Hi Dan,
Quote:
Originally Posted by Dan
. . .
Have you noticed a sweet spot in fuel efficiency at around 47 miles per hour. What I found is that around 47 miles per hour the FE is better than it was at 42, and better than it was at 50. Which leads me to believe that there is a localized maximum on FE between 42 and 50.
For what it's worth, with cruise control on at 47mph, I seemed to be getting over 60 mpg, and at times over 70 mpg.
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Excellent! Can you describe your methodology?
- distance
- level and/or slope
- temperature
- number of runs
I have an NHW11, previous model, and since picking it up in October 2006, I have been making a study of MPG vs. miles per hour:
What the above chart shows is the dip that happens at and around 42 miles per hour. For both of our Prius, this is the transition speed between: (1) alternating gas and electric mode, and (2) gas must run mode. If you think 47 is great, you should try it at 38 or slower.
Over a flat, 2.5 mile, controlled section:
This chart is important because it shows what happens when you don't transit 42 miles per hour. The test was very carefully crafted on a flat stretch without wind or elevation changes. This is pretty close to the limit of what the car can achieve at each speed.
But more recently, I've been working on a math model and gotten:
You'll notice there is very good agreement with the measured, 2.5 mile benchmark results. Since then, I've investigated 15 miles per hour and achieved:
This agrees very nicely with what the model predicts. Best of all, I can hold the vehicle in this range as long as I want.
If you'd like some more details and metrics:
http://hiwaay.net/~bzwilson/prius/pri_test.html
BTW, Hobbit is an excellent source. He is pretty good about taking measurements and has done a lot of admirable work:
http://techno-fandom.org/~hobbit/#prius
What I like most is Hobbit's attention to detail and measurements. Sounds like you may have interest in that area and we sure could use the company. Another favorite hang-out is:
Prius_Technical_Stuff - a Yahoo group,
http://groups.yahoo.com/
Bob Wilson