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Originally Posted by tumnasgt
After 15min of thinking, I think I have found the flaw. It takes exactly the same amount of work to go a given distance (Work = force x distance), so it's more about getting the most work from the engine on the least amount of fuel.
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We have to factor in the fact that vertical distance takes more force to get work done, and the longer you spend doing that work, the longer one must sustain that force. The force is generated by expending energy (burning gas).
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That's where DWL comes in, if you drive over a 2 mile distance up hill at 60mph getting 15mpg, you're going to be worse off than driving at 30mph at 25mpg.
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Of course, your efficiency numbers were conjured, and not based on any real world figures.
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As I'm poor and can't afford a scangauge (or even use it in the car I normally drive), I DWL based on throttle position.
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I am without a scangauge because my ODBII port is already being used by Progressive's Snapshot device.
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Originally Posted by basjoos
You also have to account for the thinner, air in the higher elevations of the mountains, which has a huge effect on improving mileage... You know how much your coasting distances improve when going from 10 degrees F to 80 degrees F. Imagine doubling that improvement which is what you would see when going from 500 feet elevation to 10,000 feet elevation.
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I think that is a significant factor, although I have never noticed a difference between coasting in 30 degree weather and 100. Perhaps the effect will be more pronounced now that I know to pay attention.
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In general, I get my best mileage when I climb the hills as slow as I can while still keeping the rpm over 1200, usually at around 70% to 80% throttle. That translates into a speed of 40 to 45mph.
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It follows that if the most efficient way to climb a hill is as slow as possible while over 1200 rpm, then doing it in 1st gear would be most efficient. I find this difficult to believe.
As Brucey has pointed out, dashing up a hill is comparable to a pulse and glide. I still have not heard compelling evidence as to why my practice is inferior to DWL. It must be explainable in a scientific way, or described using a simple scenario such as I have done with my rocket concept.