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FJR Motorcycle Forums
Technical & Mechanical Problems
MPG sensitive to intake air temp
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<blockquote data-quote="BwanaDik" data-source="post: 556971" data-attributes="member: 13660"><p>Somewhere in the distant past Jestal made a comparison about gas mileage and riding at altitude. I've searched diligently but can't find it. IIRC, the higher gas mileage at higher altitudes was because of less air resistance because of thinner air (no shit). I've seen the same when riding from Houston to Breckinridge. The mass of the bike and rider are the same so it would take the same energy to accelerate it and keep it at a constant speed in both locations. But thinner air allowed for less drag so less power at constant speed. I haven't done the math but could it be that the cold air is dense air having anything to do with it? Yea, a bit of a stretch but maybe?</p><p></p><p>OK, just looked up some air tables and it shows air at sea level and 40F is about .080#/ft3 and at 70 F it's about .075#/ft3 so about a 6% increase as it gets colder. About the same (only backwards) of going from sea level to about 2000 feet in elevation.</p><p></p><p>You didn't mention how much of a decrease in MPG you got or what the temperature of "cold" and "warm" were. These are pretty small changes so they could be over ridden by simple observational error. But a thought no less.</p><p></p><p>For all you anal retentive tire pressure types, when I get REALLY bored here at work I'll gin up a table to show what you should expect when you fill you tires on the top of Mt. Sandia on a cold day and then ride to the lowest point in New Mexico in the heat.</p><p></p><p>Where's El Toro?</p></blockquote><p></p>
[QUOTE="BwanaDik, post: 556971, member: 13660"] Somewhere in the distant past Jestal made a comparison about gas mileage and riding at altitude. I've searched diligently but can't find it. IIRC, the higher gas mileage at higher altitudes was because of less air resistance because of thinner air (no shit). I've seen the same when riding from Houston to Breckinridge. The mass of the bike and rider are the same so it would take the same energy to accelerate it and keep it at a constant speed in both locations. But thinner air allowed for less drag so less power at constant speed. I haven't done the math but could it be that the cold air is dense air having anything to do with it? Yea, a bit of a stretch but maybe? OK, just looked up some air tables and it shows air at sea level and 40F is about .080#/ft3 and at 70 F it's about .075#/ft3 so about a 6% increase as it gets colder. About the same (only backwards) of going from sea level to about 2000 feet in elevation. You didn't mention how much of a decrease in MPG you got or what the temperature of "cold" and "warm" were. These are pretty small changes so they could be over ridden by simple observational error. But a thought no less. For all you anal retentive tire pressure types, when I get REALLY bored here at work I'll gin up a table to show what you should expect when you fill you tires on the top of Mt. Sandia on a cold day and then ride to the lowest point in New Mexico in the heat. Where's El Toro? [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
MPG sensitive to intake air temp
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