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    Thread: Someone Prove It

    1. Banned SVTDanny's Avatar
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      10-02-2012 01:36 PM #26
      Quote Originally Posted by Yak Meat View Post
      I greatly appreciate you sharing your personal experience as well as noting others you have heard about.

      The purpose is exactly as you said, I am trying to dispel an 'urban legend'. It seems many tuner for many different cars and makes have after market light weight pulleys available for cars. And on most forums I have seen there is the typical split of people who have them and like them or don't have them and throw physics around trying to prove their negative effects without having any concrete proof other than formulas, theories, and forum physics. So in an effort to quiet these rumors. theories, and everything surrounding the pulleys, I am trying to build a thread with examples of both good and bad or at least some proof one way or another of their effects.

      This is also why I am limiting the examples to bolt-ons at most. I have no doubt that it is on the rare side for someone to mess up putting an engine back together after a rebuild with new internals, however, there is always that possibility and the variables greatly increase with built motors being allowed as examples. A Motor that has never been opened up but has pulleys and has failed would be ideal.
      The internals of the engine produce frequencies during operation. The harmonic balancer is designed to do just that - balance the harmonics. If you remove it, then you have a crankshaft spinning to 7,000 RPMs without being in balance. Over time this will cause bolts to back out, trash bearings, or worse.

      There is no "myth" here. If it was a "myth," then OEM's wouldn't spend the time or money to create a harmonic balancer on every engine that they put out.

    2. Member Yak Meat's Avatar
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      10-02-2012 02:09 PM #27
      The last three posts are good and I understand them execpt for 2 parts.

      1) I want proof... Show me a motor that has run pulleys for 100-150k miles and has suffered a failure related to what you speak about and i will believe it. Sure the harmonics are there but maybe they are not enough to make a difference.

      2) You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong. 2) You mentioned lightening the internals - wouldn't that change the harmonics and therefore cause the current damper to be incorrectly weighted? So we can change the weight of internals and there is no issue, but when you change the pulley there is?

      Forum physics: applying physics to only the areas you are concerned with and screaming about the negative effects without taking into account the entire system or how great the affects are.

      You just did it right there... Internals lightened = fine, Pulley lightened - not fine...

      Beyond this, because we are getting away from what I want, I am not looking at a modified engine internals wise... I want a closed engine with bolt-ons at most that blew up from a pulley being added/lightened/changed.

      And if no one can prove it then the response to the age old question of "Should I get pulleys" is now:

      If you do not plan on going BT or Adding FI there is little to no conclusive evidence that says a lightened pulley will damage your motor. However, if you do plan on going FI or adding a BT, the harmonics of the motor become more important and while I have no examples off hand, everything is getting stressed that much more, therefore, you have a greater chance of having those harmonics getting thrown further out of whack. That combined with the significant increase in stress across the engine system could result in a failure.

      ~~~~

      Once again guys, PROVE IT! I dont see any hard examples of a bolt-on motor being destroyed because of a pulley. Hell, Ive seen 2 stories of BT and added FI guys with lightened pulleys having failures related to the pulley, and one posted above. Another was the Mk5 R32, i tracked the thread down and read it some.
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    3. Banned SVTDanny's Avatar
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      10-02-2012 02:18 PM #28
      Quote Originally Posted by Yak Meat View Post
      You just did it right there... Internals lightened = fine, Pulley lightened - not fine...

      Internals are balanced. Lightened pulleys are not weighted specifically to balance out harmonics.

      I doubt you'll find a motor that has been destroyed, and the failure was traced back specifically to lightweight pulleys. What is indisputable however, is that a lightweight, non-harmonic balancing crank pulley will cause excess wear over the stock unit.

    4. Geriatric Member AKADriver's Avatar
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      10-02-2012 02:57 PM #29
      Quote Originally Posted by Yak Meat View Post
      1) I want proof... Show me a motor that has run pulleys for 100-150k miles and has suffered a failure related to what you speak about and i will believe it. Sure the harmonics are there but maybe they are not enough to make a difference.
      Again, you're searching for an anecdote when we've given you science. That's backwards reasoning.

      You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong.
      Grassroots Motorsports has run the experiment a few times, most recently in 2011 using their STR Miata. They saw no appreciable lap time change between wheel weights - and that's a best-case scenario, where the car is both accelerating and cornering, and on a lightweight car without much power. I have seen dyno tests showing +/-5hp or so from a wheel change, but like I said, when you're making substantial engine mods that gets lost in the noise.

      For a race engine that gets frequent rebuilds but where every thousandth of a second counts, driveline mass is more critical and omitting the harmonic damper might be worth a look.

      You mentioned lightening the internals - wouldn't that change the harmonics and therefore cause the current damper to be incorrectly weighted?
      Possibly, if the damper also acts as a balancer, though engine builders will generally seek to balance the new rotating assembly the way the factory designed, even if the new parts have different masses.

      There are two different functions you're conflating here. A harmonic balancer has an offset weight to balance the rotating assembly. Not all cars have this on the crank pulley; some are internally balanced, and some use the flywheel assembly for this. A harmonic damper has an elastomer band separating the hub from the heavy outer rim, allowing it to vibrate out of phase with the crankshaft, which in turn damps the crankshaft vibration. Any production engine in the modern era has a damper. The tuning of the damper isn't as exacting as the balancer.

      So we can change the weight of internals and there is no issue, but when you change the pulley there is?
      It's only not an issue to change the weights of the internals if they are then correctly balanced. It's only not an issue to change a pulley if the pulley is also correctly balanced and the damper is left in place. There are aftermarket pulleys that contain dampers.

      Forum physics: applying physics to only the areas you are concerned with and screaming about the negative effects without taking into account the entire system or how great the affects are.
      You're not even understanding the depth of the problem if you think anything we're saying is as simple as "Internals lightened = fine, Pulley lightened - not fine".

      And if no one can prove it then the response to the age old question of "Should I get pulleys" is now:
      You're not an authority on this. Neither am I. You're not only grasping for anecdotes in the face of real information, though, but you're using the lack of those anecdotes to prove a negative. There is "conclusive evidence" that says a missing harmonic damper or balancer may cause long-term damage. Some engines are externally balanced and require a balancer. All crankshafts vibrate and tis vibration can be damped with a damper. There are no anecdotes which provide a tidy "I installed a pulley and blew my stock engine" story, sorry.
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    5. Member Yak Meat's Avatar
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      10-02-2012 03:19 PM #30
      I am merely playing the other side of the argument. And still no one has provided proof.

      I am trying to fully understand the physics behind everything and I did mix up the damper verse the balancing aspect. My mistake.

      I am not disputing the physics or science behind it. It is completely sound and I stand behind it. Hell I am the first person to shout science at people with regards to almost anything. However, as this discussion (thank god it has remained a discussion and not turned into an argument) has evolved the only thing I am stuck on is the fact that there is no evidence, hard proof, that pulleys on a stock-ish motor will cause issues.

      Yes, the science is sound, and definitely true, my argument isn't with the science, but my point is that, on our motors with only bolt-ons (1.8ts, VR6s, ect) the harmonics are not affected enough to cause issues. The magnitude of the affect harmonics and imbalance is not enough to cause failure within the foreseeable lifetime of the motor. Once you start adding the additional stresses of FI or BT, I can see my position being thrown out the window, however, until someone shows me evidence, not just science that a stock-ish motor has had issues, I will not support the pulley bashing.

      Guys, just to clarify, I started this thread so we can post it when someone asks about pulleys and have conclusive information regarding the side effects of the pulleys. I am just playing the advocate role. (I will never put a lightened crank pulley on as I track my cars and they see a lot of additional stresses.)
      Last edited by Yak Meat; 10-02-2012 at 03:22 PM.
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    6. Senior Member PowerDubs's Avatar
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      10-02-2012 04:10 PM #31
      I'd say manufacturers install them more for NVH than for engine longevity purposes.
      -Josh
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    7. 10-02-2012 08:54 PM #32
      Quote Originally Posted by Yak Meat View Post
      2) You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong.
      No, they don't make a big enough difference.

      http://www.carcraft.com/projectbuild...ls_comparison/

      In this article they dropped 82lbs of unsprung weight and the car only gained 1/10th
      "The Sebring is an extraordinary car. Ugly to behold and hateful to drive, it is not cheap, elegant, comfortable, practical, prestigious, clever, economical, luxurious, well designed, well thought out or, if the rental car I drove in America this year is anything to go by, especially well made either." - Jeremy Clarkson

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      10-02-2012 09:08 PM #33
      so i have lightweight pulleys on my car, its a 2004 gti vr6. ive had them on for probably close to 100,000 miles now. never had a problem. but, there is one thing, the crank pulley i took off, was just that, a pulley. there is no external harmonic balancer to be found on my motor. i think the problem are people removing the balancer for a pulley. there is a reason those balancers are on there. do u think car companies would be putting them on for decades if there wasn't a reason?

    9. Member drecian's Avatar
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      10-03-2012 11:30 AM #34
      Quote Originally Posted by Yak Meat View Post
      Once again guys, PROVE IT! I dont see any hard examples of a bolt-on motor being destroyed because of a pulley.
      I don't really understand what kind of engine failure can be proven beyond a doubt to be caused SOLELY by the pulley. The case with the flywheel bolts backing out could be due to many other causes. Two cases could still be coincedental with difference causes.

      Its like saying that lighter wheels reduce wear on brake components. Everyone understands the science behind rotating mass and inertia, but outside of controlled experiments, too many other uncontrolled factors are in play.

      My $0.02
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      10-03-2012 11:32 AM #35
      Quote Originally Posted by karl_1052 View Post
      No, they don't make a big enough difference.

      http://www.carcraft.com/projectbuild...ls_comparison/

      In this article they dropped 82lbs of unsprung weight and the car only gained 1/10th
      Go outside and run down the street. Rest up until you are ready to do it again then try it with 20 lb lead boots on. See where I am going with this?
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    11. 10-03-2012 04:07 PM #36
      Quote Originally Posted by MJZman View Post
      Go outside and run down the street. Rest up until you are ready to do it again then try it with 20 lb lead boots on. See where I am going with this?
      Read the actual test results I posted, not anecdotal stories.
      "The Sebring is an extraordinary car. Ugly to behold and hateful to drive, it is not cheap, elegant, comfortable, practical, prestigious, clever, economical, luxurious, well designed, well thought out or, if the rental car I drove in America this year is anything to go by, especially well made either." - Jeremy Clarkson

    12. Geriatric Member AKADriver's Avatar
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      10-03-2012 04:13 PM #37
      Quote Originally Posted by MJZman View Post
      Go outside and run down the street. Rest up until you are ready to do it again then try it with 20 lb lead boots on. See where I am going with this?
      Thing is, light vs. heavy wheels is more like running in cross-trainers instead of specialized running shoes, not the lead boot extreme. There's some added weight and inefficiency, but it's at the margins, not a major difference.

      I switched from 19 to 12 pound wheels on my car and there was a difference in the way the car felt but I doubt there was a real change in performance.
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    13. Geriatric Member AKADriver's Avatar
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      10-03-2012 04:24 PM #38
      Quote Originally Posted by 04VR View Post
      so i have lightweight pulleys on my car, its a 2004 gti vr6. ive had them on for probably close to 100,000 miles now. never had a problem. but, there is one thing, the crank pulley i took off, was just that, a pulley. there is no external harmonic balancer to be found on my motor. i think the problem are people removing the balancer for a pulley. there is a reason those balancers are on there. do u think car companies would be putting them on for decades if there wasn't a reason?
      Right, on plenty of cars the pulley is just a pulley.

      Interestingly, even though Subarus have a pulley that does have a damper built into it, Grimmspeed has this quote from Subaru of America on their website:

      Quote Originally Posted by SoA
      Thank you for your patience as I checked with our Technical Services Department regarding your message below. They advised that the crank pulley is a pulley and nothing else. It is not used as a harmonic damper/balancer. Thanks for the opportunity to be of assistance. If you need any future assistance, please feel free to contact us again."

      Best wishes, John J. Mergen

      Customer Service Department Subaru of America, Inc.
      I still wouldn't buy one, as it's $130 that I don't think would actually do anything noticeable on a stock car in a double-blind test.

      Oddly enough, Subaru published an SAE whitepaper about the EJ22T engine in 1989 which specifically calls out the pulley as a double mass harmonic balancer intended to disperse the torsional vibration of the crankshaft up to 7500rpm.
      Last edited by AKADriver; 10-03-2012 at 04:29 PM.
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    14. Member The A1 and A2 German's Avatar
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      10-03-2012 04:31 PM #39
      Hope for TCL?

      An ~informational thread with proper content not turning into a high school drama.....almost feels like TCL 1.0

      Carry on .
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      10-03-2012 04:33 PM #40
      Quote Originally Posted by MJZman View Post
      Go outside and run down the street. Rest up until you are ready to do it again then try it with 20 lb lead boots on. See where I am going with this?
      Hmm. I went from the stock 17" wheels on my Mustang to 20s. No noticeable difference in any performance factor other than having better grip from stickier tires.

      There. My anecdotal experiment cancels yours.
      I love cars, but the problem is they are like schroedinger's hobby. They're always in a quantum superstate of being both awesome and a huge waste of time and money... until observation momentarily forces them into one state or another.

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      10-03-2012 04:46 PM #41
      Spun bearings in the SVT Contour Duratec engine are believed to be because of the crank pulley. A lot of guys install the one from the ST200 in europe. It's a heavier dual mass dampner. I know one I owned had one installed and never had any engine issues. Sold it with 160k on it. It's ok to do power steering and alternator pulleys but I'd never change the main crank pulley.

      Here's a pic comparing the 2. Stock is on right obviously. Ford must have redesigned this for a reason.
      Last edited by todras; 10-03-2012 at 04:54 PM.

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      10-03-2012 06:58 PM #42
      Quote Originally Posted by karl_1052 View Post
      No, they don't make a big enough difference.

      http://www.carcraft.com/projectbuild...ls_comparison/

      In this article they dropped 82lbs of unsprung weight and the car only gained 1/10th
      If anything, that article proves that it is a noticeable difference, IMO. Going from 12.14 to 12.03 is a pretty good gain from simply swapping wheels. Why in the world to you think that F1 teams, MotoGP, and LM cars use very lightweight magnesium wheels? It surely isn't for bragging rights.
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    18. Senior Member PowerDubs's Avatar
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      10-03-2012 07:27 PM #43
      Not to mention that at low 12's, a tenth is a lot.

      Now if we were talking going from 16.2 to 16.1, that would be different. The wind resistance alone at those cars traps would be hugely different.
      -Josh
      Current VAG collection- 08 TT coupe 3.2 MT | 06 Phaeton 4-seater 6.0 W12 | 04 VW R32 | 03 GTI VR6 - all of them 24v VR6 based.
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