MFD Energy Graph; MPG-H, A Better Way?

This subject as come up in the past, but here's a different perspective.

I've been driving my 2008 Prius for just over a month now. At 1000 mi. my overall average MPG is 42.3. Good, but not great --- I'm getting better.

At first I was entranced by the golly-gee, whiz-bang displays on the multi-function display, MFD. I was especially pleased by the big fat bars on the energy display as I rolled up to the parking garage after my morning commute. The ride is about 40 minutes; half the mileage on secondary roads, half on the freeway, with about ten minutes of downtown Baltimore traffic at the end. Usually I can get those last two bars on the energy graph up to 100 MPG. I felt real smug as I swaggered into the shop where I work. Still, deep down I was not happy with the 42+ mpg .

Admittedly I've got a lot to learn and put into practice on the driving techniques. While studying up and thinking on various and sundry things in the MPG-ish line, I came to a slow realization that the MFD's energy graph is misleading. It plots MPG against time, and I could have gone 5 miles at 60 MPH in one 5 min. segment, and 1/4 mile at 3 MPH average in the next.

To my mind, the graph would show more useful information if, while the horizontal axis continued to show 5 min. time intervals, the separation between the times were scaled to reflect the miles travelled during the interval.

At the end of my morning commute the graph might then show two big fat bars reflecting 10 min travel at say 40 MPG and traveling 8 miles, followed by two very skinny sticks reflecting 10 min travel at 100 MPG but actually moving about a mile. The relative weight of the bars would be reflected by their area not just their height.

The graph would then show something like Miles per Gallon-Hour, MPG-H. (Maybe not, I get a headache just thinking about it.)

At any rate, it would be not hard to assume that the big fat 40 MPG bars meant far more than the skinny stick 100 MPG bars in determining average MPG, and you'd be right.

FWIW

 

In my original post I was struggling to describe the type of graph that would show time, MPG, and distance traveled info together. I have remembered that it is a three dimensional bar graph. Pretty much any spread sheet program has a graphing function and the help section should show a graphic.

I 'm going to respond to posters. I'm a newbie to this posting business and don't yet kow how to extract qotes, so I'll proceed without quotes.

Tom,

Thanks for your post. Although we seem to fundamentally agree that that the energy display isn't nearly as meaninful as it could be.

That said, I'm going to stick with "misleading. " I am unimpressed that the MPG info is presented "clearly," to my mind that is not enough. The energy display presents MPG data in such a way that starry-eyed new Prius owners --- and that included me --- are lead to believe that 5 minutes of 100 MPG is meaningful when without a miles travelled component the number is merely interesting, and perhaps even trivial.

Further, I find the energy display disappointing. My Prius is at the leading edge of fuel economy and clean air technology but with the energy display I'm given is a trailing edge tool to understand the Hybrid drive and maximize system potential. OK, Toyota provides this simplistic tool so that new drivers aren't inundated with as yet meaningless information (For the first weeks, that was me in a nutshell.) What a waste of valuable space is the energy screen. The info it displays would loose nothing if it were compressed to cover half, one-third, even one-quarter of the screen. The available space could be used to display valuable, much needed info such as ICE and electrical equipment coolant temps, RPM, Ignition timing, throttle position, etc

I've gotten over the goofy-grin stage stage of ownership and I want more meaningful information. It is unfortunate that I have to look elsewhere for a tool that will provide it.

Evan,

Thank you too. From reading many threads I understand that the CAN View is a powerful tool for presenting technical info. Unfortunately, I'm not competant to do the work to get a system up and running. You can be sure that as soon as there is a plug-and-play system that slips into the box below the radio, I'll buy it. Even better would be the system that was being developed in Japan and displayed its info on the MFD.

For now, I've purchased a ScanGauge II so I can do a whole lot better during those many other miles where ekeing out a few more MPGs will be meaningful in the long run. Just by monitoring RPMs during acceleration I've been able to raise my daily MPG by 3 MPG --- daily and current trip info being but a two of the FE-related readings calculated by the ScanGauge II.

 

Winston and ph43drus, thank you for your posts.

At the time of my first post I was frustrated by being mired in the low 40's MPG. So, I did somethings to change it. First, as recommended I pumped the skins up to 42/40, good for maybe 3 MPG. Then I purchased a ScanGauge II from the store. While waiting for it to arrive, I got my grill blocking ready. In less than a week I had both installed. In 40F temps I got another 3 or so MPGs. Things were getting very interesting.

As you know, the hypermilers have identified a number of successful strategies for getting the MPG way up there, even to 70+ MPG at 65 MPH. Frankly, I do not yet understand most of what they are talking about, nevertheless be able to adopt their practices. I did find something, I think it was by the sainted Hobbit, that spoke about a high efficiency sweet spot in the RPM graph that runs from roughly 1700 to 2300 RPM.

So, I implemented a program of accelerating up into this range when ever I needed to use the ICE and trafffic permitted. I used pulse and glide, and sub-42 mph stealth as well. Bingo! On a daily basis, out and back, I'm getting 50+ MPG. Best day so far, 53 MPG. Close to a 25% improvement. I can live with that. Only 5 MPG, about half the gain, may be attributable to my access to RPM info. (I've kept the MPG gain attributions hazy because I am aware that other factors, subtle and gross, may also be at work; slight rise in temps, maybe a tail wind on some evenings, etc.)

What irks me to no end is I don't have access to something as simple as RPMs on the MFD. The whole energy screen is a laughable waste of valuable display area. The only thing useful there for managing MPG in real time is the instantaneous MPG on the far right. All the rest is history, it is about as useful as trying to drive forward by looking in the rear view mirrors.

iMPG is available as a numeric readout on the consumption screen. And its really useful there. I'm zipping along in AM traffic at about 55 MPH and trying to get the most out of the three ICE-off glide states, and being kind of successful. At one point, the ICE is on and my eye falls on the iMPG readout. It says 89 MPG. Thinks I, this is something I can live with, and I shift over to trying to sustain that number by gentle gas pedal changes. Jeez, I can do it, even keeping MPG above 70 up a long slight incline. I'm lovin' this! But once again, all this is wholly wiithout the energy screen.

What I'd like to get on the MFD are some of the other measures that are said to be useful, even necessary, as you press into the 60+ MPG range. As I recall those are throttle position, ignition timing, manifold pressure, and maybe the phase of the moon. (hehe) I like that the Scangauge displays those readings and others, but its low tech readout can be hard to read --- and it sure clutters up an otherwise clean dash. Gimme the info in high res any day. Currently I show ICE coolant temp, RPM, throttle position, and ignition timing. I hope that in time I may be able to discover the meaningfulness of the latter two and work them into an integrated approach.

I would gladly pay Toyota another ~$150 for a energy screen soft/firmware update.

Anyway, I'm really happy with the Prius, and I will in time get beyond this info related aggravation.

Thanks again for your patience and input.

 

For the past two weeks I have been trying to find a reason to soften my position that the energy screen is not very useful. Very glitzy, yes. Very clear, yes. Very helpful, no. It provides no information on which to make a decision about how to manage vehicle energy supplies, given the status of the ICE and HV battery right now, for best MPG.

I keep thinking that I must be missing something, but try as I might I can't for the life of me see what it is. Perhaps someone could explain how a conglomeration of instantaneous MPG figures dumped into five minute bars is a meaningful teaching tool.

As much as anything, the energy screen reflects topography; going uphill = lower MPG, going downhill = very good MPG, on the flat and near-flat it depends on your FE skills. And those you develop using the iMPG figure that is available on the consumption screen. The energy screen shows a generalized view of what I did, but it in no way helped me do it.

I do sometimes use the energy display, but never more than twice a day. If I remember, I'll look at it just before I shut down after my am or pm commute. Seeing those big fat bars has some deep-seated attraction, kind of like a gold star and an accompanying warm fuzzy glow. If I forget and shut down, the info is gone. However, the ScanGauge stays powered up for some few seconds and I can still review data for the tankfull, yesterday, today, and the trip I just completed.

 

This new thread provides what I believe is a clear picture of the low value of the big fat bars on energy screen for energy/vehicle management:

http://priuschat.com/forums/fuel-economy/42944-my-first-100-mpg-bar.html

Granted the trips were at the extremes of the MPH range; in one case ICE-off glide down a mountain, the other 18 MPH in a flat park. What do the graphs teach? Well, that when the ICE is off, you're not using much fuel. ( Interestingly, a ScanGauge would have shown 999 MPG.) In the second case it is possible to get the theoretical max-MPG at theoretical best speed as given in this graph developed by Bob Wilson: (The red line shows max MPG)

http://hiwaay.net/~bzwilson/prius/calculated_MPG_Rev_A.jpg

I'm sure that it was exciting fun tp get six big fat 100 MPG bars on the energy screen in both cases. But I'm still unconvinced that any meaningful learning took place.

Am I beating a dead horse? Yes, most definately. But in my humble opinion, that isn't enough.The energy screen is such a tired old nag that it deserves to be put down, buried, dug up, dismembered, and then beat with one of its legs.

 

freshspeedo,

not to worry, you have the same OEM screens on the MFD (Multi Function
Display) as we do. I guess we're speaking a little cryptically. I'll try to
explain.

On the Energy Monitor screen, the one with the wheels, ICE (Internal
Combustion Engine), battery, and "Electric Motor" (This symbol really stands
in for two electric motors, which can act as generators as well.):
* "No-arrows glide" is when you're moving along and there are no arrows
of any color showing.
* "Yellow arrow glide" is when energy is flowing out of the battery,
through the Electric Motor and to the wheels.
* A "Blue arrow glide" is usually called "regen" as energy is flowing from
the front wheels, through the Electric motor -- now acting as a generator --
and into the battery. You also get "regen" when you step on the brakes.
* Orange arrows indicate energy coming directly from the ICE. Hardly
anybody refers to this state, although it is essential as ultimately, all the
forms of energy that the driver coordinates -- chemical (gas), electric,
potential (sitting at the top of a hill), and kenetic ( the energy in the mass
of the car while it is moving) -- comes from the gas tank, and goes either
directly to the wheels or goes through one or many conversions.

On the Consumption screen, "Fat yellow bars" make up the histogram of past
FE/MPGs shown in 5 minute increments.

If you've read through the previous posts, you'll know that I think that this
arrangement is, well, stupid and wasteful -- YMMV ("Your Mileage May Vary,"
meaning, you may not agree.)

Hope this helps.

 

The following is an exchange on another thread. I'm reposting here because
I think it has relevance to this discussion.