Quote:
Originally Posted by cRiPpLe_rOoStEr
AFAIK some very ancient engines with an IOE valvetrain had a passively-actuated intake valve which was of the conventional poppet layout, pulled open by the vacuum at the intake stroke. But I'm not sure how a reed valve could be so beneficial in a 4-stroke engine which already resorts to mechanically-driven intake valves.
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No reason not to do it this way in the old, very low rpm, engines of yore.
But at moderate to high rpms you need way more spring pressure to get the valve to close timeously.
(has way more weight/momentum than a reed)
And that pressure will stop the valve from opening when it should from the pressure difference alone...
The Reed Valve, with a very hot cam, basically gives you 'infinitely variable', valve timing, based on pressure difference...
But a reed valve cannot handle the extreme pressure and heat of the power stroke, so a normal valve is still reqd for that.
I explained more in my replies to aerohead.