Holie Crappy MPG's, Batman!

[the Ferret]

I rarely ride below 8,000'. Less oxygen at altitude means less fuel is required to maintain the stoichiometric ratio. Or something like that.

My current altitude is 201ft. I have never got better than 42mpg. My bike also has always run rich.

My new phone has a compass and an altimeter in it. After reading this thread I pulled it out to see what the elevation I normally ride at

800'. That's 600 feet above Carguy, but a whopping mile and a half below LongRanger. Amazing.

[izmash_imp]

live in salt lake, 4500ish' averaged 43-46 sometimes 50 if im riding like a sane person.

[LongRanger_imp]

My ride this past Saturday was mostly at 5500-7500'. 183 miles used 3.3 gallons, so about 55 mpg. I don't think I went above 70 mph.

[husky385_imp]

I live at around 350 feet and I weigh 165 pounds. This winter I've ridden between 350 and 1500 feet. today's ride 150.3 miles and 55.8 mpg. This month 1445 miles at 52.2 mpg.
Kevin

[Motogeezer1949_imp]

I'm averaging 49.6, even with all the mods I've made, a one tooth smaller front sprocket and I don't ride like an old lady

[rbike_imp]

There is no legitimate reason for such vast different mpg (especially on the high side) other than driving style & speed or there must be something messed up in the FI or computer. Science is science.

Speaking of which - Altitude. When one goes up the air gets thinner. There are basically 3 types of aircraft engine types - reciprocating, turboprop and turbo fan. Very few turbo jets outside of 3rd world, but even those are disappearing due to fuel costs. Recips function best down low, turbo fans are actually a combination of a many bladed shrouded turboprop (80%) with a turbojet (20%) and function the best the higher they go due to the decreased wind resistance on the airframe - it has nothing to do with the engine. Turboprops are the best in the middle altitudes to low high altitudes.

Recips die as the altitude goes up and need to lean out or they will foul. Our bikes do not go fast or high enough to take advantage of the less dense air at altitude on the scale of jets. One has to go to 18,000feet up before the air density drops in half. It only drops 17% to 5,000, but at 40,000 it has dropped over 5 fold (81.5%). It is the air resistance removal that is responsible for the higher "mpg" and increased speed. The different engine and propulsion types are strictly enabling combustion as air density decreases.

Back to our CB & altitude - Our bikes will lean out accordingly via the FI/computer, but it will take a larger throttle movement to enable the same amount of fuel to be consumed to produce the power required for the given load. Think of it this way - every gallon of gasoline has XXX amount of energy in it. To produce a given net load (speed for a specific weight) an exact amount of gasoline needs to be consumed. It doesn't matter if it is on a Harley or a CB or an auto. The different mpgs are a result of their mass speeds and how efficiently they transfer the energy consumed to the propulsion. For similar CB models, the mpgs should be nearly identical at the same speed with the same rider weight. When starting, stopping, driver weight & behavior are non-similar, the numbers are all over the place like on this thread.

[4 Paws_imp]

Ran ethanol free fuel. - got shade over 55 mpg.
Regular gas - 52 mpg.
No drastic changes between rides. Similar weather, terrain, altitude, and speed.

[Nemo_imp]

For the record the title of this thread should be "Holie Crappy..." Holie as in full of holes. Somehow it kept fixing itself...

[the Ferret]

really? That's my fault. I thought "Holy" was misspelled and it bothered me so I fixed it. I will un fix it. Sorry about that.

Sometimes there are spelling errors in titles and being an associate editor in another life, I naturally fix them.

[Nemo_imp]

really? That's my fault. I thought "Holy" was misspelled and it bothered me so I fixed it. I will un fix it. Sorry about that.

Sometimes there are spelling errors in titles and being an associate editor in another life, I naturally fix them.

Ha! I knew it!! It's how Robin (Chris O'Donnell) said it the first time in the horrible Batman Forever movie. "Holie rusted metal, Batman! It's full of holes." I don't know why I remember this stuff, I should use my memory space for useful things.

Nonetheless, thanks for watching out for my second language deficiencies.