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Discussion Starter · #1 ·

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Lighter weight or smaller diameter pulley means it rotates faster which will cause the rest of the systems on the pulley to spin faster as well.. It will let you rev faster on the Cobalt.. there's been a lot of debate on these over the years.. Some say it will cause your other systems to wear out faster because its spinning faster than what the factory recommends. i.e. your A/C unit
 

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Discussion Starter · #3 · (Edited)
This is just alternator then there's the crank pulley. So I guess if you have JUST an alt pulley, it will make it spin faster but wont spin as fast as if you had JUST a crank pulley? i guess there could be no harm in having just an alt pulley as opposed to having the crank, or both. I mean it's not balanced i don't think? cause if it's something with balance, thats were you can get problems i read. that's why i won't get the crank one
 

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The less mass there is to rotate the easier the pulley will spin. That's pretty much it in a nut shell (someone correct if I'm missing something or wrong). The idea that MRZ is trying to sell is that your engine will rev faster with less weight on the pulleys, which is true, but you probably won't see a real difference until you add like a lighter flywheel or something.
 

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Lighter weight or smaller diameter pulley means it rotates faster which will cause the rest of the systems on the pulley to spin faster as well.. It will let you rev faster on the Cobalt.. there's been a lot of debate on these over the years.. Some say it will cause your other systems to wear out faster because its spinning faster than what the factory recommends. i.e. your A/C unit
Admin beat me to the punch. :( lol
 

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Discussion Starter · #6 ·
i was reading this whole site yesterday i didnt save it unfortunately but a lightweight flywheel can mess the engine up too cause of more vibs
 

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i was reading this whole site yesterday i didnt save it unfortunately but a lightweight flywheel can mess the engine up too cause of more vibs
I thought the MRZ pulleys were supposed to meet the same specifications as the stock pulleys except for weight and diameter, they should still have the same amount of ribs to work with the rest of the pulleys.
 

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It says it's the same diameter so the alt will spin at the same speed...the lighter weight will in theory have less parasitic power loss especially when the alt is under load.
 

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I have both MRZ crank and alternator pulleys.

I definitely noticed faster rev's but didn't really notice any more hp.
agreed although i did find a lil bit more power was freed up

ok, so ya'll are kinda right haha
its not that it will have anymore speed to it when rotating, its that it will cause less drag when attempting to accelerate and it will take less force from the engine to keep it moving. Aka less rotational mass. It’s the same idea as getting a lightweight flywheel or lighter rims, less rotational mass. Think of it this way, tie a weight to the end of a rope and swing it around your head, feel how heavy it is? Now tie a lighter one and spin it...a lot easier ya??? the reason it doesn’t spin really any faster (as long as you don’t get the smaller diameter one) is because its still moving the same distance, think of that just like a tire size. Now, the smaller diameter can make even more power because it saves even more weight, down side is that you loose power from your alternator and such cause the belt is moving slower (crank pulley moving less distance around).
So, your accessories will never spin at any faster speed, its just that you can get them up to speed easier thus freeing up hp being lost. Aka, you will have the same crank hp but a higher wheel hp

Hopefully that makes sense...

Oh, also, you will loose some of your momentum that your engine carries, aka when you hit a hill, you may have to downshift where you didn’t before. Because not only is it easier to spool them up...its easier for them to slow down...
 

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This pulley has me a lil interested. i like small bolt ons that are inexpensive. My question is....has anyone done a dyno for this...before and after? or are their claimed hp gains from the company? I mean for 1 or 2 hp and 60 bucks....sounds like a decent deal to me. Every little bit counts with our light weight cars.
 

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This pulley has me a lil interested. i like small bolt ons that are inexpensive. My question is....has anyone done a dyno for this...before and after? or are their claimed hp gains from the company? I mean for 1 or 2 hp and 60 bucks....sounds like a decent deal to me. Every little bit counts with our light weight cars.
jn2 on css or ccf has done it, he dynoed all pullies and such. he did show a small horsepower gain with them
 

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thank you cobalt tom.... can you post results please ?
 

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here are his numbers and his quote
as you can see the UDP did add more, but in all reality, i dont see anything out of the ordinary in the dyno number, the first one was doen with 10 min break from making the drive to the dyno, the OEM lightweight got a 10-15min break after 2 consecutive pulls, which might be why the OEM got such low numbers, well the UDP got 30 min break time, as the belt was once more a ***** to put back on...i posted the best of each pulleys #, compared them to each other, like i said, i dont see anything out of the ordinary, no enought power was added, but i can say my car rev's like a bat out of hell, i let it rip on the dyno in the first gear had a big smile the whole way, car pulled like it never has before


 

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Discussion Starter · #19 ·
127hp??? WTF
 

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Thank you man, So which under drive pulley and alternator pulley gavethe best gains together ?
 
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