[serialk11r]

It's worth noting that the throttle is hardly the main source of inefficiency in many cases. Friction in the engine uses more power than the throttle by a long shot.

The Nissan 3.7L V6 engines and all BMW engines today use valve timing instead of the throttle to control output, but low load is still inefficient on those engines. When you only suck a little bit of air per stroke into a big engine, the fuel/air doesn't burn as hot (bad for efficiency), and the sheer amount of power it takes to overcome the friction in a big engine can be more than the power it takes to keep the car rolling down the road.

Anyways, I don't even use a vacuum gauge for pulse and glide, I just calculated the instantaneous in each gear corresponding to the max load before the engine starts running rich, and use the in-dash mpg gauge.

For example, in 6th gear, after all the arithmetic, 24mpg is 0.78 grams per revolution, 22mpg is 0.86 grams per revolution, enrichment comes on at 0.8-0.9g/rev in the cruising range, so that's where I shoot for when accelerating. In 2nd gear, it would be more like 9mpg on the dash, in 4th it is like 14mpg.