For better engine efficiency, a different kind of throttle

Limiting the amount of air is the only practical way to throttle an internal combustion engine (ICE).  Unfortunately, the throttle in an ICE has long been recognised as a source of ineffciency, due to pumping losses.  A more efficient, though expensive, alternative is to control air intake using the valves.  Efficiency gains are in the range of 10%.

https://www.nytimes.com/2011/03/27/automobiles/27valve.html?_r=1

 

/ valve FIAT MultiAir microprocessors pumping loss /