See the Energy Breakdown shots:

Rear Wheel Steering & Headlamps that follow our Steering:  If our vehicles were fitted with solid-state anemometers as shown below or like I show later on, directional headlamps or 'Adaptive Front Lighting' like the demo below or as can be found at http://www.lexus.com/models/gs/exterior.html#frontlighting  & rear wheel steering as illustrated here by Delphi  http://www.delphi.com/manufacturers/auto/chsteer/steering/electric/activerear/ ; then our vehicle ECUs could calculate, like the Synergy Simulator does now, what the 'Corrected Wind Angle' composite is, what the 'TAS' or 'True Airspeed' is and then appropriately steer the rear wheels & turn our headlamps so that the body of the vehicle approaches the Corrected Wind Angle head on.  Calculations show that this can increase vehicle mileage by as much as another 15%.  It might look a little bit like a dog running sideways down the road but, as soon as folks knew that meant fuel savings; it would likely be considered cool technology!  Nice thing is, it would all be automated and controlled by our ECUs.

Adaptive Front Lighting on some Lexus Vehicles.                

To see again, right click on Photo &

choose 'Play' from the choices that drop down.

        Delphi's Rear Wheel Steering                 Solid-State Anemometer                              

Below, the Blue Zire 72 PDA shows the energy breakdown for the 145° wind giving 53.55 MPG.   The Tungsten E unit shows the energy breakdown caused by a wind from 325° resulting in 43.02 MPG.  Notice, in each screenshot how much energy, in particular, is being used to overcome 'Aerodynamic Drag' @ 70 MPH. 

Notice in the screenshot below that I have changed the Fuel $/hr value to $2.65/Gallon by clicking on the '*' and the program updates the cost/hr value immediately.  Notice also that extra information (this is user optional) is available on the Hi-Res Palm devices such as the button showing '04-06 Prius' letting the user know which motive device he is calculating for, the MPG area showing more energy use detail & more.

Graph from Data gathered off maiden voyage of first amperage tracking & logging equipment run in late October 2003 on the new HSD in a 2004 Prius.  This was some of the first data any of us had  to help us know a little bit more about what the new  HSD in the 2004 Prius was up to.  This data changes with ambient & operating temperatures by as much as +/- 20%.

See screenshots showing All Variables involved in Prius Synergy Simulator Calculations.

The  Palm units below show all the Input variables involved, some of which are hidden in the above screenshots.  These units show that the only variable changed to go from 43.02 MPG to 53.55 MPG is an 8 MPH wind direction from exactly opposite directions.

See the Wind Assist screens

The first screen  is provided because sometimes it is confusing to know exactly what number to enter in the 'WDir' or Wind Direction field in the 'Input' screen.  This Wind Direction Assist screen is accessed by clicking on the '*' next to the 'WDir' label out on the 'Input' screen.  If you click on any of the Wind Direction buttons; lets do the '203º ' button; you will return back to the 'Input' screen with that Wind Direction being automatically entered for you & the simulator will recalculate itself manifesting the new results as seen in the second photo below.  Why do we need to bother with Wind Direction input?  Because it is a VERY BIG DEAL.

Notice the 'muddy' kind of color mix as you transition from red to green.  This is purposed as this is an area that can be either detrimental or beneficial to mileage and is governed by a combination of both your vehicle and ambient wind speeds.  The simulator calculates the 'muddy' area for you and lets you know if it is good or bad in your particular situation.   As a general rule of thumb, you can figure that if  you live or travel in a windy area, you have about a 70% chance of having poorer mileage than someone that does not live in a windy area.   A quick check of the simulator will tell you if your winds are helping or hurting.

If you click anywhere in the red/green areas in the first screen above you will get the popup message that shows in the screen below.  There are more than 70 different informative popup screens like the '30/70 Wind Rule' below which provide very helpful information.  

Like the '*' that brought up the 'Wind Direction Assist' screen above, every '*' on the Input screen provides 'Assist' screens where the variables that need to be entered are made more understandable & are automatically brought back to the 'Input' screen and computed into the overall picture.  Currently there are five '*'  that bring up five different Assist screens for difficult things like TRR, RRR, Wind Direction, BTU/Fuel/kWh choices, Cost/Energy Breakdowns and then there are other Assist screens that are accessible with buttons such as the Nomograph, Well to Wheel efficiencies, Aerodynamics, Crosswind Corrections to FA, Cd & even the many effects of Weather and its many, many variables; things like air density, slushy roads & hard rains.  All of these Assist screens allow any user to quickly understand & input variables that even a seasoned engineer would find difficult to calculate without consulting reference texts for formulas & a good scientific calculator or a large pre-programmed spreadsheet full of formulas.    I used to use a large spreadsheet & I thought it was wonderful but, using this Palm Synergy Simulator is not only way more convenient in size and portability but, it provides much more information instantly, graphically & dynamically at the very moment I input any changes in speed, temperature, winds, elevation or any  other variable that is constantly changing in our 'Real World.'

Under covers added to underbody for better aerodynamics.  I colored the covers with light blue so that they would be easier to identify.  The bottom photo is an actual photograph of the bottom of a 2004 Prius.

Aero flow around a 2004 Pirus

See what the MPG will be with No Winds involved 

The first simulator screen below shows the 'Nomograph' which illustrates the RPM of each of the 3 motive devices that power the Prius as they are related through the Planetary Gear system which is essentially the Prius transmission.  Simply manipulate the sliders on the screen and watch the relationships & values dynamically change in real time.  Notice in this screenshot that MG1 (Motor/Generator #1) is running backward @ -3,971 RPM while propelling the Prius forward @ 70 MPH.  The RPM range of MG1 is constantly changing from forward rotation to reverse rotation in direct accord with the speed & engine RPM values.  This is a very interesting and informative screen and reveals some of the depth of engineering ingenuity Toyota has put in the Prius.

The screen on the right shows all the same variables as the shots above but, 'Without' any 8 MPH winds giving us 51.03 MPG.

Notice the 'Elevtn' field.  Elevtn stands for Elevation (not very much screen real estate on a Palm device) or Altitude above sea level.  Did you know that if we were do nothing more than to enter 5,400 feet into the screen on above-right instead of the 400 feet it has now, we would go from 51.03 MPG to 57.29 MPG.  Many of the Western States such as Colorado, Idaho, Nevada, Wyoming, Utah, Montana, the Dakotas, California, Oregon, Washington, New Mexico, Arizona & more have thousands & thousands of miles of freeway at or above 5,400 feet and if you drive carefully on those highways in a Prius, you can get great mileage.  In fact there are many places in Utah, Colorado, Wyoming & Idaho with highways in excess of 7,000 ft. above sea level.  If we were to put 7,400 feet in the simulator we would see that our mileage would go from 51.03 MPG to 60.25 MPG & this is at 70 MPH!  The simulator shows us these things very accurately & very quickly.

Below find some photographs & detail on the Planetary Gear set mentioned above and see how MG1, MG2 & the ICE are mated through the PSD.  The Nomograph shows us how these 3 Motive units relate to one another through the Planetary Gear Set.  This display is from some photos I worked up on the 1997-2003 model years; the 04-06 units HSD™ (Hybrid Synergy Drive™) are very similar and so I have chosen to not update the display.

Sometimes disassembly is what it takes to figure out what's new about new technology!

Hybrid Synergy Drive (HSD)
The most sophisticated production hybrid system is Toyota's Hybrid Synergy Drive (HSD).   HSD is featured in the second-generation Toyota Prius, which launched in 2003 as a 2004 model year vehicle and the Toyota Highlander Hybrid, which launched in 2005 as a 2006 model year vehicle.  Below is a shot of the newer HSD™ (™) Hybrid Synergy Drive.  Notice the electronic AC unit hanging just in front of the oil filter.  It certainly is nice to have air conditioning when in 'EV Mode'  or 'Stealth Mode' during the hot months.  You can see how similar the design is to the 1997-2003 THS™ (Toyota Hybrid System™) unit above.

While we are looking at cutaways; one interesting thing that Toyota does with its highly touted Atkinson Cycle ICE (Internal Combustion Engine) is seldom, if ever commented upon.  I have taken one of their drawings of the Prius Atkinson Cycle engine and colored it up so that we can see that they use an off-cylinder-center-line crankshaft position to help garner the incredible efficiency this engine manifests.  This off-cylinder-centering of the crankshaft allows the TDC (Top-Dead-Center) of the piston to be achieved AFTER the crankshaft has passed its rotational TDC and is in its downward motion ready to better absorb and transfer the already improved Atkinson Cycle combustion forces.

I have been asked several times if there really is very much of the braking energy being captured & put back in the battery through Toyota's upgraded HSD Brake Regeneration System.  I have run a lot of tests and shown a lot of data to the groups over the years so, we knew the updated HSD was significantly better at capturing brake energy than the 'Regen' in the first US release of the Prius.  Recently, I went out and took a photo of my brake pads on the right front wheel after 100,520 miles of use.  These are the original brakes that came on the car.  Fortunately, I had taken a photo of the same pad at 8,000 miles when I was having my tires rotated.  The data I had collected over the last two years told me I was capturing a lot more of the energy that is normally wasted but, as they say "a picture is worth a thousand words."  My normal cars generally go through at least one set of brakes and often 2 sets before 100,000 miles.  At 100,520 miles, I literally could not measure any wear on these pads with my metal mm ruler.  I know there has to be some wear but, it appears that I will have to remove the pads and use a pair of calipers to measure such a small amount.  This is pretty incredible!

Toyota provides an illustration (below) that gives us a general idea of how the Brake Regenerative mechanism operates.  I used to try & make sense of these graphs but, I now leave that to the reader's ability to decipher.  What I can say is; after inspecting my brakes, as can be seen in the above photos, the new HSD Brake Regeneration System does a fine job of capturing the normally wasted braking energy.

See some of the new features in the Palm program's latest release.

Well-to-Wheel Efficiency %

This screen allows us to choose other modern & popular motive systems to see how well they might do under exactly the same variables.  The screen on the right shows us that if we choose to run the 2005 Honda IMA hybrid system in our Prius under exactly the same variables we would drop from 51.03 MPG to 44.07 MPG.  I am excited to see how well the new 2006 Civic IMA system does.   Running this same data for the latest 2005 Gasoline Engines, we come up with 29.86 MPG in our Prius  ... OUCH, that is the technology we use in almost all of our overly ubiquitous SUV fleet here in the USA!

Data for above table taken from:  http://pressroom.toyota.com/publications/2005engine/Well-To-Wheel.pdf

*HSD = Hybrid Synergy Drive - Second Generation Toyota Hybrid System

**FCHV = Fuel Cell Hybrid Vehicle - Toyota's Projected (Not Yet Achieved) Goal for Hydrogen Fuel Cell Vehicles incorporating their latest Hybrid System

Just to show that there is a considerable amount of confusion on Well-to-Wheel efficiency, even within Toyota itself, find below a chart taken from  http://www.toyota.co.jp/en/tech/environment/hsd/04.html .  I use the above chart for now as it is more conservative and a little nicer to current gasoline car efficiency ratings which show 19% above & 14% below.  Do note however, that the 'New Prius' is rated 29% above & 32% below.  All the calculations that the simulator uses shows that the 32% figure below is likely closer to reality but then, all you have to do is change the BTU content of the fuel on the Input screen and you can make the above 29% work also; that is exactly why I have put other vehicle motive systems choices on the screenshot above; so, we can compare real apples to real apples no matter what BTU value we use in the 'Input' screen.

See the per gallon efficiency of  liquid Hydrogen in a Prius.

The screen on the left will allow us to see how well the Prius would do on several different fuels.   If we choose Hydrogen and run exactly the same variables as above, we drop from 51.03 to  13.47 MPG & this would be with a full THS II or HSD, Hybrid Synergy Drive Hydrogen system.     Even if we could afford to carry hydrogen in a liquid state (liquid tanks are heavily insulated, very large, very heavy & way too expensive), we would have to have a 45.4 gallon fuel tank to get as much energy into our Prius as we do with our 11.9 gallon gasoline tanks now.  If we were to 'not' use our THS II hybrid system and go to a normal internal combustion engine, we would drop to 7.82 MPG on hydrogen.  The Palm program shows us all these things very quickly.

A note on hydrogen:  The fuel cells being developed today are actually turning hydrocarbon fuels into hydrogen which is then turned into electricity to run electric motors.  Although the hydrogen industry hopes to achieve about the same miles per $ as gasoline gives us today; the best of them today have 'Well to Wheel' efficiencies that are still significantly less than the 04-06 Prius.  The Prius, as shown in a screenshot above, achieves a Well to Wheel efficiency of 29%.***  The best Fuel Cell systems out are converting at about 21-22%*** (hydrogen fuel cells extract hydrogen from hydrocarbon fuels such as natural gas, methanol, and even gasoline).  The cost of the system is currently & completely out of reason and the cells are presently manifesting very poor longevity.  The industry still has a very long way to go.  The most positive industry representatives say no Hydrogen Infrastructure before 10 years while most others state 15-20 years before the 'Hydrogen Highway' is a reality.  Even Toyota, who has very lofty goals for hydrogen, predicts that that we are decades away form being able to effectively use hydrogen vehicles such as their FCHV.  Until then, hats off to Toyota for making hybrid vehicles which are more efficient than the best fuel cells of the day & already have excellent longevity & pricing.  These hybrids will  help carry us to whenever the Hydrogen Utopia or something else becomes our new energy reality.

***These efficiency percentages, which vary with the source, represent the full  or overall energy conversion efficiency of converting the energy content in crude oil to the final energy being transmitted to the ground by a vehicle's tire or wheel.  For more information on this subject see: http://www.memagazine.org/supparch/mepower03/gauging/gauging.html & http://pressroom.toyota.com/publications/2005engine/Well-To-Wheel.pdf

See the Energy Breakdown with Hydrogen.

The screenshot on the left shows the energy breakdown & cost of running gasoline at $2.95 a gallon which gives a $4.05/hr operating cost @ 70 MPH.  Even if Hydrogen fuel were to cost $1.21 (1989 estimated cost) a gallon/US, we Prius owners would have an operating cost of $6.34/hr @ 70 MPH; this is reflected in the screenshot on the right.

See some more of the Help/Assist screens for data entry

The Help/Assist

The Help/Assist screenshot on the below helps us correctly set the type of Roadway surface we are simulating for.  A heavily rain-soaked highway can rob you of a lot of MPG.  

Almost every label identifying an 'input' field in the program will popup an information screen akin the that shown below.  If you were to click the 'cwCd'  label on one of the above 'Input' screens you would get an 'Info Popup' screen as illustrated in the lower right screenshot.  Crosswind Correction factors or formulas are unique to this simulator.  In fact, I could not find any data or formulas on this subject and I had to fit two different Prius vehicles with anemometers, wind direction equipment & data loggers for more than 30,000 miles (people thought I was a storm chaser) to come up with the formulas & factoring values used in this program.  I have yet to hear of a simulator that has this feature and yet it is such an important variable to know as it 'wildly' affects our mileage for good or bad any time the ambient winds go above 5 MPH.   

SOC pre-staged for upcoming Terrain  

Some of the early SOC pre-staging via GPS-Terrain-Following work begun back in early 2004.  This is part of an actual route followed by a State & University sponsored rally that I had friends participating in and had provided for their use that year.  If you pre-stage your SOC for what is upcoming in terrain, you can really improve your mileage.  In a nutshell, use up most of your SOC before going downhill & get great mileage while doing so.  Now, as you approach your downhill run, your SOC is way down and you can capture more of the normally wasted downhill 'regen' energy that a normally held SOC could not handle.   After bottoming out, hold your newly elevated SOC high until  it is time to begin climbing so as to have more EV or electrical assist available going up the next hill.  With extra Ah of battery power, GPS based terrain awareness, corrected crosswind data & the proper algorithms which accurately calculate & pre-stage your SOC, you can get up to 25% better fuel mileage.  This is a very exciting area that Toyota & Denso jointly have in patent pending status.

Full SOC (State of Charge) & associated voltages showing I/O hysteresis @ 70ºF (varies with temperature ±20%).  The 'Terrain Following' logic is SOC-centric & so it is very important that we know how the SOC for our batteries works.  The illustration below shows a red arrow going up and a green arrow going down (This is counterintuitive to how we usually look at this Icon).  Green shows us the voltage hysteresis of each bar as the Prius gets electrical assist (Green for improved mileage) & Red shows us the voltage hysteresis per Icon bar as the battery charges which 'takes' energy from the ICE or from regeneration.  It should be understood that any energy gained from regeneration was, in almost every case, initially provided by the ICE.  The only natural but often experienced exception to this is, regeneration energy captured from tailwinds.  The SOC % values were determined from my own data collection & that of Attila Vass who's most excellent work on monitoring regeneration amperages vs. speed vs. SOC% can be seen at http://www.vassfamily.net/ToyotaPrius/CAN/rechargeindex.html ; while there take a look at his other astounding work on his Prius & especially the small notebook-like Linux based computer he uses to monitor the Prius' CAN system.

True SOC % per Battery Icon Bar.  This graphical illustration 'stretches' the Icon bar vertically allowing each bar to be better represented by what is happening in reality.  Notice bars 6 & 7 span a much larger range of the SOC than the other bars.  This seeming phenomenon of bars 6 & 7 spanning a larger range than the other bars is what happens in reality.  If you look at the voltage ranges in bars 6 &7 above, you will notice that the ranges are comparable to the other bars & this really doesn't make much sense when looking at the SOC % ranges below.  It all comes together though & begins making sense if we look at a discharge graph for the Prius NiMH battery.   Notice that the voltage ranges for bars 6 & 7 although comparable to the other voltages per bar ranges, covers most of the 'flat' area going from left to right which is indicative of time in those ranges.  Now it begins to make sense as to why we stay in bars 6 & 7 longer.

This kind of system matches very nicely with the GPS based Navigation computer already in the Prius.   If you preset a trip, the Prius already knows your route and only has to be 'aware' of the terrain data along your route.  The system only needs terrain data for an area that is about 60 feet X about 5 miles (dependant upon Ah) to properly pre-stage the SOC  It knows within about 15 feet where your are via GPS location.  It knows how fast you are going,  it knows if there are towns ahead where you may reduce speed, it knows what the ambient temperature is, it knows how fast you have been traveling for the last 5 minutes and last but not least it should also be fed ambient wind conditions.  As can be seen above, crosswinds, headwinds & tailwinds can consume or contribute incredible amounts of energy so, it is very important to add those kind data points to the algorithm also.  I have spent several enjoyable years working on this and some other technology and can attest that with the advances we are making in electronics and etc; all of this will soon be available to us at fiscally responsible pricing & well worth our personal investment.  A Prius that gets 50 MPG will very likely be able to get 60+ MPG using nothing more than this technology.  Most of the hardware is already in a Prius that has the Navigation option.  Add a solid-state anemometer, highway terrain data, some updated code & we are there!   $3.00+ a gallon fuel pricing in the US will likely place this technology into public use even more quickly than without fuel prices rising.

Dual function, solid state anemometers such as in the above photos, make gathering ambient wind data much nicer looking than the anemometer you see on my 2002 Prius.