Elon wrote:
>Yes, he is right. A 2.02 intake valve plus 15 psi boost needs about 48 lbs
>to be added when SEATED. -Elon
>
>(snip. . . ) he immediately is adding spring pressure, valve area X boost,
>for a cam change on a motor built by someone else. I'm not sure he's right
>about this. Thanks, BJ in the Bean
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I am sort of ambivalent about this. Here is why. On the intake stroke
the vlave is open so no added spring pressure is needed. On the
compression stroke, no added spring is required because the cylinder
pressure overcomes that. On the exhaust stroke, for a turbo there is
pressure in the cylinders even after the stroke is completed, so high
possibility that bo added sprng is needed then either. And of course,
on the power stroke the chamber/cyliner pressures are fairly high so no
added spring is needed then either. So while, I don't think it hurts to
add a pound or two to the spring rate, the very short times where valve
overlap might occure and need spring pressure increase is really a short
timep period. Really short. That's fora turbo car. On a supercharged
car, the idea is to remove the burbed junk as rapidly as possible and
with as littl eback pressure as you can possibly have. So the end of the
exhaust stroke might need some added rate, but the othere seems to
pretty much follow the same reasoning?
mayf
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