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Question on valve spring

  1. Sep 23, 2007 #1
    Hi guys, i am doing some calculations on the valve spring of a 4 stroke, 4 cylinder motor vehicle engine.

    To my understanding, valve bounce will occur once the valve spring is operated at a speed over their natural frequency (which i calculated to be 5500 rev/min). If i were to push the engine speed to 8000 rpm, does it mean that the valve spring won't 'bounce' since the camshaft only runs at half the engine speed? But if that was the case, why do most vehicle have red lines at 6500rpm on the rev counter? Is it really neccessary to have such large safety factor?

  2. jcsd
  3. Sep 23, 2007 #2


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    Gold Member

    Valve float is not by any means the only factor determining rpm limits. You get into things like rod stretch, valve closing impact, ring wear, cam lobe wear, and the ever-popular exploding flywheel that cuts your legs off.
  4. Sep 25, 2007 #3
    Also I would think that things like volumetric efficiency, valve timing and ignition timing will do the limiting for you.
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