| Red__Zed |
01-19-2013 09:35 PM |
This is always a fun discussion here. There's plenty of other threads covering the topic, unfortunately they're all mostly full of folks without the requisite background parroting things they've heard, either from friends or vendors.
Quote:
Originally Posted by DEpointfive0
(Post 2120013)
I think your point doesn't hold it's weight, but...
Whatever you say brother, no one is forcing you to install one.
I have yet to see anyone scientifically and empirically show that with an aftermarket pulley your engine won't last as long.
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And you likely never will--it's not worth someone's time to prove they aren't worth it.
For me, I'd feel a lot more comfortable if the vendors published a harmonic analysis to demonstrate that their replacement was kosher.
Quote:
Originally Posted by SS_Firehawk
(Post 2120144)
That damper piece people think dampens vibration is a rubber gasket...that's it. It's made out of iron and heavy, not to magically remove non-existent super dangerous vibrations that emanate from our engine. It's the same reason they made the fluwheel a dual mass, to smooth things out, but it also saps engine response (and power). There aren't a lot of newer vehicles or engine designs that require an external damping mechanism. It's just a pulley. Even the stock piece is called a crank pulley. But alas, I'm wasting my breath to half the forum :)
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The stock pulley changes the resonance frequency of the assembly, which means it is, by definition, a harmonic absorber(damper). The important question is not what it is, but whether it matters.
wstar had some good commentary on this last time, so I won't waste my breath. you'll notice the discussion in the below post explaining that we are not discussing balancing through the use of an asymmetric pulley, but rather the manipulation of the crankshaft resonance frequency.
Quote:
Originally Posted by wstar
(Post 1341417)
Well, there's a lot of confusion on this issue about vibrations, dampening, and external vs internal balancing. I can't settle the matter for our engine, but I can clear a few things up to put the debate more on-point: Yes, our engine is "internally balanced", and that has virtually nothing to do with the debate about the pulleys.
An externally balanced engine means there's actually an asymmetrical counterweight system on the pulley, which balances against the otherwise-imbalanced crankshaft. You will definitely destroy an engine if you were to slap a random symmetrical pulley onto such an engine. Because our engine is internally balanced, there's no specific need for a balancing component on the pulley. The pulley itself is expected to have neutral balance (even weight distribution).
Even with an internally-balanced design like ours, the stock pulley includes a (neutrally-balanced) dampening ring to reduce vibrations. The debate is about whether replacing the stock pulley (poorly machined, crappy metal, with a dampener) with an aftermarket one (much lighter, machined to better tolerances, no dampener) is going to cause long term damage due to increased vibration.
On the "stock" side of the debate is the idea that the stock dampener serves to quiet important harmonic vibrations at specific RPMs, and that without it the engine will slowly tear itself apart (slowly wear out crankshaft bearings at the very least). On the "aftermarket" side of the debate is the idea that the (a) whatever vibrations the stock pulley dampens are relatively trivial and mostly about reducing engine noise heard by the user, and won't cause engine damage, and (b) the more-precisely machined aftermarket pulley is better-balanced to begin with.
There's little doubt that as you push an engine further beyond its design boundaries, you need to be more precise about balance and vibrational issues in general. The tricky question is whether our engine in basically-stock form needs that NVH ring for long-term health or not.
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I don't have the time/data/desire to crunch the numbers myself to determine how much it matters to replace the pulley with something else, nor do I have a vested interest in figuring it out. The fact that several folks have put a good number of miles down with these pulleys indicates that the pulleys probably don't change anything terribly dangerous. I do know that if I was to spend my hard-earned dollars on a part, I'd prefer to see a resonance analysis done by the manufacturer before I slapped it on my $30K+ car. |
