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Discussion Starter #1
Hi Guys,


so I've got a 2005 R53 with the JCW 210 kit.
I also have an ALTA 15% sc pulley and a few other power and suspension mods (intake, cam, header, c-overs etc). Recently the car has been making a slight but noticebale chirping sound and my mechanic has diagnosed it as wear from the crank pulley. So I need to have it replaced. Now I what I would like to know is whether it would be worth getting an ATI 2% dampened pulley?
Would there be noticeable gains over a standard sized pulley? And do I need to be worried about overheating or other issues? The car only gets used a few times a month and I do a couple of track days here and there. Also Im running an Airtec top mount IC.

Hope thats clear.
Any advice much appreciated.
Thanks
Matt
 

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the Airtec is going to deal with the extra heat + you have the JCW head (which isn't a big deal but has a slightly better flow); the extra 2% wont be a problem; go for it;
 

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Hey Matt, for the cost of the pulley and the enlarge, is not worth the slightly more boost plus you have to combine it with enlarged alternator pulley and a new belt! If you want dampened get an oem facelift otherwise go solid lightweight 0% to get more response and better power delivery!
 

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facelift or not, the OEM tends to fall apart; many of us have negative experience;
Hey Matt, for the cost of the pulley and the enlarge, is not worth the slightly more boost plus you have to combine it with enlarged alternator pulley and a new belt! If you want dampened get an oem facelift otherwise go solid lightweight 0% to get more response and better power delivery!
 

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Discussion Starter #7
Thanks for the advice guys….can anyone tell me what gains a +2% would be give me over the standard size?
 

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2% over on the crank will be marginally less than 2% under on the charger.

The ATI damper is about the best, but save your money and get a standard size one. It makes belt selection much easier.
If you do insist on overdriving the crank, then don't bother with a larger alternator pulley. The need for one is a falacy, the electronics inside it will self regulate the voltage.
 

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UK prices are different, the +2%, is £470 at 1320 and is £70 more than regular size.
I had one and it was just a nuisance finding belt sizes and calculating the total underdrive on the supercharger for tuning purposes etc. The second one I got was standard size which was more practical for matching different pulley sizes too. You're choice, but it sounds like you've made your mind up anyway.
 

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UK prices are different, the +2% is £70 more than regular size.
I had one and it was just a nuisance finding belt sizes and calculating the total underdrive on the supercharger for tuning purposes etc. The second one I got was standard size which was more practical for matching different pulley sizes too. You're choice, but it sounds like you've made your mind up anyway.
 

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I have the 15% s/c pulley and I originally had the ATI standard crack pulley, I recently went to the +2% ATI and I gain 1lbs of boost.
 

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what's the difference between a belt required for a 17% pulley, and one the OP would need for his setup?
Well a 17% pulley with a 2% crank will need a longer belt, I can tell you that much lol.

I have the 15% s/c pulley and I originally had the ATI standard crack pulley, I recently went to the +2% ATI and I gain 1lbs of boost.
Effectively the same as a 17% pulley and a standard crank.
Your charger is spinning 2.53 times faster than your +2 crank, a 17% pulley on standard crank would be spinning 2.54 times faster.
 

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OP has a 15% pulley; so the delicate belt size would be the one everyone gets with a 17% reduction; I really don't see how's that a problem;
Well a 17% pulley with a 2% crank will need a longer belt, I can tell you that much lol.


Effectively the same as a 17% pulley and a standard crank.
Your charger is spinning 2.53 times faster than your +2 crank, a 17% pulley on standard crank would be spinning 2.54 times faster.
 

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OP has a 15% pulley; so the delicate belt size would be the one everyone gets with a 17% reduction; I really don't see how's that a problem;
Sorry but that can't be right. There's no way the belt for a 15% reduction in supercharger pulley size together with a 2% increase in crank pulley size is the same as that needed for a 17% supercharger pulley reduction.

Even if you make the, no doubt incorrect, assumption that both stock pulleys are the same diameter the -15 +2 would be equivalent to a -13.

I may not know much about the merits of the different pulleys but I know enough maths :)
 

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On my old car with 17% sc and +2% I ran a 6pk1353. A 1360 slipped above 6k. Tight fit to get on but never slipped. I changed mine twice a year though.
 
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