[jakobnev]

om my memory of the first posts in this article - from some of our best educated people - adding a turbo by itself does not guarantee increased FE. To get the benefit, you will need either a smaller engine or taller gearing, and probably both.

There was also the option of having the intake valves close later. Which is just within reach of DIY. How this helps isn't completely obvious, but to make a long story short: It increases the mean cylinder pressure on the intake stroke relative to the same during the compression stroke, hence lowering pumping losses.