Quote:
Originally Posted by projectRDM
I don't know about the SR pulley, but the whole 'harmonics' deal for KAs is complete bullshit that's been passed on for years. The rubber damper in the KA crank pulley separates the A/C portion, it's designed to reduce shock when the compressor is engaged, that's it. People for years removed that front portion and the damper and ran it in SCCA and road events before Unorthodox came out with a lightened version. I ran the UR pulley on my old car for nearly nine years, never had a seal leak, spun bearing, anything. That block is now in my new car, still fine with nearly 190k on it. UR did do a redesign because the early versions wore on the crank seal, they added a steel sleeve right after the first production run to fix it.
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Sorry Russ, but you're wrong on this one. That bonded piece of rubber and the AC ring is there because they are targeting a specific frequency and that piece provided the right spring constant and inertia to meet that frequency. IIRC, the equation is frequency = sqrt(Inertia)/k, where k is the spring constant of the rubber portion.
Now as far as engines being fine, I have no idea where the natural frequency of the stock crank is, but it might be above the stock redline, which can frequently happen with short/stiff 4 cylinder cranks. I'm still of the opinion that there are easier ways to make power with these engines that aren't as "risky" as this, because you know SOMEWHERE you are getting a HUGE amount more vibrations. Otherwise I'd think the factory wouldn't bother.
Here's an illustration of a 2nd order mechanical system, the middle one is what happens when you have a properly designed dynamic vibration absorber(i.e. a stock crank pulley):
