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Old 08-12-2014, 04:17 PM   #1 (permalink)
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What's your tons per mile

Since the weight of a cubic foot of air at sea level and at 70 degrees F is 0.07495 lbs, the mass of air displaced by a vehicle with a frontal area of one square foot driving a distance of one mile is 396 lbs.

So this means that my 92 Honda Civic CX (frontal area 19.9 square feet) displaces 3.9 tons of air for each mile it drives down the road at sea level and at 70 degrees F.

Drop the air temp down to 0 degrees F (0.08637) and the weight displaced goes up to 4.5 tons/mile.

Raise the temp up to 100 degrees F (0.07094) and the displaced air drops to 3.7 tons/mile.

Drive from the coast to my home altitude of 500 feet (assuming the temp remained at 70 degrees F) and the weight of displaced air drops to 3.8 tons/mile.

Continue driving up to Asheville in the NC mountains (2000 feet) and it drops to 3.6 tons/mile.

Head on up the road to Denver, CO (6000 feet) and I get 3.1 tons/mile.

Climb up into the Rockies to 10,000 feet and I'm down to 2.7 tons/mile.

An interesting intellectual exercise and directly shows the effect of temperature and altitude on your mileage

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Old 08-12-2014, 04:21 PM   #2 (permalink)
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Yeah, too much math for me.
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Old 08-12-2014, 05:50 PM   #3 (permalink)
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density

I talked with Gilkison last night.He's on holiday,in Oklahoma and thinks he's lost an mpg in the 4RUNNER due to the thicker air, compared to 4,500-ft Radium Springs,New Mexico.
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Old 08-12-2014, 06:56 PM   #4 (permalink)
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I get 4.3 tons with my roughly 21 sqft frontal area at 70*F and sea level. In general, temp seems to have greater effects than altitude. I have less fluctuation than most in both categories, it seems. Never goes below 38 or 35*F here and my normal driving is all sea level to maybe 500 ft. above.
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Old 08-12-2014, 07:01 PM   #5 (permalink)
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I did a hike last week at 7000 feet and 80-85 degrees and it felt like I weighed a ton. We're going for an 8000 foot peak but turned around. The 1/2 mile part gaining 700 feet with no trail scrambling over deadfall was the nail in the coffin. Will try a longer but actually established trail Thursday. Good thing there was a plethora of huckleberries as they make everything better.
On topic I have often wondered if the thinner air hurt engine efficiency more then it helped aerodynamics. In carborator days I think the mixture became to rich but with modern computers it adjusts. You may lose power but gain mpg. One big reason if towing in high elevations a turbo is nice.
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Old 08-12-2014, 09:16 PM   #6 (permalink)
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Quote:
Originally Posted by Hersbird View Post
On topic I have often wondered if the thinner air hurt engine efficiency more then it helped aerodynamics. In carborator days I think the mixture became to rich but with modern computers it adjusts. You may lose power but gain mpg. One big reason if towing in high elevations a turbo is nice.
The thinner air improves engine efficiency if you only need the 10 to 20 horsepower needed to maintain cruising speed. As the air thins, you need to open the throttle wider to produce the same power output, reducing your pumping losses. You get up high enough and you'll be at the desired 80% throttle setting you normally use for accelerating in P&G driving while the engine is only pumping out the 16 horsepower needed for cruising. At this point you're running the equivalent of what would be a 20 horsepower engine if you operated it at full throttle. The turbo just allows you to produce sea level power outputs at higher altitudes, but it doesn't save you any fuel as long as you're using it.
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Old 08-12-2014, 09:36 PM   #7 (permalink)
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Quote:
Originally Posted by Hersbird View Post
I did a hike last week at 7000 feet and 80-85 degrees and it felt like I weighed a ton. We're going for an 8000 foot peak but turned around. The 1/2 mile part gaining 700 feet with no trail scrambling over deadfall was the nail in the coffin. Will try a longer but actually established trail Thursday. Good thing there was a plethora of huckleberries as they make everything better.
There are two lung physiological types. One type is highly efficient at the altitude it is adapted for, but loses efficiency rapidly as it climbs up into thinner air. The 2nd type operates less efficiently at their usual altitude (their owners huff and puff more readily when working hard than those with the first type), but they can climb into thinner air with little loss in efficiency. This second lung type is not as common but their owners can climb up through 10,000 feet and hardly notice any loss in lung power.

I have that second lung type. I huff and puff like crazy when running at low altitude, but can climb up through 14,000 feet with the altitude only taking a slight edge off my lung power output.
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Old 08-12-2014, 10:23 PM   #8 (permalink)
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Old 08-13-2014, 02:14 AM   #9 (permalink)
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Quote:
Originally Posted by basjoos View Post
I have that second lung type. I huff and puff like crazy when running at low altitude, but can climb up through 14,000 feet with the altitude only taking a slight edge off my lung power output.
Really? This is interesting. I huff and puff whenever I run because I'm extremely out of shape. However, when I was say in middle school, I'd run around a lot and get exercise, but I could never run much, because I'd tire out so quickly.

When I go to high altitude though (I've been to ~16000-17000 feet before where breathing was difficult, but 13000-14000 is fine), I seem a lot more okay than other people. Heart rate is noticably faster but I only feel like I'm breathing a little harder, and I don't get the headaches some people get from oxygen deprivation. I always thought this was because my muscles are weak so I'm not burning much energy either way lol. But maybe it's because I have the lung type you mention.
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Old 08-13-2014, 04:22 AM   #10 (permalink)
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I've never heard this lung theory before.

I think I breathe, sweat, and generate heat more than others when I run. At altitude I do pretty good as I've never found difficulty sleeping, eating, or had nausea.

Thursday, weather permitting, I'll see how I do on Mt. Adams (12,300ft). Then I run the Hood to Coast relay next week, and the week after that make a bid for the summit of Rainier (14,400ft). I'm not in good shape, so this will be interesting...

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