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Old 07-13-2012, 09:29 PM   #101
Racebrewer
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Hi Guys,

I have followed the pulley discussions on many forums over the last 20 years. IMHO, The discussions come down to two things.

1. Lots of theory and text book explanations of how different types work. Which is good. Lots of mis-understanding out there.

2. If someone has bearing issues, they look for something to blame it on (right or wrong). If the crank had a lightweight pulley, that must be to blame ! ! ! Human nature AND not necessarily wrong.

OTOH, In a Mazda Miata forum it was commented that a ltwt undampened pulley didn't cause any issues unless there was also an aftermarket turbo kit installed.

So, here is my 2 cents and a discussion point. Is it a detonation issue? Does a heavier and or dampened pulley help when there is increased detonation due to other causes? If there is no detonation problem are there no pulley concerns?

I can see that the additional weight would keep the crank from pounding the bearings.

Any thoughts?

John
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Old 09-18-2012, 04:57 PM   #102
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Was wondering if any of you who run the light weight pulley notice a drop off in power with the A/C on? I know all cars lose power as the the A/C kicks in pulling power to it's own belt, but my wrx just plain dies.

My theory is with a lighter crank pulley the A/C belt slows it down a bit more compared to if it had a heavier(stock) pulley generating more momentum.

That or I could be way off base with my car, it just seems my car loses a significant amount of power with the A/C blowing.
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Old 05-11-2013, 09:06 PM   #103
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Thank you. Perfect info!
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Old 05-15-2013, 01:15 AM   #104
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You are a true guru, a master at presenting information.
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Old 01-07-2014, 10:58 PM   #105
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Quote:
Originally Posted by Unabomber View Post
The Vishnu method is the "best" method, so use it.
Hey Unabomber, i have a aftermarket lightweight exedy flywheel and clutch its still stage 1. And According to exedy's website its a OEM replacement part's. So the question i am getting at is, if my tranny is lighter than stock and i install a aftermarket lightweight pulley(i am looking at grimmspeeds 2.2lbs pulley) will that lack of rotational mass be a problem? Like you said the solution would be to re install the OEM pulley if there was a problem, but i am having trouble finding information on light weight trannys with lightweight pulleys. Thanks for the help
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Old 01-08-2014, 08:02 AM   #106
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The core of the problem, after years of guesswork is in the lightweight flywheel itself. They can cause missfire CELs. Adding a lightweight pulley now or later will not affect this. So if you are not throwing a missfire CEL now, the lightweight pulley addition should not affect it. Some cars will not throw a CEL with a lightweight flywheel though so its a hit or miss thing. If you want a lightweight pulley, send me a PM with a pic of a hot chick and I can get you a source for a discounted one.
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Old 01-08-2014, 08:57 AM   #107
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Quote:
Originally Posted by Unabomber View Post
The core of the problem, after years of guesswork is in the lightweight flywheel itself. They can cause missfire CELs. Adding a lightweight pulley now or later will not affect this. So if you are not throwing a missfire CEL now, the lightweight pulley addition should not affect it. Some cars will not throw a CEL with a lightweight flywheel though so its a hit or miss thing. If you want a lightweight pulley, send me a PM with a pic of a hot chick and I can get you a source for a discounted one.
Hey Una, i did have CEL codes that were throwing after the light weight flywheel was installed. I had a local tuner reflash my car and delete the CEL for ever but last night i uploaded my first Accessport map, i hope it did not delete the tuners reflash. Unfortantaly i work at a dealership and they have a forcefield around the interwebs and i cannot look up anything involving sexy time. Maybe next time
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Old 01-25-2014, 12:23 AM   #108
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Im dealing with an issue on my 2004 STi.

My crank pulley seems to be moving forward and it has a lot of "play" to it. I found out when I was replacing my belts. My AC belt was completely off the drive pulley and the other belt is a bit aged.

We replaced them with the Gates Blue belts. Upon start up, the AC belt started jumping off the pulley again. Thats when we noticed the crank pulley was being pushed forward and a lot of the rubber thats on the inside of it was chipped off and worn.

From what I have been reading the crank pulley is just that...a pulley. People are calling it a harmonic balancer but ive read that its NOT that. Just the pulley. Did Subaru change that in 04? Because I can see the rubber inside the pulley..if that makes sense..
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Old 01-25-2014, 01:28 AM   #109
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nice write up
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Old 07-02-2015, 09:27 PM   #110
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My engineering buddy scanned a stock crank pulley and then modeled his own super light weight underdrive pulley. I asked how much power it would save and he didn't know so we did the calculations. Essentially it takes no horsepower to spin a pulley at constant speed but it does take power to accelerate it. The actual horsepower is based on a lot of things but the difference between two is all based on the moment of inertia. With 3D modeling software it gives us accurate moments of inertia. His pulley has a 22 times lower moment of inertia. WOW! So then we calculated how much power a stock pulley uses if accelerating from 2500 rpm to 6000 rpm in 3 seconds.... Less than half a horsepower. So his uses 22 times less than half a horse power so yes it makes a difference but no it's not enough to notice. You will notice a difference in reving and shifting when the engine is out of gear because that happens in a much shorter time.

I'm curious as to the claim in the initial post of a 5 to 10 horsepower gain. It doesn't seem possible. Does anyone have any dyno curves to show this along with a list of what all was changed? I haven't found any in my searching over the last couple days.
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Old 07-02-2015, 11:25 PM   #111
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They were dyno'd back in the day, but I'm sure the plots are long gone. I did see them though....promise!
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Old 06-11-2016, 09:28 AM   #112
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I read the complete topic. Power gains in the range of 5-10hp is possible. Check a dyno from a FA20 engine which adds almost 10hp:



Nowadays, even reputable engine builders sell lightweight pulleys.

Last edited by nikitopo; 06-11-2016 at 09:42 AM.
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Old 07-30-2016, 04:01 AM   #113
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So is this why all the fancy after market pulleys dont have rubber in them ?
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Old 07-30-2016, 12:41 PM   #114
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Default Harmonic Balancer

Ok, from my experience on working on LS motors, in particular to Ls2 and ls3 engines when I personally upgraded the under drive pulley (Harmonic Balancer) or in Subaru terms a (Drive Pulley) It does the same thing as a harmonic balancer but not exactly the same thing.

They both supply power to the alternator and electrics, very true. But what happened to me is when I got one of these forged name branded pulleys it basically didn't supply enough volts to the battery causing it to degrade and or die.

This is what happened to me, it sucked so bad because it happened on my ls2 and ls3 engine. Then I gave up and bought a Subaru... planning on keeping it stock as I've learnt the lesson on modding. If you have not got the money to blow on defects due to the modification's then don't do it. Like me.

But I did gain 7hp with that harmonic balancer so they do work.

But what I suggest as someone that has lost a lot of money on modding is just stick with the oem stuff. Most Subaru wrx's and Sti's are driven as a daily driver and not a race car, so just use the oem stuff as it's been tested and it's been used for what? The past 8 years in the same engine? That says a lot.

I just feel it's a safer bet. But hey, it could be fine modding the wrx's what do I know coming from the LS series engine's.
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Old 07-30-2016, 12:45 PM   #115
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If it starts to jump get a smaller belt and bring out the heat gun and blow on it. Make it really hot and then mold it to the pulley. This is what I did and it worked. Mind you it never jumped on my Ls2 6.0L GM engine after that. But it did not supply enough voltage to the battery. Healthy voltage is 14v but mine was on idle sitting at 11 and when driving sitting at 12 and when pushing it, it did not want to go over 14 which is what is the standard voltage is.
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Old 07-30-2016, 04:18 PM   #116
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Good read
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Old 08-01-2016, 10:03 PM   #117
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great work!!
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Old 12-07-2016, 11:48 PM   #118
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Ive put a grimmspeed pulley on my 03 wrx and now my rpms are high reving and it threw a p5107 idle malfunction fail safe can i reflash for the cel to disappear, could it be the throttle body or air valve. Do you think i will have to uninstall
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Old 12-08-2016, 12:24 PM   #119
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Google knows not what p5107 is, so unless you fat figered it, you have other issues. If you idle is wonky, that is likely a dirty IACV when the sticky threads in the maintenance forum can help with.
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Old 01-29-2020, 09:06 AM   #120
M3lvo
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will the lighter pulley make up a bit of rpm loss from a 4eat torque converter?
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Old 01-29-2020, 09:15 AM   #121
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Quote:
Originally Posted by M3lvo View Post
will the lighter pulley make up a bit of rpm loss from a 4eat torque converter?
Doubtful if you will notice
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