Quote Originally Posted by pornstar
Can u elaborate what the importance of that is for a high revving NA engine?
as the pistons move down on the filling stroke the create a vacuum that draws air into the cylinder ready for the compression stroke.

the more drawing power this has the more A/F mixture that fills the cylinder and therefore the greater the combustion energy.

so vacuum is important as it determines power.

the MAP sensor compares the air pressure compared to the absolute pressure (i.e. outside air at 1 bar) and determines how much air is getting drawn into the engine and thus calculating the pulse width of the injectors to regulate the A/F ratio...

so to answer your question, it might be better to relate to a non-NA car that has a bloody big pump forcing air into the cylinders - so you see why vacuum is important for NA cars - as it is the only thing that fills the cylinders with A/F mixture...