Hi,

You're on the right track and don't be too anxious about how quickly you master the car. If you can get into a set of reproducable patterns, you can treat each as 'an experiment.' Thus I fill-up twice a week to keep my commuting miles separate from my highway miles. This way something I do for one does not get affected by something done in the other period.

Do use the GH database and you'll have a record and notes to keep track of what happened and your progress.

The Prius transaxle has a small number of moving parts controlled by a sophisticated computer. As such, ordinary thinking doesn't quite work. I don't have the URL handy but Graham wrote up a great piece. But let me offer a simplified explanation:

1. The Power Split Device (PSD) is a planetary gear with the center sun gear operated by MG1; the planetary carrier and idler gears operated by the ICE; and the power output ring gear connected via a sophisticated chain to MG2 and the rest of the fixed driving gears.
2. MG1 is used to start the ICE and balance 1/3d of the ICE torque (aka., this is required for the ICE power to be used) and MG1 generates power from the engine alone.
3. The MG1 PSD means that when the ICE is running and the car not moving, MG1 is turning in the reverse direction, very fast. This is 'neutral' or 'clutch in' in any other car.
4. When the computer commands MG1 to 'make torque', it provides a pivot force for the ICE so the ICE torque goes to the ring gear and the wheels. Also, due to the gearing, the MG1 torque and power is also going to the wheels to move the car forward (NEAT!!!).
5. Because of the gearing, MG1 in the NHW11 could fly apart (or generate excessively high voltage) if the ICE was not turning and the car going above 42 mph. To protect MG1 (and the power electronics,) the ICE is always running at least 1,000 rpm at road speeds of 42 mph and higher.
6. MG2 works like an assistant motor and also handles regenerative braking.
7. The same computer controls MG1 and MG2 so sometimes MG2 is generating power for MG1. This typically happens at highway speeds.

BTW, learning about the Prius transaxle can make your 'head hurt' but it is a wonder of sophistication and efficiency compared to ordinary automatic transmissions. A manual can perform better in some environments but requires the operator to handle the clutch.

As for warp stealth, I hope to provide an independent report about it in my NHW11, 03 Prius. It may or may not be in the control laws. But I have the instrumentation to document the phenomina now that I know what to look for.

GOOD LUCK!

Bob Wilson


ps. Some of my most recent work in Prius transaxle investigations:

http://hiwaay.net/~bzwilson/prius/pri_tt.html

 

Bob, thank you for your nice explanation.


There is another one written by Graham...
http://prius.ecrostech.com/original/PriusFrames.htm
[Understandig the Prius] -> [Continuously Variable Transmisson] or [The Power Split Devoce]
These pages are also good teacher.


Ken@Japan

 

I just returned from my first long road trip with my Prius. On the trip from Pamama City Beach to Atlanta I put the Cruze control on and averaged 70 - 80 MPH during the trip. When I filled up the average milage was 46 MPG. On the return trip, I tried a lot of stealth glide and let the speed vary with the terain. The milage was definitly better, I still have most oof a tank of gas and averaged 52MPG indicated. It is good to know that the car can get more than 50 MPG at over 70 MPH and I am still learning to drive it. Thanks for all of the threds and discussion about stealth. pcflorida

 

Thank you for your report.
Let me comment some...
There is 1000ft altitude change between Pamama City and Atlanta.
We have to use some fuel to get the potential energy to climb 1000ft, and we can use the potential energy to go down hills.
We could get the best mileage comparison on no altitude change route, ie; loop route, not one way.

Ken@Japan

 

I would like to calculate the gasoline energy equivalent of descending 1000 feet (for example) in Prius. I have attempted such calculations but the result is much less than I would have expected. If someone has an analysis of this, it could avoid the correcting of possible errors in my calculations.

Leadville, Colorado in the US has an elevation of about 10,200 feet. It may the highest place where gasoline is sold. In an energy sense, such gasoline may be worth more!

DAS

 

OK guys,

Time for me to report my numbers and experience with my new Prius. I could not find a better thread where I could postthis, than the one where I had initially seen PG technique being discussed and commented upon.

I wont say that I have mastered the PG technique in my two weeks of driving the new Prius, but I have certainly tried successfully to drive the car in "no input energy" mode for a good extended peiod of time, driving sometimes to a distance of 0.5-1.0 mile.

My current MPG from the OBD (which I am assuming to mean as 'On-Board Display') is 64.0mpg. I had 64+ mark, but severe rains in SE Texas destroyed this number. Regardless, I am very happy with the number especially since this is my first tank (dealer's gas!), and I have 2 bars left and have driven close to 500 miles!

Most of my driving is in the city - hence very good for the MPG numbers! I have not dirven much on the higway except for very short segments, but I have come to see with my limited experience that the MPG numbers dont look that great on the highway, as expected from the EPA MPG numbers on Prius, as well as the general experience of the community. I plan to be dirving more on the highway, and I really interested in learning the "warp stealth" mode now.

Bob was advising me earlier not to get too anxious about learning PG technique, but I could not help I read a lot about PG before even I bought my Prius, and now I am practicing PG everytime I drive!

Would you guys be generous enough to help me out with the warp stealth mode this time around!

This forum and the people here have been a most wonderful source of information and help to me in improving my driving techniques and me helping out with keeping the environment clean while I save my pocket from being bitten bitterly by the rising gas prices!

Cheers!

 

Excellent progress! My only suggestion is to try and keep closer to 65 mph than above. In the NHW11, something bad happens above 65 mph but I don't have it diagnosed, yet.

I was more concerned about getting familar with the car first but HEY! GREAT PROGRESS!

I can't help on the warp stealth mode. I've not tried to master it.

Bob Wilson

 

Hi Bob (and others!),

Thanks for your encouragement and your mentoring the less-experienced!

Can you offer an explanation as to what the warp-stelath techinque is? It might be difficult to master, but I guess, it wont hurt to get to actually know what it is ...

I have not driven more than 65 MPH yet, since this is a new car, and although it is different than the conventional cars, but it still has a gas engine, and I am giving it sometime to break in, and I would not accelerate to such high speeds...

My wife is currently out of town. (the Prius was delivered while she was out - so, currently, the Prius has had only one driver). I hope that the MPG numbers remain same, or better still, more than their current average - but really, I fear otherwise! My wife did not like me coasting with my old conventional car .. so she might not like me practice the PG technique now as well ... in fact, she might even encourage me to dirve 65+ MPH on the highway .. but I got to put my foot down on that one (not on the accelerator though!

 

I'm watching for that too. I've had my car 2 years and this is the first I've heard of Warp Stealth.
And right she was, shifting a car into Neutral while on public roads is ILLEGAL in most states and UNSAFE in all states. You can safely do it if there is absolutely no traffic around but you better not have a brain fart and forget it is in N.

However, putting a Prius into GLIDE more is not illegal nor unsafe. You have not taken it out of gear. In fact, your foot HAS to be on the accelerator so it is actually safer than setting the cruise control and taking your foot off the accelerator since you have instantaneous acceleration if needed.

She might still have an issue if you are bouncing between say 25 and 40 MPH with P&G though. If there is any traffic, you are likely to tick off a bunch of people. You might gain by having your engine off for an extended period. Presuming they don't put it in N, they won't gain anything going ever slower until you pick up to top speed again. Then they have to use more gas to get up to speed. It takes more energy to accelerate to a given speed than to hold it. We need a Prius lane so everyone can P&G in unison!

 

We are getting more information from the author but it appears to be finding an operating mode that maximizes low-speed, high torque engine operation. A more descriptive term is 'sweet spot' and 'warp-stealth' was just finding and passing through the 'sweet spot.'

I am not ready to give more details until I can replicate the methodology. The author 'Hobbit', uses a vaccum pressure gage, fuel injector monitor and tachometer, all custom instrumentation added to his NHW20 Prius. I seriously doubt it can be achieved with the stock instrumentation.

If you are seriously interested, the Prius_Technical_Stuff YahooGroup is the best and most accurate source. BUT it is a pretty technical group and we assume folks have fair technical skills.

Bob Wilson