A work of pure genius! - Brilliant "Revetec" Engine

[pneumatic]

the RoadLoad program is for those who have not your excel nor your background, especially for the youngsters.

Yeah, it is a pity mine needs Excel. I have been learning VBA to make it a stand alone program.

Here is a plot for your discussion (I have ‘stolen’ the basic BSFC plot from internet and added the rest).

Ah, that's what we need. You can see that engine is actually at it's most efficient at medium load at about 2,500rpm. Highway cruising is a medium load for most cars (light load for really powerful cars)

You can see with the curves that Manolis drew that light loads it would be most efficient at ~1200rpm (downhill cruising).

But at higher loads like going uphill, it is most efficient operating about 3,500rpm.

My point is that if you produce better torque in a lower in the rpm range (which will lower the point in RPM when the engine labours) then you can use taller gearing which then saves fuel.

That isn't right. Can't you see your own car is the perfect example. It's peak torque is 4800rpm yet it is quite efficient operating low in the rev range. Your car has a performance engine, and it doesn't labour at low rpm. If you retuned it with a very mild cam, so you got peak torque at 3,000rpm, do you think it would make your fuel economy any better?

If an engine has enough power to pull a tall enough gear to allow it to operate at it's most efficient cruising rpm, then it has power to do it. It doesn't matter that it's peak torque is at 1000 or 8000rpm. So long as it has sufficient torque down low to pull the necessary gear ratio to get it to cruise at it's most efficient rpm.

You should be able to tune your Revetec better (generally tuning and better breathing etc), and get it to run higher in the rev range. This will move your peak torque higher and make a big improvement in horsepower. Doing this shouldn't reduce the torque it's producing low in the rev range much at all (it will reduce it a bit, but not much - not enough to cause you to need to select a lower top gear ratio).