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Old 05-15-2009, 01:36 AM   #3 (permalink)
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Join Date: Oct 2008
Location: California
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Smart Car ForTwo Pure - '08 Smart Fortwo Pure stripped
90 day: 51.35 mpg (US)

BMW 750iL V12 - '90 BMW V12
90 day: 26.4 mpg (US)

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When hypermiling figures are meaningful

1. Why are you not hypermiling thru Jan. 15? Just curious (guessing you're not keeping a fuel log after Jan. 15 either so it doesn't skew your numbers when you're actually hypermiling).

2. For your vehicle mods...can you post a pic of the springloaded bird thingy? This has to be the most resourceful and odd FE instrument I've ever heard of...that's awesome!

"I use a handheld anemometer to determine the optimum mpg speed. I do not use a tach or Scangauge. I have mounted a flowerpot bird with springloaded wings on the front cowling to indicate turbulence, wind speed, wind direction and drafting sweet spot."
Hi Matt,

When I am hypermiling, I can get pretty fanatic. I seek out roads that allow me to go maybe 35 and I'll drive a long distance at that speed just to evaluate the vehicle's mpg performance. I have kind of an engineering attitude when I do this, thanks to some ME in college, which gets pretty purist. It's not really practical for most of us.

This logging stuff is meaningful only in the relative segments. You need a segment for agressive hypermiling and a segment for driving in traffic and a segment for goal or out and return on a time schedule. It gets so complex that nobody is going to go to all the trouble to record it.

What we end up with on all these mpg logs is a compromise that weights the drivers passion for hypermiling against the vehicle's performance. And since it's a sliding scale, different for each driver, the accuracy always falls withinn a range of error that is difficult to detemine. Still, we can tell a lot from these logs - but my attitude is to not record trips where I am not hypermiling.

For instance, I took a sick person from Los Angeles to a doctor in Phoenix in the summer of 2008 in my Smart. This was not a hypermiling trip. The temperature was 108. I drove 70 mph with the air conditioning on. I think we averaged 42 mpg. Now, if I apply that against my hypermiling scores, where I'm trying to get the best mileage out of the Smart, it brings down my mpg. That does not make sense.

So an mpg log will ask "What is the lifetime mpg of your car?" That is meaningless. The answer reflects various social imperatives of the driver, which has nothing to do with the evaluation of high mpg that we are studying on this site.

In January I took a trip with my daughter from southern California to the Oregon coast, then down Hy 1, hypermiling with the bird. A beautiful trip. We blasted up to Oregon and hypermiled down the coast. It was wonderful. On Hy 1, I think we spent more on coffee than gasoline.

I can tell that you are one savvy guy to bring up the bird. The bird is hands down the best hypermiling instrument I have ever found. And I am a guy who has professionally run pyrometers, exhaust temp gauges, vacuum gauges, turbo boost gauges, instaneous mpg flow meters and even ridiculous crazy **** to try to find the magic bullet. But the truth is, once you get to 30 mph, what really plays with your efficiency performance is the wind vector. The bird tells you both the wind velocity and the vector. No other instrument does. As a soaring pilot for many years, I am fascinated by the bird.

The way you mount the bird is very important. You want the wings to cut the airflow perfectly at 30 mph. Above that, they should start to rise. In a crosswind vector, they will lean leeward. In draft, they will open. In headwind, they will close sooner than in still air. In a tailwind (grin) they will stay open far longer than normal. The bird is your friend. Do the bird.
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