03-01-2016, 09:58 AM
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.
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.