skirkland1980 Posted November 6, 2012 Share Posted November 6, 2012 Is there a formula that valve spring manufacturers use to recommend a certain valve spring pressure? I know it all depends on valve train reciprocating mass and rpm. The L28 valve spring feels a lot stiffer than a stock genI sbc valve spring and the L28 has less reciprocating mass in the valve train. Are valve spring upgrades even necessary on the L28? The sticky about valve train balancing left me with this question. Thanks Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted November 6, 2012 Share Posted November 6, 2012 Whats the operating RPM range of the two engines you are comparing? Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted November 6, 2012 Author Share Posted November 6, 2012 Whats the operating RPM range of the two engines you are comparing? I'm looking for a formula to calculate needed spring pressure that will apply to any engine with valve springs. Quote Link to comment Share on other sites More sharing options...
Leon Posted November 6, 2012 Share Posted November 6, 2012 The springs need to be stiff enough in order to not hit resonance within the bounds of your rpm range. fn = 0.5 * (k/m)0.5 Where, fn is the natural frequency k is stiffness m is mass Solve for k to get stiffness... As you can see, resonance is a function of spring stiffness (and mass). I'm not sure what you mean by "valve spring pressure". If it's pressure at the valve seat or open pressure that you're after, that can be easily calculated once stiffness is known. http://www.efunda.com/DesignStandards/springs/spring_frequency.cfm Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted November 6, 2012 Author Share Posted November 6, 2012 Thanks. This will give me something to exercise my brain. I have also heard that springs my resonate at say, 8500 rpm, and not at 9000 rpm for example so to be sure you still need spintron data. This should get me in the ballpark. Quote Link to comment Share on other sites More sharing options...
Leon Posted November 6, 2012 Share Posted November 6, 2012 Thanks. This will give me something to exercise my brain. I have also heard that springs my resonate at say, 8500 rpm, and not at 9000 rpm for example so to be sure you still need spintron data. This should get me in the ballpark. A resonant frequency is just that, one distinct frequency at which something resonates. So yes, if the resonant frequency of a certain spring coincides with 8500rpm, it will not resonate at 9000rpm, although it will experience more motion than when further away from fn. It will also resonate (although amplitude will be less) at other, "harmonic" ferquencies, i.e. 17000rpm, 25500rpm, etc. However, we don't really need to worry about this here... Quote Link to comment Share on other sites More sharing options...
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