Is This The New PiP Transaxle?

Dual motor mode!

This means the Prius Prime has a clutch of some kind. It's not yet clear if they somehow added this as a modification to the 4th gen transaxle or if it gets the 3rd gen based "two-mode" transaxle reflected in the patent I wrote about. Based on no information whatever, I'll guess that they just stuck a one-way clutch on the planetary carrier connection to the gas engine of the 4th gen transaxle.

 

That's just done by generating extra electricity with MG1, for example, while driving. The non-plugin Prius does that routinely in order to keep the hybrid battery at a happy charge level. The same idea applies to the Prime except that the battery is a lot bigger and the idea of "charging on the fly" is presumably to fill up the battery from the engine instead of the grid so that you can drive EV-only later on if you want to be quiet or are driving in certain core areas of European cities where any use of the gas engine results in a fine for local air pollution reasons.

Doing this is less efficient than driving normally in hybrid mode because you are converting the mechanical motion of the gas engine into electricity rather than driving the wheels mechanically. It's still probably not too bad. I would guess the effective gas mileage of burning gas to store energy in the battery and then using it again later to drive in EV would still be in the mid-40 mpg range.

 

I've gotta say... I called it!

However, it's looking like the new gen 4 PHEV added one or more clutches to the gen 4 non-PHEV transaxle rather than adding clutches to an extended gen 3 transaxle.