[mwebb]

Originally Posted by dcb

I don't think the ecoboost has a throttle, I don't know why it would need one either. The original (i.e. 50 years ago) direct injection schemes had a throttle, but I don't think it is a requirement these days. What am I missing here?

3.gasoline engines with direct injection still use throttle plates or variable lift intake valve to control air flow to the intake and by so doing
MUST have suction throttling loss es / pumping losses

Air Fuel Ratio in gasoline engines is controlled to be near 14.7 to 1 much but not all of the time in direct injection gasoline engine systems and it could NOT be controlled if air flow were to be UN controlled

if air flow is not controlled then AFR must be maintained by varying the amount of fuel to keep AFR at 14.7 to 1 , the net effect of this would be that the engine would only have one load condition
100%
wide open throttle
all the time

the throttle plate (or variable lift intake valves ala BMW) is not an option
on gasoline engines with direct injection
or
on diesel engines with direct injection