Well, what I basically mean is that the outer electric motor is resisting the spin of the ICE and MG1, but is bleeding off torque rather than RPM - the 2 inner rings are creating more torque than needed to drive the wheels in order to reach that upper RPM needed to keep up with them.

So basically, torque needed to keep car moving forward (small) + resistance from MG2 (bleeds off) = torque created by MG1 + ICE.

If that's basically the equasion then MG1 should be in a low-rpm high-torque state, which is a very efficient state for it to be in.

 

Thank you for the pointer.
Also found following page at Graham's site...
http://prius.ecrostech.com/original/.../Overdrive.htm
And, another one is Miller's presentation...
http://www.engin.umd.umich.edu/vi/w4...Miller_W04.pdf
On the slide-41, "Negative split mode" is shown, but the MG1 is driven by battery instead of MG2(Graham's case).

I've never thought availability of these modes.
I'll try to scan my drive logs to find out these modes.

Ken@Japan

 

Thank you Ken!
On slide 4:

"The classic electro-mechanical power split transmission developed by TRW and published in a 1971 SAE paper is the basis of today’s electric power split systems. G.H. Gelb, N. A. Richardson, T.C. ****, B. Berman, “An Electromechanical Transmission for Hybrid Vehicle Powertrains,” SAE paper no. 710235, Jan. 1971"

I had read about this paper but some how failed to connect the dots. This prior art should be enough to protect Toyota from a patent infringement suit from the "electric wheel" company.

Bob Wilson

 

Bob,

How do I find out what is the most optimum RPM for the non-hybric car that I drive? Is it given in the speicifcations for the engine?

Also, if I try to maintain that RPM for the conventional vehicle at around that mark, would that help me get better FE from that car?

Regards.

Regards.

 

This is a difficult problem because we don't know enough about your other vehicle and available instrumentation. In a perfect world, you would replicate what engineers have traditionally done: add instrument and run tests.

Initially, I ran a series of benchmarks that allowed me to hold operating conditions steady and measure non-trival amounts of fuel burn. This was tank top-off over trip-meter. But to do something like what I've done, you'll need: (1) ICE rpm, (2) ICE torque, and (3) fuel consumption.

You may be able to get brake-specific fuel consumption data from the engine maker. However, these are usually done on dynometers so translating them into operational charts is a challenge.

Bob Wilson

 

My other car is Hyundai Sonata 2006 V4 with the standard instrumentation which includes the trip meter (calculates the trip MPG) and the RPM meter (tachometer ?). Currently, in the city/hwy combined driving, I am getting about 32 MPG. I am wondering whether I should "accelerate briskly" in this vehicle and come upto speed and then glide - like I do in Prius OR accelerate relatively slowly covering a little longer distance in pulse mode than covered in the other method ... In other words, what is the best way to accelerate in a traditional car - brisk/slow? I've read the jack-rabbit starts kill the MPG, which I have myself experience. But once the car gets rolling at 10 - 15 MPH, Soopahman (with his standard instrumentation in Prius) advises us to accelerate briskly (dead-band mode in the 15 -30 MPH range; no arrow to and from battery). This made me think about the optimum way to accelerate the Sonata ....



Why in the world the auto-manufacturers don't perform these tests and give the data?

What is this "brake-specific fuel consumption data" that I can get from the engine maker? Where can I find it?

Thanks for your valuable time and the info that you share with all of us!

Regards!

 

I can't seem to get a 'feeling' of which one is better from my own experience ... my wife usually drives the Prius for her drive to her University .. I get to drive it in the evenings and the weekends. During those times, I see the AVG MPG in lower 50's .. and when I drive, I push the figure in higher 50's and give the car back to my wife, who later brings down the number again .. This weekend, I pushed up the MPG to 58.6! (I was using slow accelerations this time .. not dead-banding) I am not sure whether dead-banding would have given me a better number .. It would have given a MPG number in the same range as 58.6 .. that is my guess ..

Just wanted to follow up on this test of yours .. did you see benefit in your dead-band acceleration of ICE instead of a 'gradual' acceleration ..?

 

Also, I was using the battery a lot at the lower speeds (after having learnt that using the battery at lower speeds is much better than at higher speeds).

My question is this:

1) There was this talk about not using the battery power because there are energy conversion losses involved in the process. Should we try as best as we can to avoid using the battery then? So, all pulses, even at lower speeds, should be tried to be achieved with ICE then?

2) If the battery is avoided in most cases, then when should/is the battery power used?

Thanks again!

 

Hi,

One of the harder aspect of our hybrid is realizing how often the vehicle operates, not in a steady-state condition. After awhile, you'll get it:

At speeds below 42 mph on a flat road, the vehicle will cycle between: (1) battery only, and (2) ICE recharging and power. Battery mode is great because you don't burn any fuel but it will need recharging.

The 'ICE recharging and power' mode is nice because the extra power needed to recharge the batteries puts the engine in a more fuel efficient range. If the car just tried to roll on ICE power, the setting would be so low that the Prius would get crappy City performance. This is one of the reasons why non-hybids have such wretched City performance.

Bob Wilson

 

So, in other words, it is OK for the vehicle to be operated in the battery only (EV ?) mode. Then that conflicts the statements that were made early on in the thread that "try not to use battery power as much as you can" because of the energy conversion losses - giving the idea that pulse while ICE on and then glide and repeat.

So it begged the question .. when to use the battery then? I guess, the people from this school of thought (no battery use) can make their case and we can have a healthy discussion about it ...

Regards.