Has anyone else done a MPG-MPH chart?
 

Ok, so they didn't make hybrids back in 1997 when I purchased my Civic HX and it doesn't have a digital fuel consumption display. I've always enjoyed calculating my gas mileage and trying out different techniques for road trips to see what the results are, but without an fuel consumption display to do quick, controlled tests, you're kinda limited in what you can research.

Then along came the ScanGauge. It plugs into your OBD2 port and reads the fuel consumption from the ECU. This sounded like the perfect toy for me to play around with so I bought one. It apparently doesn't quite compensate for the HX's lean-burn mode, but the information is still valuable, and I set out to chart the steady-state fuel consumption at various cruising speeds in 5th gear. Using 3 different roads and doing runs in each direction to balance out slope, I came up with the following results:

http://www.autocrossing.com/misc/junk/mpg-mph.gif

Supposedly the lean-burn mode only engages at light load covering speeds upto somewhere around 60-65mph. My chart would seem to probably follow-along with that. I think that the figures are all a bit pessimistic up until you get to the 70+ mph range where they seem to be a bit more accurate. The flat spot from 60-70 seems to be kind of a transitional speed range where maybe it was sometimes able to lean-burn, and sometimes running stoich.

At any rate, most all of you should own hybrids that actually report the fuel consumption correctly regardless of engnie mode, so I was wondering if anyone else has collected data like this? I spent about 2 hours total doing it (2 runs in each direction for each speed, 1-2 mile long stretches) since none of my "ideal condition" roads for each speed range were all that close to each other. Still, for 2 hours of my time, I feel like I collected valuable data that I can use every day, even when I don't have my ScanGauge in the car. Has anyone else done such experimentation and data charting?

Very interesting! I haven't seen any real-life data like this before, but for some time I have been meaning to add a speed field in the database. It would be relative, however. For instance, +20% of speed limit or -10% of speed limit, etc.

I've beeen thinking about this for a while, but am hampered by a rather poor knowledge of physics, compounded by the hybrid drivetrain.

My original desire was to try and gain a handle on the optimum RPM range of the Prius II ICE, since people in the yahoo forums have stated that there is a pretty flat efficiency curve between 1500 - 3500 RPM, but I disagree based on my experience. I also think that the plethora of jokes about slow hybrid drivers confirms my impression, aerodynamic considerations aside (otherwise why crawl up a hill ?)

Not too far from my house I have an uninterrupted stretch of road with about a 500 foot elevation over 3 miles. I am thinking about running that stretch between 30 and 40 mph in 5 mph increments, starting from middle battery SOC, and see what kind of MPG I get. I can estimate the MPG effect from the wind resistance from Wayne Brown's Palm program.

Any advice to improve the method is welcome !

What is the Wayne Brown Palm program?

Hi HG,

Wayne Brown is an engineer/scientist/tinkerer type who was active in the 2004-Prius Yahoo group up until last year. He contributed a Palm program that estimates MPG for a G2 Prius based on conditions entered. It is astoundingly accurate, reflecting a ton of empiric measurements that the author collected, as well as physics modeling quite above my head. From elevation to tire resistance, it's all there, and can be changed at will.

addendum: The program also shows the breakdown of power requirements for a given set of conditions, which I find terribly interesting and useful. It is from this that I can gather how much additonal energy is being consumed at higher speeds.

So far as I know, it has only been written for the Palm PDA. Macintosh has an emulator that can be used in a pinch.

I'm pretty sure I have a zipped file I could send you, and Andy Roberts has the file hosted on his web page. His URL can be found by searching the 2g-Prius yahoo forum

What happen to Wayne? I remember him very well, and actually met him once, along with Coastal Dave. I hadn't been to Yahoo for a long while and we lost touch.

Hi Jason,

I do not know details of why he droppped out of the forums, but Dave the white water rafter - turned - VA gov official (who I believe you have also met) had reason to write him recently to request insight into a topic being discussed, from which I gather Wayne is still active in hybrids, if not on a public scale like before.

You may find this interesting:
http://os2.mystarband.net/mpg-mph2.htm

Do you happen to have Wayne's contact information?

The software's here: http://os2.mystarband.net/ along with other links.

YOU ARE AWESOME!

I threw Wayne's data for 80F into my spreadsheet since that's the approximate temperature for my testing last weekend. Based on how nearly flat the curve appears to be for the Prius, I decided to draw a dotted line from the point where I felt that the ScanGauge was reporting accurately without being thrown off by the ECU's lean burn feature. Lo and behold, the dotted line seems to match up with my recent 55-60mph roadtrip and general observations!

http://www.autocrossing.com/misc/junk/mpg-mph2.gif