ECVT optimal speed for mpg? At highway speeds

Probably not.......since the WHOLE vehicle is theoretically optimized for fuel economy.

 

While the car is maximizing MPG at all speeds I've found on my 2010 Prius that somewhere just above 40mph will achieve a maximum of gas mileage at a somewhat highway speed. At this speed the engine will not shut off completely and battery augments power when terrain changes. I can tell because the ECVT nearly maxes is gearing and the engine throbs just slightly (like too high of a gear in manual trans). The electric then adds the required torque to keep the engine at this lowest rpm. I find this works in fairly flat terrain and between 40-50mph. With the engine not shutting off the battery is maintained at a decent charge level.

Don't know if the newer Prius will work this way but the gen3's do. Hopefully I'll find out how the gen5 Prime does this in the next year or so.

 

The engine does have peaks at different speeds and loads where it is more efficient. The system does its best best to keep the engine at or near those peaks. That includes adjusting the eCVT ratio. You, however, have very little input in how the system does that. Controlling speed is about it.

 

No. The faster you go, the worse the fuel economy, pretty much linear. There's some flatter spots, some thresholds, but not significant. One way to to improve mpg is to take (lower speed) secondary highways, stick to the limit.

 

The eCVT will always be in the optimal gearing.

BUT, the drive modes will dictate how much electricity/gas is used when you are stomping on the gas pedal because throttle response is mapped differently in each drive mode.

 

The PWR and ECO buttons change amount of gas pedal travel required to achieve a certain throttle opening, but that's about it. I played with ECO for about the first six months, then switched it off (went back to "normal"), and found the pedal response more to my liking, easier to modulate.

 

Agree. In EV mode, the slower you go, the further you can go on the battery. Air resistance is a proportion to the square of speed I believe, therefore energy/km is proportional to speed. Idling around is extremely energy efficient in EV. When running ICE, 40 - 50 Kph is best but it can take a long, long time to get places. Very important to regen brake and coast speed off when approaching a red light etc. Friction brakes are a total waste of energy.
My Gen 4 Prime is rated at 40 km but I squeeze 62-63 out of it in the summer. 15% less in cold weather, another 15% less with winter tires and even less with the HVAC running. I take slower roads over faster ones and enjoy the view....