Max efficiency at 2500rpm?

[eicca]

If my experience on a mountain bike is any help, I believe the 1UZ has a sweet spot:

When biking, if I can get my pedaling speed at just the right spot, the natural inertia of my legs does most of the work.

I've noticed on the freeway, if I have the cruise set at 75mph which equates to 2500rpm, I can get 30mpg no problem. Anything more or less than that results in noticeably reduced fuel economy.

Is it an actual trait of engines that they have a sweet spot, where the rotating mass of the engine helps push it along and increases the efficiency?

 

[Zuffen]

My 1UZ would be doing 80MPH at 2,500rpm.

I've thought about changing the diff ratios (4X4) to up the revs at 60mph as it would save rowing the gear lever on every incline.

Fuel economy doesn't bother me but it would be nice to have torque on tap when needed.

 

[melvinmelvin]

ages back, the previous century, when I did my mechanical engineering degree
all engines in my text book had a sweet spot

the spot (or range/area rather) is quite visible if you make the right diagram

ordinary X/Y axis diagram
plotting in juice consumption, rpm, gear, hp taken out/torque taken out
make a fair number of observations and do the plotting

the sweet spot (or butter eye as we call it) will become quite visible

keep the mill running within the eye and you get a fair amount of hp/torque at reasonable rpm and reasonable juice consumption

 

[eicca]

I hope someday a manual transmission swap will only improve my highway mileage.

Because I know for a fact it will slaughter my city mileage, the way I drive...