Quote:
Originally Posted by Phase
Are there are numbers for how much your mpg increases at higher altitude?
Like 2 percent every 1000 feet?
How much better mpg do you get at 7000 feet versus sea level? Wondering if there are any hard numbers
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There are lapse rate 'relationships' between air density and elevation, other than 'standard air' criteria, but you shouldn't use them, except for 'qualitative' work.
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During road tests, actual meteorological conditions in the vicinity should be monitored and documented for post-test data reduction ( lots of mathematics ).
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You really need someone riding shotgun with you, so you can focus on 'driving', while the 'geek in the right seat' searches for, and records the pertinent data. Otherwise, you risk becoming the 'dead' road tester, as well as taking some innocent people down with you.
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Some online air density calculators are available, and they spell out the required data you'll need to supply in order to properly use them.
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* 'Raw' barometric pressure is a critical component ( some reported barometric pressures are 'modified' for the benefit of pilots, for altimeter calibration, conditions they'll be flying into, and are not necessarily what you need ).
* Many airports provide a phone number for the Automated Weather Observation System ( AWOS), but you better understand exactly what it is that they're actually reporting.
* Technically, you'd need the actual local acceleration due to gravity, as it varies with Earth's crust below you.
* A sling-psychrometer can provide wet-bulb and dry- bulb temperatures, which, along with a psychrometric chart can give air mass/unit volume, but you need the local acceleration due to gravity in order to do the division to produce (rho).
* NWS isobaric maps ( online in real time ) can show if you're 'connected' to any region of 'known' raw barometric pressure.
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If you ever get to Bonneville, you encounter Rick Gold's Racing Fuels, who maintains three onsite weather stations that he provides data from to the racers, which they use to calibrate their fuel systems and computerized telemetry for 'current' salt flats conditions.
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When CAR and DRIVER tested Spindletop at the Chrysler Proving Grounds they brought their own scientific-grade test equipment with them. The late Don Schroeder did all test driving while his assistant simultaneously recorded all the weather conditions. They do this wherever they do road testing, worldwide.