When the engine is shut off, the intake manifold cools and a slightvacuum forms as a result .
这是因为当发动机熄火时,进气歧管冷却而产生轻微的真空。
2
One does not inhale the smoke, but if one gets very good at it, one does not even have to puff: the slightvacuum created in the mouth by nose breathing will draw the finest of puffs through the stem.
The detection systemcould not press or squeeze the egg like the graders did, but what would happenif they could pull on the egg with a slight negative pressure, or vacuum?