any bit of that true?
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Old 04-12-2007, 11:40 PM   #11
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The light weight pulley actually does not make any power...It just takes the amount of power it took to rotate the extra weight of the pulley and allows the power to be put toward the wheels. Make sense?
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Old 04-13-2007, 03:21 AM   #12
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It technically should make some wheel power but no increase in flywheel or engine horsepower. It just makes it easier for the engines to rev under all conditions.
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Old 04-13-2007, 09:36 AM   #13
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Quote:
Originally Posted by 06grayrex View Post
The light weight pulley actually does not make any power...It just takes the amount of power it took to rotate the extra weight of the pulley and allows the power to be put toward the wheels. Make sense?

I have been making high horsepower drag cars for over 10 years now. We lighten the engine internals to make more power. The pulley is connected to the crank. So changing the pulley takes weight off the crank, for every pound we take off the crank we get 2-3 horsepower. Make sense?
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Old 04-13-2007, 12:50 PM   #14
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Just to clarify.

Lowering weight in the motor, (like with a pulley) reduces sprung weight. Unsprung weight is whatever the suspension doesnt support.

Things like lateral links, wheels/tires, and brakes are considered un-sprung weight. That is because their weight is not supported by the suspension, where as the motor, chassi, and most of the drive train is sprung weight.

Last edited by parker/slc/gc8fan; 04-13-2007 at 01:18 PM.
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Old 04-13-2007, 01:13 PM   #15
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Quote:
Originally Posted by parker/slc/gc8fan View Post
Just to clarify somthing that was posted incorrectly (dont want to be mean)

Lowering weight in the motor, (like with a pulley) reduces sprung weight. Unsprung weight is whatever the suspension doesnt support.

Things like lateral links, wheels/tires, and brakes are considered un-sprung weight. That is because their weight is not supported by the suspension, where as the motor, chassi, and most of the drive train is sprung weight.
I think he was saying his wheel/tires were what changed his unsprung weight. The pulley he said reduced his rotational weight.
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Old 04-13-2007, 01:18 PM   #16
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Quote:
Originally Posted by Spectre23 View Post
I think he was saying his wheel/tires were what changed his unsprung weight. The pulley he said reduced his rotational weight.
Gee, thanks

See post # 4.

Last edited by parker/slc/gc8fan; 04-13-2007 at 01:32 PM.
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Old 04-14-2007, 12:08 AM   #17
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Quote:
Originally Posted by 05_WRX View Post
I have been making high horsepower drag cars for over 10 years now. We lighten the engine internals to make more power. The pulley is connected to the crank. So changing the pulley takes weight off the crank, for every pound we take off the crank we get 2-3 horsepower. Make sense?
I understand that your dyno will show more horsepower and torque that your engine had the potential to make, but the heavier parts were absorbing (or limiting) power output. Now that makes sense.
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Old 04-14-2007, 09:54 AM   #18
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Quote:
I understand that your dyno will show more horsepower and torque that your engine had the potential to make, but the heavier parts were absorbing (or limiting) power output. Now that makes sense.
^^^^^^^^^^^^^^^^^NOPE^^^^^^^^^^^^^^^^^^

When you make an engine more efficient with heads, exhaust, cams, internal component mass reduction, intakes, nitrous, ect. you make more horsepower. By your thinking the engine was just limited because it did not have nitrous already. The power was there it was just limited?
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Old 04-15-2007, 02:57 AM   #19
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i have an 06 2.5i wagon and this was my first upgrade. on an n/a car it made a huge differance, i have made many mods since but the cobb product it defffinatly worth every penny,us n/a cars feel this kind of upgrade in a big way
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Old 04-16-2007, 01:43 PM   #20
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Quote:
Originally Posted by 05_WRX View Post
^^^^^^^^^^^^^^^^^NOPE^^^^^^^^^^^^^^^^^^

When you make an engine more efficient with heads, exhaust, cams, internal component mass reduction, intakes, nitrous, ect. you make more horsepower. By your thinking the engine was just limited because it did not have nitrous already. The power was there it was just limited?
I may be wrong, but I don't completely agree with that and here's why. Heads, exhaust, cams, intakes, and nitrous all increase the amount of air flow and the subsequent volume of fuel injected and therefore a larger explosion and more power, whereas a lightened component should be easier to turn as it is more efficient, and therefore doesn't take energy from the explosion that could be used to turn the wheels and use it to rotate the heavier engine rotating mass. At WOT and X rpm you are still getting the same flow through the engine.
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Old 04-17-2007, 04:48 AM   #21
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Quote:
Originally Posted by 05_WRX View Post
^^^^^^^^^^^^^^^^^NOPE^^^^^^^^^^^^^^^^^^

When you make an engine more efficient with heads, exhaust, cams, internal component mass reduction, intakes, nitrous, ect. you make more horsepower. By your thinking the engine was just limited because it did not have nitrous already. The power was there it was just limited?

^^^^^^^^^comparing apples to oranges, not apples to apples^^^^^^^^^^^^^^^^^

The thing is that we're talking about the effects of lightening/lighter parts, not introducing power adders. We are not talking about increasing the effiecency of air flow, or parts that will allow more air and fuel to the combustion process. With everything being the same and the only part that is added is something the reduces the weight of the rotating assembly, means the engine has always had ability to produce that power but couldn't because of the extra weight/mass it had to turn.
Take care,
06grayrex
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Old 04-20-2007, 09:35 AM   #22
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Okay, okay, the point is it does make/allow you to go faster. That is a fact.
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