My prime doesn't have much power when not in the EV mode

In the Prime (not in the regular Prius BTW) MG1 can power the wheels by locking up the sprague clutch. In this scenario MG1 and MG2 are both directly powering the car. In HV mode the sprague clutch is unlocked and the ICE can add power to MG2 to drive the wheels. In order to do this it HAS to also drive MG1 as a generator. That's what I mean by the torque split. So the amount of power sent by the ICE to the wheels is less than the total power of the ICE by approximately 1/3. The electricity generated by MG1 can either be stored in the battery or used directly by MG2.

One other note, above you state in HV mode that the engine is powering the car plus a motor. It's semantics but the ICE is never powering the car alone. It's always MG2 with the ICE in addition as needed. So at low speeds or low power requirement you can run on just MG2.

 

Why does it have to drive MG2 has a generator? If there is battery power left, why not add to the power output by also driving the wheels?

 

weirdly MG2 is the one connected to the driveline. it has to drive MG1 as a generator due to the design of the planetary gear. in order to use MG1 to help drive the wheels the ICE would be turning backwards. That's why there is a clutch in EV mode.

 

But why use MG1 to drive the wheels when MG2 is the bigger motor? I can see that you can't use MG1, MG2 and the ICE at the same time but when using the ICE, I would use MG2 instead of MG1 to help drive the wheels and I believe this is what is done. MG1 becomes a generator then if required.

 

I may have confused you. MG2 is always connected to the wheels. It is the primary driver of the car. MG1 is used as a generator AND to start the ICE in the regular Prius while in the Prime it can also drive the wheels in EV mode only. As you note, MG2 is the larger of the two motors. MG2 is also used as a generator during regenerative braking. We are on the same wavelength here.

 

Ok, that's how I understood it reading a few videos on HSD.