Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

RobertSmalls · 09-11-2009, 10:53 AM

I do love seeing mountains of data, but I have a few questions about, and issues with, your plots.

Is the "actual" data the mpg according to the pump and odometer? There's error in pump data too, but it will be random, not biased, and it'll average out in the long run.

Most of your outliers in the 54-65 mpg range do not look like outliers. They fit the trend pretty well. Also, all of the outliers are on the same side of the trendline, and by excluding them, you move the trendline up. I would actually include them all. If you think one of them represents an incompletely filled tank, you need to throw out that data point and one for the tank that follows it.

That's a pretty scandalous conclusion: The Prius' onboard instrumentation lies about MPG. Is Toyota aware that the community is aware of this? I would write them a letter.

If the transmission had discrete gears, plot 3 would be simpler, and I'd slap you for fitting a high-order polynomial to it. In fact, I think I will anyway. Gears or no gears, work (y) required to go speed (x) is a parabola, and your trendline should be as well. Also, what's up with the guy at 50mph, 70mpg? Is he P&G'ing, or aeromodding, or lying, or what?

When I make mpg vs mph plots, I definitely use gal/mi vs mph. I believe they make more intuitive sense that way.

Plot four: it's good to see the numbers confirm what I had been hoping: The Insight outperforms EPA estimates, and while it doesn't beat the Prius, it's not a total embarassment to Honda.

Plot five: What happens when you compare your hill-climb data to mpg vs mph on flat land? At what speed to you most efficiently convert gasoline to gravitational potential energy, and how dramatic is the difference across the range of speeds you would consider climbing hills? And what's up with the second line where the guy gets better mpg at 88mph than at 83mph?

What are you using to gather data to the 0.0001 of a gallon? That's pretty impressive. Me, I'd like to hook up an ABS wheel speed sensor to a data acquisition card and measure the energy consumption of a pothole.

09-11-2009, 10:53 AM	#3 (permalink)
RobertSmalls Left Lane Ecodriver Join Date: Aug 2008 Location: Buffalo, NY, USA Posts: 2,257 Prius C - '12 Toyota Prius C Thanks: 79 Thanked 286 Times in 199 Posts	I do love seeing mountains of data, but I have a few questions about, and issues with, your plots. Is the "actual" data the mpg according to the pump and odometer? There's error in pump data too, but it will be random, not biased, and it'll average out in the long run. Most of your outliers in the 54-65 mpg range do not look like outliers. They fit the trend pretty well. Also, all of the outliers are on the same side of the trendline, and by excluding them, you move the trendline up. I would actually include them all. If you think one of them represents an incompletely filled tank, you need to throw out that data point and one for the tank that follows it. That's a pretty scandalous conclusion: The Prius' onboard instrumentation lies about MPG. Is Toyota aware that the community is aware of this? I would write them a letter. If the transmission had discrete gears, plot 3 would be simpler, and I'd slap you for fitting a high-order polynomial to it. In fact, I think I will anyway. Gears or no gears, work (y) required to go speed (x) is a parabola, and your trendline should be as well. Also, what's up with the guy at 50mph, 70mpg? Is he P&G'ing, or aeromodding, or lying, or what? When I make mpg vs mph plots, I definitely use gal/mi vs mph. I believe they make more intuitive sense that way. Plot four: it's good to see the numbers confirm what I had been hoping: The Insight outperforms EPA estimates, and while it doesn't beat the Prius, it's not a total embarassment to Honda. Plot five: What happens when you compare your hill-climb data to mpg vs mph on flat land? At what speed to you most efficiently convert gasoline to gravitational potential energy, and how dramatic is the difference across the range of speeds you would consider climbing hills? And what's up with the second line where the guy gets better mpg at 88mph than at 83mph? What are you using to gather data to the 0.0001 of a gallon? That's pretty impressive. Me, I'd like to hook up an ABS wheel speed sensor to a data acquisition card and measure the energy consumption of a pothole.