ORIGINAL: goodvibes
the reason wide open throttle produces max efficiency is simple, that allows max air into the engine which produces max compression ratio which equates to max efficiency,
thats one of the reasons a diesel will hammer a petrol on mpg, it doesnt have a throttle so it operates at max compression ALL the time, the other reason of course is the compression ratio is about twice as high as a petrol.
mike.
A diesel is more efficient than a gasoline engine for two very specific reasons: 1. the energy density of diesel fuel is higher than petrol, and 2. Diesel fuel burns at a higher temperature than gasoline promoting a more complete burn while in the combustion chamber allowing for more energy capture by the piston. you can stop with the "diesels dont have a throttle and that is why they are more efficient" nonsense.
I do not know what you are using as your definition of compression ratio, however if you think your compression ratio is changing while you drive your car, you may have to look that one up. Compression ratio is determined by the ratio of volume in the combustion chamber when it is at TDC compared to BDC. Displacement is the difference in volume of the cylinders from TDC to BDC. While it is true that tuners use term such as Static Compression ratio and Effective Compression ratio, SCR and ECF are only used with regards to turbocharged engines where the pressure of the air entering the cylinder is greatly different than atmospheric pressure. compression ratio and Static compression do not change. while effective compression ratio can change at different throttle settings on a forced induction engine, you did not specify ECR so I am assuming that you don't know what you're talking about, I suspect everyone else assumed the same after reading your first post of misinformation on page 2. I think they were being polite by not mentioning it, as I was until you posted a second time stating the same thing.
as was also mentioned in this thread, on the BBC TV Program
Top Gear, the Stig was sent out to lap the track as fast as possible in a toyota prius, while Jeremy casually pursued in a BMW M3 at the same rate. after several laps guess what one got better MPG? hint: it was the one that was heavier, had more drag, had a bigger engine, and had self-admitting fat Jeremy driving it (everyone should be aware that the Stig is weightless) why did the BMW get better MPG? because the power of the bigger engine kept the beamer in the engines' efficient rpm range, while the Stig had to keep the revs high in the small engined toyota, which was NOT efficient.