Prius Prime Acceleration

Yes, you are correct, it's a one way clutch allowing the engine and the carrier connected to it to freely rotate in one direction and lock this shaft from rotating to the opposite direction. So, as I understand it, in dual motor operation the carrier is stationary.
I do not think though that in order to spin the engine for starting it when the car is moving, MG1 should rotate in reverse to its rotation during dual motor operation. I think it is enough to slow it down (by means of excitation of stator winding) making it a generator and spinning the engine for starting it. In fact, same (slowing down) as starting the engine in non dual motor EV drive in the PiP, where MG1 is left to freely rotate.

 

Right, but of course that means no power from MG1 to the wheels during that time.

 

Yes, during this very short time, afterwards the engine gives power.

 

Yes...and MG1 reverses direction as the ICE RPM increases.

 

I don't think so, when engine is on, MG1 will reverse direction when the car is stopped to zero speed or very low speed (depending on engine RPM).

 

If you have Flash.

Toyota Prius - Power Split Device

 

OK, not to zero, when ICE collecting RPM car's speed increased as well and MG1 may eventually (but not necessarily) change direction (depending on car's speed) but this is done gradually and not being a delay on starting the ICE.

 

The issue isn't that the engine can't be started, but what the driver and passengers experience when it is while accelerating under dual motor driver. The forces from both motors is being directed to the wheels. To start the engine, some of those forces has to be redirected to the it. There is going to be a drop in the acceleration rate has that happens, and until ICE comes on line.

Under light acceleration, I don't this as being something noticed by the driver, as the system could spin MG2 faster as MG1 goes back to its hybrid functions. Under harder acceleration when there isn't that output reserve available to MG2, this redirecting of force to engine starting is likely to become perceptible to the driver. It many even feel like a car with set gears making a shift.

 

Yup. The more we find out the more similar it seems to operate to the Energi design (sans clutch). The good news is :15sec isn't horribly bad and most folks will find it adequate for all but extreme circumstances. BTDT for the past 3 years.

 

It won't be 15 sec. 0-60 with production version !
Toyota would look like fools bragging about better performance and then presenting a rather very modest acceleration performance when in EV-mode .

 

Maybe you are right, but bear in mind that more powerful motors will need more powerful battery in order to utilize their power.
PHV2 EV power is limited by the battery - 68kW while the combined max power of the motors is 76 kW.
Note also that PHV2 MG2 power was in fact downsized as compared to PHV1 - from 60 kW to 53, since with dual motors drive and 68 kW max, it can be smaller.

 

Our civic hybrid had dual cam lobes: regular lift for most conditions, higher lift under heavy acceleration, switching accomplished with hydraulics.

 

What you are describing here is not unique to the PHV2 and its dual motors EV operation, IMO the very small 'delay' will not be longer here than the small delay in PHV1 which I don't find to be frustrating in hard acceleration (although noticeable), its more like a kick-down small delay rather than shifting to higher gear.

 

Is the delay you are talking about at the start, when the accelerator is first depressed, or in the middle of the acceleration? I'm talking about it being in the middle of the acceleration event.

In the PiP, MG1 isn't doing anything beyond free spinning while in EV mode. It is essentially waiting and ready to start up the ICE. If dual motor operation is available in EV Auto and Hybrid mode of the Prime, MG1 has to stop, and the power it was contributing to accelerating cut off, first, in order to start the ICE.

 

good point. and will be smaller with worse mpg's and lower ev range. but comfy seats!

 

1. We differ here, as I stated some posts above, when the car is in EV operated and moving it is not needed to stop MG1 from revolving (and make it revolve in the opposite direction) in order to spin the engine and start it, enough is to slow it down a bit in order to achieve this, and that's in both cases of PHV1 free spinning and PHV2 spinning (same direction) as a motor.
2. We do not know if dual motors operation is used in EV Auto mode, maybe or maybe not. We do know it is in EV mode.

 

1. We agree here on how the ICE is started. The difference seems to be over how this effect the driving experience. Power diverted fromMG1 to start the ICE while in dual motor operation is more likely to be noticed than if it wasn't contributing to propelling the car.
2. We don't, but you were speculating it was earlier in this thread. This occurred to me as a possible reason for Toyota not have it.

 

You should only notice it if you were demanding more than about 52kW. If you're below that and dual motor mode was operating, MG2 should be able to take over all torque production while MG1 is getting the ICE started. If you're over that, you're going to not only lose MG1's contribution but it's going to go slightly negative as it uses some torque to acceleration the ICE.

 

Toyota says full EV acceleration may not be available (Prime owners manual pg. 87; bold underlining is mine):

■Gasoline engine operation in EV/EV auto mode Even if there is a sufficient amount of electricity remaining in the hybrid battery (traction battery) and EV driving range (→P. 199, 215, 222, 239) is being displayed on the multi-information display etc., EV driving (driving using only the electric motor) may be canceled and both gasoline engine and electric motor are used depending on the situation (EV driving will be returned to automatically after EV driving becomes possible again). EV driving may be canceled automatically in the following circumstances: ●When vehicle speed is more than approximately 84 mph (135 km/h). ●When power is needed temporarily, for example when the accelerator pedal is depressed firmly or when accelerating suddenly.* ●When the temperature of the hybrid system is high. The vehicle has been left in the sun, driven on a hill, driven at high speeds, etc. ●When the temperature of the hybrid system is low. ●When the heater is switched on when the outside temperature is below about 14°F (-10°C). ●When the windshield defogger switch is pressed. (→P. 491, 501) ●When the system determines that the gasoline engine needs to be started. The gasoline engine may also operate in circumstances other than those listed above, depending on conditions. *: When traveling in the EV auto mode only