[unclehan]

Hi, I wonder if there are any situations where the Prius is powered solely by the gas engine?

Are the batteries only used in acceleration and hills? What about regular 50 mph cruising? Does the motor and engine share the load or just the engine/motor? How about high speed cruising?

Any place where I can get a comprehensive idea of how the powertrain works?

Thanks

 

[MUGlover]

Hybrid Synergy Drive - Shared Power

The most detailed explanation of the Prius powertrain (that I could stand to read) can be found in the Knowledge Base section of PriusChat.com in an article called "The 5 stages of HSD." Of course, the 5 stages are called S1, S2, S3a, S3b, and S4. Hope this helps.

Once in the Knowledge Base, select FAQs, and the article is currently on Page 2 of 3. The link below will work; I just don't know how to clean it up so the linked text just says "here."

http://priuschat.com/forums/kb.php?mode ... 21d140b165

 

[hou_ge2000]

From that article is seems anytime energy is used from the battery, it's the least efficient.

The engine first generate electricity by MG1. There is energy conversion lost in the process. Then some electricity get stored in the battery which dissipate some energy in the recharging. Then when energy is drew from the battery, some energy dissipate too. Finally, more electricity is dissipated in the MG2. Therefore, it seems desirable to use as little energy from the battery as possible.

It may be desirable to simply have the engine work the wheel directly or charge MG1 and send the power to MG2 directly with as little battery intervention as possible.

Does anyone know, under different circumstances, what percentage of engine power is

1. going directly to the wheels
2. charging the MG1 and then sending to the MG2.
3. charging the MG1 and then charging the battery

It seems it's beneficial to minimize #3 at all circumstances.

 

[melgish]

It seems it's beneficial to minimize #3 at all circumstances.

When #3 is going on, the energy going to the battery would be otherwise wasted.

 

[unclehan]

Thanks.

What about when the Prius is at highway speed? I seem to think the sole source of power is from the engine, with the motor not doing anything. Is this right?

Let's say the speed and load of the highway operation is perfectly constant, so there require no gear change and the engine can simply run at one rpm. Is the drivetrain just as efficient as a manual transmission? In another word, does the motor have anything effect? I believe the motor (MG2) is connected between the engine and the differential and spins along with the wheel. So doesn't the engine tend to generate electricity with MG2 (just like regenerative braking would do) because spinning the wheels will also spin MG2. Or is the MG2 simply idle and have no effect between the power transfer from the engine to the wheels?

 

[john1701a]

There is no such thing as "perfectly constant" in the real-world.

Highways are loaded with minor (almost invisible) inclines & declines, which the system takes full advantage of... boundless efficiency opportunities. Just that fact alone allows the always present on-the-fly electricity from the engine to be utilized.

There are others. But it really doesn't mean much until you step back a bit. Looking at the big picture, like the electricity being used to top-off the pack, run the lights, fill your interior with music, cool you off, and the fact that most people don't drive at a constant speed anyway, you can start to realize the benefit of a system that provides the ability to use the propulsion-motor for just a second or two.

 

[RSnyder]

At least one motor/generator (and usually both) must be active for any power to transfer from the engine. The battery is heavily involved in rapid changes to requested power (this engine purposely responds relatively slowly to avoid pollution). It is also involved when a lot of power is requested at higher speeds, or when just a little power is requested. Otherwise, it tends not to be much of a factor in steady state (e.g. highway cruising). The combination of motor/generator involvement in highway cruising is pretty small, resulting in transmission efficiency better than an automatic transmission but probably not quite as good as the best manual transmissions. Since it allows the engine to run at its most efficient speed for the amount of power needed, the overall efficiency is even better than that attainable with a manual transmission, except at certain sweet spot speeds. Of course the sweet spot speeds of a manual transmission change with terrain, road surface, wind, etc., so they're rarely attained in real life.

Heavy use of the battery for heavy acceleration (and during engine warmup*) does, indeed result in much lower overall efficiency.

* For the 2001-2003 Prius, I'm not sure if this applies for the 2004.

 

[ken1784]

Hi, I wonder if there are any situations where the Prius is powered solely by the gas engine?

Please refer to following chart...
http://www.toyota.co.jp/en/tech/environ ... tem_03.gif
This is at full throttle.

The ICE torque is always distributed 28% to MG1(generator) and 72% to MG2(motor=wheels).
The most efficient situation is there is no arrow to/from the HV battery and the ICE is running at the ideal speed and torque, then the generator/motor combination acts as a kind of a torque converter.

Regards,
[email protected]

 

[john1701a]

The most efficient situation is there is no arrow to/from the HV battery

An interesting comment to add to that is the fact that HILL CLIMBING will often be in that mode.

 

[DaveinOlyWA]

that is the beauty of the Prius... it automatically routes power in the most efficient manner depending on what your demands are.

this is most evident on the freeway where you will see all possible modes of operation in as little as a few seconds.

those small rises and dips that you never really knew were there until now and the reason you know its there is because all of a sudden you getting 99.9 mpg at 65 mph!!

 

[KenHerrick]

Motor use/how it works

Take a look in the Technical section under "2004 block diagram". I've posted my notion of a power block diagram + my take on how it all works. (Hope you can see the .jpg attachment; my ISP/browser seem currently to be blocking it for me.)

Ken Herrick

 

[zinzindorff9]

Too bad Toyota didn't publish Grahamns booklet (45 pages) about how the Prius works. It answers every single question about the Prius operation with simple terms and diagrams that I've seen posted on this website. Read it and you can even tell a Toyota service manager "how it works!"

 

[KenHerrick]

The explanations

Too bad Toyota didn't publish Grahamns booklet (45 pages) about how the Prius works. It answers every single question about the Prius operation with simple terms and diagrams that I've seen posted on this website. Read it and you can even tell a Toyota service manager "how it works!"

Right...Graham's is excellent. But mine is only a couple of pages + diagram. Maybe good for a start.

KCH