High Altitude - Lower Octane Gas?
#21
03-02-2011, 06:00 AM
That wasn't a result of the fuel. You lose about 25% of your power at Denver altitude due to the loss of oxygen in the atmosphere.
You can get away with lower octanes at altitude because of the lower cylinder pressure. I wouldn't be too afraid of backing it down one octane grade, but I'd also log data with a calibration tool to be safe.
You can get away with lower octanes at altitude because of the lower cylinder pressure. I wouldn't be too afraid of backing it down one octane grade, but I'd also log data with a calibration tool to be safe.
#22
03-02-2011, 06:35 AM
Thank you!
Finally someone speaks the truth!
"Premium" isn't "best".
Here's a brain bender, "high" octane is actually lower in actual "'octane". To simplify, The rated number is a reference of lack of octane...not an increase...
Marketing! magic isn't it?
"Premium" isn't "best".
Here's a brain bender, "high" octane is actually lower in actual "'octane". To simplify, The rated number is a reference of lack of octane...not an increase...
Marketing! magic isn't it?
There is no such thing as "premium" gasoline. It is a marketing thing. All gas has the same BTU's which is where the power comes from in an internal combustion engine.
Octane is simply a measurement unit of a blend of gasoline to resist ignition.
The power comes from the gas expansion when ignited. So the cooler the incoming charge the more expansion. The fuller the amount of fuel burned increases the expansion. No gas burns completely and the unburned goes out the exhaust port. The lower the octane the more fully it burns. There are some riders who are very alert have noticed that lower octane gas in their air cooled engines runs hotter. It will also provide a slight uptick in mpg.
87 octane will start better. Old school mechanics back in the 50's to 70's before FI would run lower octane in the winter for better starting. They would also retard the spark some.
The higher the octane the more goes out the pipe unburned.
91 octane for a HD is the "recommended" gas to use. The ECM will allow the use of 87 octane not because HD wants to but because they are required to by the government.
If you try to go from Denver up to the Eisenhower Tunnel at about 12,000 feet elevation with 93 octane you will be blowing huge black smoke and your bike would stall at idle.
Again power is the expansion of hot gasses not octane.
Octane is simply a measurement unit of a blend of gasoline to resist ignition.
The power comes from the gas expansion when ignited. So the cooler the incoming charge the more expansion. The fuller the amount of fuel burned increases the expansion. No gas burns completely and the unburned goes out the exhaust port. The lower the octane the more fully it burns. There are some riders who are very alert have noticed that lower octane gas in their air cooled engines runs hotter. It will also provide a slight uptick in mpg.
87 octane will start better. Old school mechanics back in the 50's to 70's before FI would run lower octane in the winter for better starting. They would also retard the spark some.
The higher the octane the more goes out the pipe unburned.
91 octane for a HD is the "recommended" gas to use. The ECM will allow the use of 87 octane not because HD wants to but because they are required to by the government.
If you try to go from Denver up to the Eisenhower Tunnel at about 12,000 feet elevation with 93 octane you will be blowing huge black smoke and your bike would stall at idle.
Again power is the expansion of hot gasses not octane.
#23
03-02-2011, 09:07 AM
There is no such thing as "premium" gasoline. It is a marketing thing. All gas has the same BTU's which is where the power comes from in an internal combustion engine.
Octane is simply a measurement unit of a blend of gasoline to resist ignition.
The power comes from the gas expansion when ignited. So the cooler the incoming charge the more expansion. The fuller the amount of fuel burned increases the expansion. No gas burns completely and the unburned goes out the exhaust port. The lower the octane the more fully it burns. There are some riders who are very alert have noticed that lower octane gas in their air cooled engines runs hotter. It will also provide a slight uptick in mpg.
87 octane will start better. Old school mechanics back in the 50's to 70's before FI would run lower octane in the winter for better starting. They would also retard the spark some.
The higher the octane the more goes out the pipe unburned.
91 octane for a HD is the "recommended" gas to use. The ECM will allow the use of 87 octane not because HD wants to but because they are required to by the government.
If you try to go from Denver up to the Eisenhower Tunnel at about 12,000 feet elevation with 93 octane you will be blowing huge black smoke and your bike would stall at idle.
Again power is the expansion of hot gasses not octane.
Octane is simply a measurement unit of a blend of gasoline to resist ignition.
The power comes from the gas expansion when ignited. So the cooler the incoming charge the more expansion. The fuller the amount of fuel burned increases the expansion. No gas burns completely and the unburned goes out the exhaust port. The lower the octane the more fully it burns. There are some riders who are very alert have noticed that lower octane gas in their air cooled engines runs hotter. It will also provide a slight uptick in mpg.
87 octane will start better. Old school mechanics back in the 50's to 70's before FI would run lower octane in the winter for better starting. They would also retard the spark some.
The higher the octane the more goes out the pipe unburned.
91 octane for a HD is the "recommended" gas to use. The ECM will allow the use of 87 octane not because HD wants to but because they are required to by the government.
If you try to go from Denver up to the Eisenhower Tunnel at about 12,000 feet elevation with 93 octane you will be blowing huge black smoke and your bike would stall at idle.
Again power is the expansion of hot gasses not octane.
#24
08-04-2023, 07:09 PM
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#25
08-04-2023, 07:32 PM
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#26
08-04-2023, 08:01 PM
Road Master
I have started carrying a bottle of Amsoil motorcycle octane boost in case I can't find a station with 91 or better. Yes, I live near Denver. Yes altitude suck for power (-20 to 24% depending on the weather), it also will mess with your tire pressures. If you have correct pressures at sea level, they will read high up here. When I go down toward sea level, I have to add air to the tires. My Camaro and my wife's Jeep require 91 or better. Will they run on lower octane, yes. But they both have knock sensors in the engine and the computer will pull timing if even the slightest knock if detected and the resulting power loss is noticeable. Yes, they do get knock retard on lower octane fuel even up here. The bike does not have knock sensors (to my knowledge), so I just run the 91 to be safe.
Last edited by Black Ultra; 08-04-2023 at 08:02 PM.
#27
08-05-2023, 10:12 AM
Not a Moderator!
I have started carrying a bottle of Amsoil motorcycle octane boost in case I can't find a station with 91 or better. Yes, I live near Denver. Yes altitude suck for power (-20 to 24% depending on the weather), it also will mess with your tire pressures. If you have correct pressures at sea level, they will read high up here. When I go down toward sea level, I have to add air to the tires. My Camaro and my wife's Jeep require 91 or better. Will they run on lower octane, yes. But they both have knock sensors in the engine and the computer will pull timing if even the slightest knock if detected and the resulting power loss is noticeable. Yes, they do get knock retard on lower octane fuel even up here. The bike does not have knock sensors (to my knowledge), so I just run the 91 to be safe.
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bmaier (08-05-2023)
#28
08-05-2023, 10:27 AM
#29
08-05-2023, 11:43 AM
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