Whenever the subject of stuffers and/or crank case volume comes up, what comes to my mind isn't so much what the effect is but rather why it does that. What it does seems reasonably well established but getting my head around the why has been elusive.
I’ll toss this out here as pure conjecture, unsure if I can put it into words comprehensible to how I picture it…
I’ve never really understood the mechanics or necessity of having any ‘extra’ crankcase volume at all, seems like there shouldn’t be any more or less movement/induction of the intake charge than what the area/volume directly under the reciprocating area of the piston creates anyway.
I can only guess that the space in the crankcase that’s in excess of piston swept volume is needed for some sort of timing/resonance/delay/storage effect?
Like that having the extra volume acts as a buffer/spring, storing energy as the downward traveling piston compresses the charge, then releasing it in a more metered fashion/curve when the upper transfers open and conversely allowing for more stored negative pressure/vacuum on the up stroke.
Picture one of those paddleboards with the ball attached by a rubber string, takes a certain rhythm to make it reciprocate smoothly, lose the rhythm and it fights itself. Make the string stronger/weaker/longer/shorter and it changes the rhythm needed...
Here the crankcase volume effects the string tension…
So... The volume of the suction/compression that the piston produces in the crankcase is a constant either way but with greater/lesser crankcase volume the pressure generated would be subsequently lower/higher, so obviously how it gets pushed out the transfers changes. I'd think one effect would be either the higher pressure burst with a shorter duration or lower overall pressure but over a longer duration, where the slower charge can take advantage of a longer time port opening due to lower rpm while the faster charge can be fully utilized with the shorter time open at higher rpm. Maybe inducing a lower but wider power band as opposed shorter peaky one, while of course realizing a small peak power gain at the higher revs. Also seems like blowdown numbers would want to change along with cc volume...