| Author | Message | ||
     Electraglider_1997 |
Where does the Uly get the best mpg? At higher altitudes or towards sea level? | ||
| Froggy |
Higher, I was on the Blue ridge parkway when I broke 75mpg. | ||
| J0hn0tt0 |
Holy christ! 75 MPG on a Uly?! | ||
| Froggy |
Its Uly-ish  I had about 210 miles on the tank, not even a flicker of the gas light so I filled up as soon as I could. I almost overfilled it, it took only about 2.8 gallons of gas. | ||
| Thetable |
I always get my best mileage on the BRP, but I think for me it has more to do with the pace than anything. | ||
| Froggy |
Ive ridden those speeds on local sea level roads, and don't get as good fuel economy. Optimal fuel economy based on my observations is about 45-50mph in 5th gear. | ||
| Johnnylunchbox |
Froggy, you forgot to mention that you were also inhaling some of the gas at that point when you got 75mpg.  | ||
| Hangetsu |
Hmm, I live at 5500 and I frequently ride day long stretches at 9000+ and I have yet to ever break 50 - ever. Must be the '09 curse. | ||
| Jcbikes |
I live in Colorado and as the snow melts in the higher mountains, i can ride up there (summer time of course). My mileage always goes up the higher rides I do. Yes, I have gotten 74 to 75 mpg many times in the last 4 years of owning the bike. 2004 XB12S Lightning. the higher you go, the air gets less so I guess the computer adjusts for this with less fuel. | ||
| Royintulsa |
Interesting question. When competing in aviation races, flying at lower altitudes results in better fuel economy and better air speeds. Horsepower and torque are always expressed in or adjusted for sea level and 60 degrees air temperature. The higher you go, the less power you make, the warmer it is, the less power you make. Also, it takes more runway and more fuel to take off at altitude. Altitude is your enemy when flying, except when you lose an engine, then you want all the altitude you can get to give you more glide time. Interesting question. | ||
| Ourdee |
Altitude is speed. I get my best mpg in the mountains going up and down the hills not just at one height. I got over 40 mpg for a tank of fuel in Colorado in a minivan. | ||
| Royintulsa |
Of the top ten factors effecting fuel mileage, altitude is number 9. 9. Altitude It may sound odd, but altitude does have a say in what kind of fuel economy your vehicle gets. There’s less oxygen at 10,000 ft than there is at sea level, meaning that for each stroke of your motor, your car takes in less oxygen, and thus produces less power. Less power means you’re more likely to get into the throttle and stay there—using more fuel than you normally would. Ha! I knew I was not crazy. | ||
| Itileman |
I'm now getting just over 50 mpg with an 09 XT riding at 3-6k feet. MPG is coming up as the engine gets broken in. Started out in the mid to high 30 mpg. Big improvement at 2k. | ||
| Garyz28 |
The best mileage can be obtained by starting at a high altitude then heading directly toward a lower altitude.  | ||
| Jb2607 |
08 ULY from NC. I live at 2500 feet and mileage is low 40's. I took bike out west and above 6500 feet I would be consistent mid 50's and often 60+, so based on my own personal observations, much better at high altitude. | ||
| Electraglider_1997 |
Here is what I infer from high altitude mpg spike: Our engines are capable of much better mpg than what they normally produce. High altitude air is less dense so the computer reduces gas to keep mixture correct. Less dense atmosphere also is easier for the bike to move through. Isn't that the reason that jets fly at high altitude because they become much more efficient in fuel usage? At high altitudes our engines get greater economy but at the expense of power (??). It would be nice if there was a handlebar button that could be switched on for high mpg highway droning. When the power was needed you could just switch back. Some bikes now come with just such a switch but not any Buells. | ||
| Thetable |
This is true for Carbs and the FI running in open loop, but if the system is running in closed loop, then it will adjust the fuel to stochiometric levels based on readings from the O2 sensor. | ||
| Arcticktm |
Don't forget that traffic and stops are one of the biggest killers of MPG. The Blue Ridge Pkwy is posted 45 mph mostly, and has very few places you ever have to stop or even slow down. I always get great mileage there. Moderate pace + no stops = killer MPG. I think that is a bigger factor than the altitude, though limiting how much power you can make will limit how much fuel you can burn if you are a throttle whacker! | ||
| Royintulsa |
quote: "This is true for Carbs and the FI running in open loop, but if the system is running in closed loop, then it will adjust the fuel to stochiometric levels based on readings from the O2 sensor." But you still have to have the air and fuel mixture close to the same ratio at high and low altitudes don't you? Electroglider, using high altitudes in aviation is mainly a safety factor, jumbo jets drop like a rock when they loose an engine and also to take advantage of tail winds. It usually takes one to two hours less to fly from Washington D.C. to London than London to D.C. In my Cessna I can glide for 20 minutes if I lose an engine at 7500 feet under normal conditions (and if I push any passengers out). A commercial airliner might last 6 minutes at 30,000 feet if they lost all power, but 45 minutes if they just lost one engine. | ||
| Road_kill |
I live at 200' above sea level. When I travel to North Georgia, 2-3000', my mpg increases ~5% (and I'm not easy on it). I believe the bikes and cars will always get better gas mileage at altitude assuming the same rpm, speed, and EFI (or CV) compensation to maintain similar A/F rations. Reason: the engine is running more efficiently at roughly the same output power. The throttle body will be more open resulting in a greater pressure ratio across the cylinder - making up the the reduced airflow. Higher pressure ratio + lower engine airflow = higher efficiency = lower fuel consumption. Oh yeah, lower drag in the thin air as well; though I'm not sure how much this will play given the low projected frontal area of the bike. As for aircraft: Jet engines are designed for peak operating efficiencies at the altitude they frequent the most. As such, large transports stink at short-haul routes and turboprops usually stay below 30k'. The Cessna I flew years ago had a natural limit to fuel efficiency vs altitude. It had a small engine with a fixed pitch prop. I always ran full open throttle at an altitude that met my needs for either speed (low) or range (high). To take advantage of even thinner air (low drag) at higher altitudes, I would have needed a larger displacement engine and a constant speed prop (turbo normalized would have been nice too). Nope, I was happy buzzing above the wheat fields of Kansas well under 10k' with the throttle full forward. | ||
| Tootal |
A CV type carb, as used on most Harleys and the old tube framers, used vacuum to raise the slide and needle. At elevation you produce less vacuum so it compensates for the thinner air resulting in better mileage. A closed loop injection system compensates by changing the AFV. Since the air is thinner your O2 sensors will notice you don't need as much fuel and will start giving you less which equals less power and better mileage. If you were running an old Weber side draft carb your exhaust would look like a diesel if you were jetted for sea level and took a ride up Pike's Peak! | ||
| Thunderbox |
There is no doubt that you get better mileage at altitude. You require less power to move through thinner air. Less power requirement means less fuel burnt and better mileage. | ||
| Crempel |
Here's another possible factor. Usually when riding at high altitude, you are riding up and down hills/mountains. Not always of course, but usually. My car has a instantaneous mileage computer that gives a nice idea of how this works. On a flat road at 75 mph I usually get about 23 mpg. Up a given hill this will drop to about 15 or so. This is a reduction of about 35%. If I turn around and go down the same hill the mileage will often increase to 45-50 mpg which is an increase of 95% or more. I don't expect this computer to be deadly accurate, but I'm sure its in the ballpark. So riding in hilly country should on average increase overall mileage, no? | ||
| Crempel |
Here's another possible factor. Usually when riding at high altitude, you are riding up and down hills/mountains. Not always of course, but usually. My car has a instantaneous mileage computer that gives a nice idea of how this works. On a flat road at 75 mph I usually get about 23 mpg. Up a given hill this will drop to about 15 or so. This is a reduction of about 35%. If I turn around and go down the same hill the mileage will often increase to 45-50 mpg which is an increase of 95% or more. I don't expect this computer to be deadly accurate, but I'm sure its in the ballpark. So riding in hilly country should on average increase overall mileage, no? |
