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02-06-2003, 03:21 AM | #1 |
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lightweight crank pulley with harmonic dampner, stock size
I don't know if I am posting this in the proper place but I guese I'll find out.
I wondered of anyone can point me towards a lightweight crank pulley that incorporates harmonic dampening into it's design. I want the benifits of the lightweight crank pulley without the fear of damaging any thing. I looked through a good deal of product reviews but if any thing was mentioned about this I must have missed it. I want to find one that is lightened but is also NOT and underdrive style pulley. Thanks
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02-06-2003, 06:43 AM | #2 |
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not yet
So far I have not been able to locate one. I have been looking for one for over a year.
Near as I can determine no vendor makes one for our cars. Larry |
02-06-2003, 08:23 AM | #3 |
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Just get a lightweight flywheel. It will have a bigger effect.
Kevin |
02-06-2003, 08:38 AM | #4 |
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So far I have read all the discussions on the crank pulley issue.
Wouldn't a lightweight harmonic dampener be an oxymoron? I came away from all that reading with the understanding that the stock crank pulley tames the crank's vibrations through a combination of weight and an intermediary rubber ring between the hub and the belt drive ring. Looks to me like the best solution would be to make a dampener out of something with a greater density than cast iron so the hub could be smaller, but weigh the same. Tungsten is about 2.5 times denser than iron and is not horribly expensive at $25 per pound in powdered form; most all tungsten shapes are done through powder metallurgy. The outer ring could still be stainless or aluminum to cut down the cost. Then you would need to have the two pieces vulcanized together. Finally the whole assembly would need to be balanced. You'd probably end up with a $1500 dampener when all was said and done. But you'd have your 5 HP! Mitch |
02-06-2003, 07:28 PM | #5 |
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1 thing for sure is, they do not make a lightweight pulley with the rubber insert because the harmonic-balancer effect is lost due to the weight difference. Is pointless. Therefore I think that a rubberless pulley and a LW with a rubber insert will both cause the same damage (assuming there is any long term damage) if any.
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02-06-2003, 08:01 PM | #6 |
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tuned systems
To a degree your right. The rubber bonded ring type of damper is a tuned system, like a pendulum it depends on both the mass of the mass ring, and its distance from the rotational center ( and to some extent the stiffness of the rubber ring) to determine which frequency it has maximum damping effect. You can replace weight on the ring, by changing the spring effect of the rubber, and its distance from the center.
As all things in manufacturing the stock design most certainly is designed for most cost effective manufacture. The other thing to keep in mind is there are other designs of dampers that are not tuned systems and damp the most severe motion regardless of frequency, so there should be options for other designs if a vendor wanted to. I continue to research the issue. Larry |
02-07-2003, 02:34 PM | #7 |
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1 thing I wonder, even though I am not really comparing apples to apples. WHat would engine longetivity be like with both, a lighweight flywheel and the lighweight pulleys.
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02-07-2003, 02:46 PM | #8 | |
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My understanding is that with a boxer engine, the pulley is just that, and not used for balancing at all. Some people experience more perceived knock counts by the engine due to a lack of it, but the problem seems pretty isolated. If you do a search, this has been discussed extensively.
Quote:
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02-08-2003, 01:57 AM | #9 |
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Viscous silicone fluid filled systems work really well, haven’t seen one for a rex/suby. Coming out with a light weight version of a pulley is simple, however, the torsion’al vibration characteristics of a particular engine are extremely dynamic; R&D would be prohibitive to develop one for the relatively small Subaru 2.0 aftermarket. Engines that have been around for a long time and see extensive use on racing and hobby fronts get the development done. If you want a lighter, better tuned high performance piece for your 350 you are good ta' go, otherwise its a rough battle finding one that does what it is intended to.
SLR- edit (sp)- oh my lanta! its filled, not filed... Sry! Last edited by SuicidalLabRat; 02-08-2003 at 05:09 PM. |
02-08-2003, 09:03 AM | #10 | |
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The GFB pulleys seem pretty nice, and I've read alot about them working very well without any problems. Here is a quote from another forum, from the owner of GFB (I think)....
Quote:
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02-08-2003, 11:22 AM | #11 |
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hotrod, one thing to consider doing... go ask the other countries (in their forums).
I'd have to think that there are at least a handful of people in Australia, etc... who have had lightened crank pulleys for 4+ years on the earlier WRXes. |
02-08-2003, 09:30 PM | #12 |
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experience in other countries
Jblaine:
Good point, I just don't spend any time on the other boards so have not done that. It is in any case for my interests a moot point. The quote above in screaminfast's post pretty well covers the power making process. I choose not to go to the solid pullies because I consider it to not be good engineering practice. I know full well a lot of folks have done it for a long time without having any problems that _they_ attribute to the light pullies. From a historical perspective there is ample evidence that internal combustion engines need dampning and all sorts of odd problems crop up without it. Many that the average person would never associate with the pullies. Engineers have learned these lessons over and over again -- I see no need to participate in another experiment. More importantly, to be rules compliant with NHRA rules you need one if you run faster than an 11 sec ET. Plain and simple without an SFI approved damper you cannot legally compete once you get into the 10's, for that reason alone we need to find a means to aquire them, because we have a bunch of folks that will be breaking into the 10's this next season. Larry |
02-09-2003, 09:13 PM | #13 |
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details
1) Yes -- But --- It has no harmonic balancer, it is however a harmonic damper.
The term harmonic balancer has (unfortunately) become a generic term for harmonic damping. The stock WRX crank pully is a two part construction with an outer mass ring bonded to the hub by a strip of rubber. No matter what you call it it reduces torsional harmonics on the engine, and your correct it has absolutely nothing to do with the crankshaft rotational balance. 2) No -- The purpose of a true harmonic balancer is to economically achieve rotational balance on some engines that cannot conviently put enough weight on the crank shaft. These are "externally balanced" engines, by putting some of the balance weight on the crank shaft pulley assy. 3) Just because some vw's and the s2000 have no harmonic balance is irrelevent to the discussion. We have several documented cases where high power subaru's have harmonic related problems when they run solid light weight pulleys. Torsional harmonics increase with rpm and hp. What works on a stock engine may not work in a modified engine. 4) see 1 above 5) Only a design engineer at subaru can make that statement with any credibility 6) wrong, proven false on several cars. Larry Last edited by hotrod; 02-09-2003 at 09:18 PM. |
02-09-2003, 11:12 PM | #14 |
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After a quick review of about 5 threads on harmonic dampers, and light weight pullies;
Users who have reported problems that they believe are traceable to pulleys include at least the following folks on this board: goodfinder jaygold azscoobie torch jmott cobb tuning sophocles procrustes mjspiers http://forums.nasioc.com/forums/show...hreadid=126439 http://forums.nasioc.com/forums/show...hreadid=281124 http://forums.nasioc.com/forums/show...hreadid=132648 Larry Last edited by hotrod; 02-09-2003 at 11:18 PM. |
02-09-2003, 11:42 PM | #15 |
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Yeah right
Tell you what, when you have about 40 years of engine building experience under your belt, come back and we can talk about this. Larry |
02-10-2003, 09:29 AM | #16 |
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I think Precentor has shown up at a gunfight carrying a knife.
Mitch |
02-10-2003, 09:39 AM | #17 |
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I'm not wearing a belt.....I'm sitting here in my boxers....I think all my experience fell off with my pants....
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02-10-2003, 10:34 AM | #18 |
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it was my understnding that the proublem with lightened pullies had to do with the magnetic properties of aluminum .. not with the absence of the dampener
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02-10-2003, 10:40 AM | #19 |
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You're not serious are you?
Mitch |
02-10-2003, 12:18 PM | #20 |
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Have been driving for months with Perrin lightened crank pulley without any adverse effects. Stock one is extremely heavy IMO
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02-10-2003, 06:47 PM | #21 | |||||||
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The world is round
My my where to start ---
Okay Brad, it was kind of a busy night at the data center last night so didn't really have time to follow up on this. I suspect the reason you're pushing this issue is because your running your business tbracing.com on the private for sale classifieds here on this board, and like clubwrx where you at least registred as a vendor, you sell a lot of these things. Well I can understand a sales guy defending his market share. But your not doing a thing for the credibility of your business with this ill concieved move. Quote:
Quote:
If you'd done just a bit of research you'd know that : a) that little notch you refer to --- its called a key way to folks who work in the mechanical trades. b) The folks you say probably couldn't properly install the pulley happen to include: 1) one of the top subaru tuning shops in the US -- Cobbs tuning 2) AZScoobie the owner of one of the 3 fastest street drive WRX's in the US -- yes he does his own work 3) Goodfinder the owner of a wrx that is good enough to win major car shows and be featured in magazines. just to name three. I won't quote any threads I'll let you go find this stuff out your self. Quote:
Quote:
Of course the other things that influenced my judgement on you car skills might have also included. Quote:
Quote:
Now lets get to the issue of the balancer itself. Quote:
If you'd bothered to crawl under your car you'd see that the belts pass directly around the outside of the mass ring on the crank shaft pully. That is the reason Subaru does not call it an assembly. It is held on with a single bolt in the snout of the crank shaft. If you will turn to page ME(DOHC TURBO)-46 in the subaru service manual section 3, perhaps you can point out which illustration on that page shows how you remove the pully grooves from the crank shaft pulley. I know the removal instructions listed by Subaru do not give any indication that there is any way to separate the two. Of course with your vast experience in auto mechanics perhaps you have a new and novel way of doing things. Larry |
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02-10-2003, 07:55 PM | #22 |
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*beeeep* *beeeeep*
"Popcorns done!" *pulls up chair for amusing thread* "this is getting good, keep going!" |
02-10-2003, 08:43 PM | #23 |
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Precentor, I don't know what you are looking at, but it can't be the harmonic dampener/crankshaft pulley. Take a look at these pics:
That is what one looks like. The first picture is what the engine sees looking out. The shiny part in the middle where the keyway is cut (look for the blue dot) fits over the snout of the crankshaft where there is a mating key that keeps the dampener from rotating. Notice there are 3 distinct parts of this dampener: the inner hub (we just talked about that), a rubber ring (the middle circular piece) and an outer ring (where the drive belts ride). It is all one piece as the inner hub and outer ring are bonded together by the rubber ring. The dampener is then held to the crankshaft by a large bolt and washer. The bolt threads into the end of the crankshaft. That's all there is to it. I think Larry has been reasonable to this point. You owe him an apology. Learn from your elders. These guys have forgotten more about cars than you will ever know. Mitch |
02-10-2003, 09:28 PM | #24 |
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apology received
Just got pm apology from Precentor
Thanks You may now continue with the thread |
02-10-2003, 10:20 PM | #25 | |
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Quote:
Here's a suggestion: if you can't find a proper part from Prodrive, Cobb, or STi, then probably this is not a cost effective way of making more power on this engine. These guys have the capabilities to make just about any part they want, after all, and they've been at it quite a while. Just because the Honda guys do it doesn't mean it is the best answer for every car. There was another guy in the thread somewhere talking about NHRA's rules for going into the 10's. Why not just run the stock damper? Surely the rules don't state that an engine which is internally balanced must have a balancer, and the original pulley IS a damper. Sure, it'll cost you five or ten horsepower and your engine won't look as neat. You know what? If you're in the tens in a WRX, nobody will make fun of your crank pulley. That's a fairly sure bet. |
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