Hey, let me try to show an example how air could be moved and zero vacuum be created…

Ok, in order for a cylinder to fill with air, it merely has to have the piston move out of the way, and atmospheric pressure maintains the volume with air.
Take the top off a canister, and it is full of air. No vacuum needed. Push the bottom of the canister, and the air pushed out… move the bottom back, and the air stays with it, refilling the canister…
You would only produce a partial vacuum if the bottom moved and the top had a restriction, so the atmosphere couldn’t rush in immediately… I would say that intake valves qualify as restrictions… as do intake ports… both are smaller than the cylinder… ergo, restrictive. So, INSIDE the cylinder, a partial vacuum exists… the intake runner in the head would be an airflow plenum, and smaller than the piston cylinder volume, so also a restriction, again, partial vacuum…

On a gasoline engine, the intake valves overlap in time with the piston drop, maintaining a constant vacuum in the intake behind the throttle plate…

A traditional Diesel engine has different valve timing, and opens as the piston begins dropping… so, the vacuum is far less than in a gasoline engine.

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Are you talking about otto cycle, atkinson cycle or miller cycle? What about BMW's Valvetronic or Fiat's MultiAir that don't use a throttle but widely vary intake timing/duration to throttle the airflow into the cylinder?





Except with Mercedes OM engines, where the valve overlap and intake opening timing is different between turbo and non-turbo, and even year to year.


Blanket statements do not fit well in discussions.

Venturi effect