Wouter, I'm talking efficiency of moving air. If you have 40% stale air sitting in the cylinder that has no oxygen it can't be burned. That is what I'm talking about which has a direct impact on fuel economy. Its called volumetric effiecency. If you have a cylinder that is 1 liter and you only move 60% of the spent air out of the cylinder on each exhaust stroke you're essentially wasting that displacement on the engine. The reference to 110% volumetric efficiancy means that a 1 liter cylinder ends up moving 1.1 litres of air on each intake/exhaust stroke. They do this by holding the intake and the exhaust valves open at the same time for a short period to totally wipe all the used air out of the cylinders. This is how train engines work. They use a supercharger, and a turbo charger on a two-stroke diesel with valves.

Gas engines rely on an ignition source to ingite fuel. Diesel's use pressure and heat to get combustion rolling. That's how you "knock" the energy out of diesel. That is also why turbos work so well on diesel. Take an engine that already has a compression ratio of 27:1, (vs the avg gas at 8:1), now pack a ton more air into the cyliders and it can get as high as 50:1