Tuesday, July 15, 2008
Thursday, July 10, 2008
Please somebody be less lazy than me and read the original article and tell me I'm wrong and these turn off when nobody is moving around them...
UPDATE looking at the page translated by google for the product it doesn't seem like they turn off the lights when no motion. Booo.
Still though, it's nice that they are touting the low energy consumption
Wednesday, July 9, 2008
However, as always, I say make the changes that make the most sense.
When I heard a friend describe a relative as complaining about the 55mph minimum speed limit being too high because he wanted to drive his prius slower, I had to address mpg vs. speed here.
Each car has it's own mileage to speed continuum. However, for most cars it looks something like the graph below from fueleconomy where it starts to go down after a certain point.
A large factor in this is wind resistance, so cars that are like big air dams (pickup trucks cough cough) are going to have a lower speed at which mileage begins to decrease rapidly. More aerodynamic cars like the prius are going to have a higher point. A forum poster graphed his mileage in the prius here http://www.greenhybrid.com/discuss/f10/mpg-vs-speed-hybrid-driving-strategy-14276/ and claims that the speed of diminishing fuel savings is around 70mph.
So yes, you get better fuel mileage driving more slowly, but it really depends on the speed. So slowing down from 75 to 70 will save in just about any car. Slowing down from 65-60 in some cars, and 55 to 45 will not save nearly as much) Wind resistance goes up as the square of the speed so the higher the speed you'll use significantly more. This is why race cars are so intent on drafting (though I don't recommend drafting on semis, you don't get very good gas mileage when they have to slam on their brakes and you end up smashed, though I guess if you survive and are attached to their truck and your back wheels still work and you are going where they are...)
Plus as always here at "tha metric" we have to consider the other external costs. What about the drivers with road rage behind you that have to make an extra trip to the hospital for their blood pressure? c.f. Denis Leary's song lyrics: "I drive really slow in the ultra fast lane
While people behind me are going insane"
and would you do more for the environment by getting there 10 minutes earlier and spending those ten minutes planting a tree?
Answer due in homework bin by friday.
PS to clarify any agenda you may think I have or do not have, I generally drive the speed limit, as I think speed differential is dangerous but I also want to get there today and not use too much gas.
While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.
You can assume that each 5 mph you drive over 60 mph is like paying an additional $0.30 per gallon for gas.
It uses the principles of biofeedback (which in my mind are: that which we can measure we can learn to control) to try to get us to save gas. It tells us our current mpg, logs it and records it in novel ways to give us driving challenges.
I have found my own little obsessive game with my trip odometer which tells me average mileage, which I have stopped resetting so that I have less control over the mileage so I don't spend my whole drive worrying (little changes with large divisor make littler changes).
An even simpler game comes with the "eco mode" light. a little green indicator that tells me my car is using only 3 of it's cylinders. I recall that toyota has decided to put "eco mode" lights in all their cars (saying when you are using small amounts of gas) as they have found people drive better when they are reminded they are doing well. question of the day: compliment people when they are eating a little and they will lose weight?
Anyway, this new product provides even more encouragement for you to lose weight on the foot pedal (metaphorically speaking).
However it will lose weight in your wallet as well.
At $299 (cnet offers an alternative product that does less for $169) I would have to save 10% of my gas mileage in order to pay back the $299 in a year (assuming 10000 miles driven and 32mpg, your mileage may vary )
By plugging into a vehicle's diagnostic port, it can display miles per gallon as well as trip information and even the cause of engine problems.
But really it's designed to make your driving habits more energy-efficient.
The PLX Kiwi shows off feedback on how you're doing in that regard and gives you a "kiwi score." It's also programmed with 20 increasingly difficult challenges to optimize your score.