European "Prime" has different EV mode names

MG2 drives the wheels, same as always. You probably mean MG1. @bwilson4web has done some research on the US Prime.

 

Coming from the land of McDonalds, it was "one wafer thin" tongue in cheek.

Bob Wilson

 

Rapid acceleration or speed can cancel EV mode in the US Prime. The top speed for EV is 84mph. With the SOC too low or the battery temperature too high, the system can decide to quit EV mode for acceleration.

The core difference between EV and EV Auto appears to be how the car delivers under high power demands. EV mode will use MG1 to supplement MG2. This uses up grid charge faster, but delivers on the EV experience. EV Auto will fire up the ICE. On paper, this means EV Auto will more likely use the ICE on a trip, but battery energy will be saved for lower speed portions. To a gentle driver, there might be a difference between the two modes during a trip though.

 

You've got it right. This is a sketch I made of the flywheel cross section:

The light-blue is a rough cross section of the flywheel. Attached to it on the engine side is the dark blue, racket teeth disk. When the engine is stopped, these angled teeth engage the slotted disk attached to the engine case. This prevents any torque from MG1 turning the crankshaft, "2ZR-FXE." MG1 has something to 'push against' so it works in parallel with MG2 through the "P610" gears. This means MG1 and MG2 work as if they were a single motor when in EV mode.

By changing the torque direction of MG1, the engine starts spinning and begins running. Then MG1 becomes the counter torque needed to get power out of the engine and through the transaxle, P610. It becomes an ordinary, Prius hybrid, with an eCVT.

Bob Wilson

 

This is one area where we need some owner metrics as the difference between "EV Auto" and "HV" modes seem ill defined:

• HV - definitely shows variation in SOC but around a 'set point' when it is first engaged.
• EV Auto - appears to let the SOC bleed down over time but at a slower rate than "EV" only mode.

I don't have enough seat-time in "EV Auto" to know what the control laws are doing. Perhaps the April SAE papers will have more details. Now that I have the SOC as a percentage, I may try some intermediate, 30-40 mile trips in both "HV" and "EV Auto" to measure the effect.

Bob Wilson

 

Nice explanation of the ratchet system, Bob. First time I've seen one I can understand.

 

In the Netherlands we had EV-City in the PIP. When in EV-City mode the ICE only starts when you floor it. It also cancels the DRCC, why that is I don't know.
The Prime in the Netherlands is called the Prius PHV and also seems to have a EV-City button and NO EV-auto. The function in the PHV of the EV-City button is to half the electric power to save energy from the battery. When you floor it the ICE will come on to supply max. power. The idea is to save power so you have more kilometers electric range in the city. Downside is that when you drive on the highway it will deplete your battery rapidly, for that you would like to have EV-auto. I'm having a discussing with the Toyota importing company in the Netherlands about that. My PHV is scheduled for delivery at the and of march......

 

On the understanding that I don't know what I'm talking about, could the dropping of DRCC when activating EV-City mode be to conserve the power used for the radar, etc?

 

I'd say it is about liabilities. Toyota expects EV City to be used in a city, where there are plenty of stops, and traffic can be heavy. They don't want to be held accountable if someone uses DRCC in those conditions and gets into trouble.

I remember when basic cruise control couldn't be used at speeds under 35mph to 25mph.

EV Auto doesn't work any differently than EV City by the sounds of it. There was some posts here where people never had the ICE come on while in EV Auto. With EV mode capable of a max speed of 84mph, Toyota would have to severely reduce the ICE on thresholds for EV Auto. This is all software changes though, so Toyota could easily do so for EV City.

 

@bwilson4web is his tag, so this should ping him 4 U. LOL

 

There is nothing to learn from "HV" and "EV" mode. We have a chart of mph vs MPG for "HV" and "EV" simply pegs the trip meter at 199.9 MPG. It is only "EV Auto" that is new to me which is described as a blended mode of the other too.

My ordinary driving mode is ECO using dynamic cruise control. Developed early in 10 years of Prius driving, I typically cut through the neighborhood, 25 mph, to minimize engine warm-up cost, before using a light to turn onto a cross town, 50 mph, street:


The first step is to practice. Since my historical data was a Toyota Echo, I'll start with that route and speed profile for a week. The only problem is my office was changed four years ago and there are two approaches: (1) drive past the original office, or (2) take an earlier exit that cuts out about at least a mile. Like it says in the package, "Some assembly is required."

UPDATE: First test, 10.6 miles, the engine did come on but the trip meter still shows 199.9 MPG.

Bob Wilson

 

I don't think they are different at all. Just that the manual is horribly written.

EV mode is EV mode, and EV Auto is EV City. Things like top speed for ICE on could be tweaked for EV City, but the basics will be the same.

If EV Auto is about preserving EV range by using the ICE well electric alone becomes inefficient, then it won't have dual motor use, and we know the ICE comes on under heavy acceleration already.

 

I thought dual motor only occurs during high demand.