2015 Frankfurt/IAA Auto Show Prius Second Showing

I believe the original source is this report from the auto show:

Bold 2016 Toyota Prius surges in to Frankfurt | Auto Express

 

VW MQB? Hole different concept, i'm afraid. Modularity vs Arquitechture...

 

Has the journalist found a motor generator in the rear axle? No photos, so hard to believe, then...

 

The Toyota EU's Frankfurt Press Release also mentioned the revised front MacPherson strut suspension!
I think this is not covered in earlier official Press Releases for the Las Vegas Reveal.

 

And I suspect the original original source is this speculative article from 2012:

New 90mpg, 4WD Toyota Prius shapes up | Auto Express

 

Frankfurt Motor Show 2015: Toyota Launches New Prius But Holds Back Details

 

This eAWD will help handling in times of poor traction, but not MPG. It's the same system used in the Highlander, RX, and NX hybrids, and they all take a 1 to 2 MPG hit with the AWD system.

The system is asymetrical; the rear is only powered at lower speeds. It's because the battery pack doesn't have a charge high enough for sustained operation, and without that charge, the rear motor will operate at a lower power in a serial mode with the ICE.

 

You're correct. I had remembered the 4WD hybrid Highlander as having slightly better mpg than the 2WD version but I went over to fueleconomy.gov and my memory was faulty. Maybe I was just impressed that adding 4WD only reduced mpg slightly compared with bigger losses with conventional mechanical 4WD.

 

A quote from the RAV4 Hybrid press release:

E-Four electric powered Hybrid AWD system

A first for Toyota vehicles in Europe, the RAV4 Hybrid AWD is equipped with a 50 kW high-voltage, high-speed rear electric motor which gives the vehicle all-wheel drive capability without the need for a central prop shaft.

Operating independently from the hybrid system’s front electric motor and driving the rear wheels alone, E-Four smoothly switches the RAV4 to all-wheel drive status on slippery road surfaces and from stationary starts, maximising traction, stability and controllability under the most demanding driving conditions.

Generating drive torque through the efficient use of power from the vehicle’s hybrid system E-Four system not only optimises all-wheel drive performance in a variety of dri-ving conditions, but also reduces energy loss, contributing to better fuel economy than that normally associated with AWD vehicles.

 

Even More on the 2016 Fourth Generation Toyota Prius - CleanMPG Forums

 

Tesla's AWD replaces one big motor with two smaller ones for their AWD. Working the two together gives the car a wider range of speeds in which it is efficient than the single motor.

Toyota just adds a motor to the rear without changing the hybrid system up front. Saying the front motor and ICE can be paired to the rear motor in a way that allows more efficient operation as seen in the Tesla, the rear motor would have to be used at speeds above 37mph. Even when full, the traction battery doesn't hold enough energy to do that for long. So the rear motor will mostly be powered by the ICE in serial mode. Such operation reduces the system's efficiency because of the conversion loses of converting the gasoline into kinetic energy into electricity, and back into kinetic at the rear motor. Those losses for the Tesla happened at the power plant, which is much more efficient than a car's engine at making electricity.

As it is an eAWD system has a lower penalty than an ICE system.

 

IMO, the rear motor is not feed only by battery but can also be feed by MG1. Remember the PSD always transfers part of the power through electricity, why not send this electricity directly to the rear motors?

The rear motors are probably "lower gear", meaning they don't work at higher speeds, but they can pull higher load from a stand still (eg. trailer).

 

It's not clear to me why 2 motors are inherently more efficient on battery operation than one motor. (Assuming wheelspin is not a factor)
Perhaps Tesla are getting better efficiency due to use of more efficient motors and the 2nd motor is a simple way to get 4WD for better traction under high acceleration. It would also facilitate using the same motor in both more and less expensive models.

 

Tesla uses squirrel cage induction motors. Such motors have relatively high constant losses when they are energized due to the reactive power demanded to magnetize the rotor. While reactive power carries no real power, the current is real and so are the I^2 * R losses that reactive current creates.

If you have a large, powerful motor, the reactive power demand to magnetize the rotor is relatively high and that creates poor efficiency at partial power. For example, if you run your 500HP motor at 20HP, you're only running at 4% of rated power and efficiency there will be much worse than it is at 500HP.

If you instead divide your 500HP motor into a 300HP rear motor and a 200HP front motor, then when you are running at 20HP you could choose to shut the 300HP motor off entirely and therefore eliminate its losses due to magnetization. Then 200HP motor would then be running at 10% of its rated power where it will likely be more efficient than a 500HP motor running at 4% of its rated power, due to lower magnetization current.

The Prius uses radial flux PM machines (well, up through gen 3 that is, we don't really know about gen 4 yet). Such machines are entirely different and don't demand magnetization current since they have permanent magnets. The losses of such machines at the low end (partial power) are often driven by eddy current losses in the magnetic steel of the stator, and are thus driven by frequency which goes directly with rotational speed. I^2 * R losses are proportionately lower at lower power levels for such machines so they tend to be *more* efficient at the lower end than at rated power except for those eddy current losses. Machine design varies quite a lot, but such machines can achieve peak efficiency in the neighborhood of 10% of rated power. So, a 60kW machine might have maximum efficiency in the 6kW range, give or take a good bit based on machine design. 6kW is probably enough to push a Prius in the 40-50mph range on flat ground at sea level.

 

I'm a German Gen. II driver and I will be there next Thursday. Maybe I can get some news and/or pics...
Any questions or requests? Perhaps I will be able to ask someone there.

Michael.


SM-G900F ?

 

The system does this.

But the FWD Highlander with the 4 cylinder can tow a trailer. Toyota is over protective of the HSD. There might be a valid reason, but I don't remember hearing one.

 

The new Rav4 hybrid has HSD and e-AWD...

 

Toyota allows the Auris hybrid to tow with its Gen. 3 Prius drive train. The only reason for not allowing the Prius to do the same would be if the tow bar isn't connected properly to the frame. My CT200h has the "plumbings" for a tow bar, but since it isn't attached to the frame, it can't tow a trailer - only a bicycle rack.