A couple of altitude questions
#21
07-14-2013, 10:28 AM
Yes, lots of junk science here. The truth is simple and has been known since the 1920's. At sea level the air pressure is 14.5 psi. At 9000 ft elevation the air pressure is 10.5 psi. That means that at 9000 ft. the air intake of an engine is reduced by about 28%. So the engine's fuel injection system will reduce the fuel for each stroke by 28% to maintain the correct AFR. That means less fuel is used at any RPM. The compression psi is also reduced so lower octane is needed. What's the negative? Power is also reduced. Going up hills might take more throttle. But on level roads not so much. Result, better gas mileage. Planes fly at high altitudes for a reason. And it's not for the view. Check with ANY aircraft pilot, engineer, or mechanic. They'll say the same thing.
#22
07-14-2013, 11:12 AM
Extreme HDF Member
mileage should be about same under same conditions ( but for altitude) as controlled by the ECM.
variable could be less wind resistance, due to thinner air ( marginal), steady throttle hand, steady cruising speed(s) lower speeds than when running around home territory( wind resistance).
It takes about twice as much power to push the bike to 80 MPH as it does at 55 MPH
higher octane fuels do not "pack more power" or put a tiger in your tank. octane is a rating of the ability of the fuel to resist compression ignition ( like a diesel)
in fact a number of TX chains have been fined for selling 87 as premium...so who knows what you've been getting at home.
also ethanol content is a factor 10 to 15% ethanol gas gives reduced MPG by about 5%
maybe you have 15% ethanol at home, and the stations you stopped at didn't...pumps should be marked as to percentage of ethanol
so maybe some or all of the above.
unlikely: when the ecm senses pinging, it will retard ignition timing, which reduces MPG and power...could it be possible that the fuel you use at home has the ignition timing not as advanced as might be ?
mike
variable could be less wind resistance, due to thinner air ( marginal), steady throttle hand, steady cruising speed(s) lower speeds than when running around home territory( wind resistance).
It takes about twice as much power to push the bike to 80 MPH as it does at 55 MPH
higher octane fuels do not "pack more power" or put a tiger in your tank. octane is a rating of the ability of the fuel to resist compression ignition ( like a diesel)
in fact a number of TX chains have been fined for selling 87 as premium...so who knows what you've been getting at home.
also ethanol content is a factor 10 to 15% ethanol gas gives reduced MPG by about 5%
maybe you have 15% ethanol at home, and the stations you stopped at didn't...pumps should be marked as to percentage of ethanol
so maybe some or all of the above.
unlikely: when the ecm senses pinging, it will retard ignition timing, which reduces MPG and power...could it be possible that the fuel you use at home has the ignition timing not as advanced as might be ?
mike
#23
07-14-2013, 11:53 AM
Wow, talk about junk science. You do not recover as much energy going downhill as you expended going up the hill. If you could, you could just shut the engine off and coast over an indefinite number of equal size hills...
Less power is needed on a level surface than is needed going over hills.
The reason aircraft fly at such high altitudes (jet airliners) is the atmosphere is much thinner, which means much less drag, so less power is needed to push the plane. (I`ve spent the last 39 years as a jet engine mechanic).
Less power is needed on a level surface than is needed going over hills.
Planes fly at high altitudes for a reason. And it's not for the view. Check with ANY aircraft pilot, engineer, or mechanic. They'll say the same thing.
Last edited by Dan89FLSTC; 07-14-2013 at 12:01 PM.
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