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Discussion Starter #1
Hi there!

I was wondering whether you guys had tested your lightweight crank pulley on the 2008 impreza. I have heard that the idle pulley assembly is absent from the 2008 engine, and that a new self-tensioning belt replaces the previous belt. Have you had any luck getting the belt off without destroying it and reinstalling it with the lightweight crank pulley?

Hopefully it works, as paying 80 for a new belt on top of the lightweight crank pulley cost would be a bit lame... If you guys have figured out how to work that magic, I'll be forever in your debt...
 

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in order to the belt off you have to cut it then when you purchase the new belt from subaru it comes with the tool to install it back on. I got my belt from Jamie at SGP for like $56 plus shipping. The bad news is that the belt and the pu;;ey are sitting in m,y computer room to get installed someday.
 

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The whole idea of swapping out the stock pulley for a lightweight pulley is to decrease rotational inertia... adding a tensioner pulley is just going to add weight back again. Why bother? Do it the right way and just install a new cut-off belt.
 

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I think the idea is to reduce rotational inertia not necessarily remove overall weight from the car. I read somewhere that putting the lightweight crank pully on our car is equivalent to removing 100 lbs. of weight from the vehicle.
 

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Discussion Starter #7
0000021660 said:
I think the idea is to reduce rotational inertia not necessarily remove overall weight from the car. I read somewhere that putting the lightweight crank pully on our car is equivalent to removing 100 lbs. of weight from the vehicle.
Those are pretty bold claims. I'm sure that it depends on the weight of the oem pulley and the weight of the lightened pulley. In my experience pulleys aren't the best place to invest your money if you are looking for performance. Most people who get them always seem to have trouble feeling a difference even on the butt dyno. Better to throw your money into upgrades for that larger turbo. Even if I had the money for the pulley and nothing else to spend it on, I still wouldn't get the pulley. That's just me though.
From what I've read, the OEM pulley is about 4.5-5 pounds. The lightweight pulleys range from about 1-1.6 pounds. Also, these are more of interest to the N/A crowd. Since we don't have a turbo, we lose a larger percentage of our power into that pulley. As far as how much of a difference it makes - there is a video somewhere of someone comparing revving to redline with the lightened pulley overlaid on the OEM pulley. This was a wrx and it still made a noticeable difference; it didn't make or break the car, but it seemed to rev about 5-10% faster. Since we don't have the turbo, it should make an even larger difference for us. I agree that it probably won't be a night and day difference, but for about $130, it isn't very expensive.
 

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WRX is right. Any resistance an idler pulley gives to the belt is pretty much negligible. It is a very light pulley and it rotates very freely. All its there to do is create tension without slowing the belt down. Is there some resistance? sure, the world isnt perfect. But removing 4lb from the crank pulley and removing a 2 ounce free-rotating idler pulley are completely different. I guarantee that you could not find a dyno difference between idler pully and the new shrink belt.
 

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in order to the belt off you have to cut it then when you purchase the new belt from subaru it comes with the tool to install it back on. I got my belt from Jamie at SGP for like plus shipping. The bad news is that the belt and the pu;;ey are sitting in m,y computer room to get installed someday.
you do NOT have to cut the belt! it can be easliy re-used. i just cranked over the engine with a rachet, tranny in neutral, @ the crank pulley and guided it off. replaced the stock pulley w/ the light weight one and guided it back on again. no need for a tensioner or tool or cutting.
 

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Those are pretty bold claims. I'm sure that it depends on the weight of the oem pulley and the weight of the lightened pulley. In my experience pulleys aren't the best place to invest your money if you are looking for performance. Most people who get them always seem to have trouble feeling a difference even on the butt dyno. Better to throw your money into upgrades for that larger turbo. Even if I had the money for the pulley and nothing else to spend it on, I still wouldn't get the pulley. That's just me though.
At first blush I don't believe it either, but here it is from the Perrin website

"Weight reduction is key to making the best use of any available HP and torque. In no place on our vehicle is this more important than the rotating mass found in the engine. The PERRIN PerformanceTM Crank Pulley is 4-pounds lighter than the stock crank pulley. This reduction is equal to removing more than 100 lbs of vehicle weight! "

I wouldn't notice 100 lbs. missing off the vehicle. My wife is 100 lbs. and it's not noticeable when she's in /out of the car. I look at this mod as the thing to do when you have $150 burning a hole in your wallet and nothing else to spend it on.
 

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hey andy lust letting you know i got my crank pulley installed yesterday. cost me about $90 for installation on my AT. they put on the new tensioner and threw on an old toyota belt (all japanese belts are identical and made by the same company, and for some reason the one i had was too big). neway i feel a difference in my engine, 4-6 RPM goes by faster. ive also noticed the car slowing down quicker when i lay off the accelerator on the highway, which means there really is a decrease in inertia here (same as taking a lot of weight out of the car). i couldnt believe how heavy the stock pulley was.

anyway good luck!
 

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Discussion Starter #16
hey andy lust letting you know i got my crank pulley installed yesterday. cost me about for installation on my AT. they put on the new tensioner and threw on an old toyota belt (all japanese belts are identical and made by the same company, and for some reason the one i had was too big). neway i feel a difference in my engine, 4-6 RPM goes by faster. ive also noticed the car slowing down quicker when i lay off the accelerator on the highway, which means there really is a decrease in inertia here (same as taking a lot of weight out of the car). i couldnt believe how heavy the stock pulley was.

anyway good luck!
Awesome! Thanks for the info!
 

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Why is this discussion in the Rallitek section??? ??? This is a convo that's best shared in the engine tech section, yeah?
 
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