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JonL,
Most of that description is very close to right...
except for this sentence...
"Since the exhaust system is sized to handle much more flow, the restriction of the exhaust under these conditions is small, and very little pressure is generated in the cylinder to expel the air."
The piston constitutes a Positive Displacement Pump... so the pressure generated is way above what is required to move that air out of the bore.
Your description is close enough to accept UNTIL the exhaust tubes from the other cylinders are connected together... at that point and back to the end of the exhaust .... particularly at the cranking speed you choose to use for your example... and dealing with one or two mufflers before reaching the examination point on the exhaust... how do you expect the physics you described to ' act on that entire column of air' ? You just don't have the sucking power from the slight amount that diesel engines overlap the valve opening...
HOWEVER, if you had a breach in the valve sealing when the piston starts down on the power stroke... you would have a much much larger potential effect on that column of air...
On certain functions you cite inertia or scavenging.. but then ignore it where it does not help your argument.
Why did you not address my fine testing equipment design ...and the need to differentiate between loss of pressure and actual reverse flow of air in the exhaust system all the way to the end of the exhaust ?
We do not know for sure that what we are discussing is actually what the OP is experiencing...
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