Here's the graphs for FORD.



4 examples are given. Of course, there are nearly infinite possibilites between the lines.

At ICE speed of 1000 RPM for example, the generator will be between 4000 and -12,000 RPM.

At ICE speed of 4000 RPM, for example, the generator will be between 15,000 and -1000 RPM.

Since the Max. speed allowed is 12,500 with brief excursions to 13,000, you can now say it is not allowed to have the ICE at 4000 RPM with the car standing still.

Normally, the soonest you will see engine speed of 4000 RPM will be @ 17 miles per hour.
The Ford can have 3000 RPM at a stop. That does not mean it does, but it can.

Notice the "best" line, (least extreeme) orange line, in the center, is ICE 2000 RPM.
What RPM ( or close ) does this car run at most often????