Originally Posted by olds48
Throttle plates control the engine speed by changing the density of the A/F mixture,not the amount of air supplied to the engine.
I really hope you don't believe this. If you do, you really need to step back and re-think it.
Lets change this a little bit.
You, as a human being, have a given amount of lung volume. We'll equate this to CID.
Unrestricted, you can pull 'x' amount of air (CFM) in per breath in a given amount of time (time = camshaft duration).
If you change this from unrestricted to sucking through a straw, given the same amount of time, you now pull in 'y' CID, which is a greatly reduced volume of AIR.
Density is controlled by weather, such as temperature, humidity, and barometric pressure.
Air volume is controlled by the throttle blades. The motor is unable to inject its maximum CFM based on CID due to throttle blade 'strangulation'.