Justin Posted September 11, 2009 Share Posted September 11, 2009 Is there a general rule of thumb for power loss (HP/Torque) based on altitude? My Busa was dyno'd in Denver (5500 FT), just curious about how much that would translate to at sea level. Not that it's a power monster, stock except PC3, Yosh TRC pipes and BMC filter, just curious. Quote Link to comment Share on other sites More sharing options...
Redbird Posted September 11, 2009 Share Posted September 11, 2009 Is there a general rule of thumb for power loss (HP/Torque) based on altitude? My Busa was dyno'd in Denver (5500 FT), just curious about how much that would translate to at sea level. Not that it's a power monster, stock except PC3, Yosh TRC pipes and BMC filter, just curious. Most dynos will correct for altitude, temp, humidity. Don't know the formula, but whenever you see "corrected" horsepower in an article/review, that's what they're talking about. A google search would probably get you the math, though I doubt it'll be as simple as a rule of thumb type thing. Quote Link to comment Share on other sites More sharing options...
Justin Posted September 11, 2009 Author Share Posted September 11, 2009 Is there a general rule of thumb for power loss (HP/Torque) based on altitude? My Busa was dyno'd in Denver (5500 FT), just curious about how much that would translate to at sea level. Not that it's a power monster, stock except PC3, Yosh TRC pipes and BMC filter, just curious. Most dynos will correct for altitude, temp, humidity. Don't know the formula, but whenever you see "corrected" horsepower in an article/review, that's what they're talking about. A google search would probably get you the math, though I doubt it'll be as simple as a rule of thumb type thing. Thanks, I think I figured it out. First readout on the slip is the "actual", second is the "corrected" if I am not mistaken. Quote Link to comment Share on other sites More sharing options...
tomek Posted September 12, 2009 Share Posted September 12, 2009 3% loss for every 1000 ft of elevation for normally aspirated engines.Now, that is theoretical formula that may,may not be accurate for particular engine,but that is another story. Quote Link to comment Share on other sites More sharing options...
EVLXX Posted September 12, 2009 Share Posted September 12, 2009 Divide whatever number you have as a max HP number buy 1.235 for a 5500 feet elevation correction factor. Basically at your altitude you have a 20% loss in power.... so if you bike was putting out a correted 180 HP, you're really only making about 145 HP. Now if you think that's bad.... At 12,000 feet your mighty 180 HP at sea level would be reduces to a floppy 114 HP, basically a 37% loss in power. Quote Link to comment Share on other sites More sharing options...
Justin Posted September 12, 2009 Author Share Posted September 12, 2009 Divide whatever number you have as a max HP number buy 1.235 for a 5500 feet elevation correction factor. Basically at your altitude you have a 20% loss in power.... so if you bike was putting out a correted 180 HP, you're really only making about 145 HP. Now if you think that's bad.... At 12,000 feet your mighty 180 HP at sea level would be reduces to a floppy 114 HP, basically a 37% loss in power. Yeah, I knew it was something along those lines.. funny thing is when I first rode the XX out here from NY I really didn't "feel" a huge difference. Just goes to show you how rarely one actually uses every bit of HP a bike has. I even got the XX up to 178 indicated on highway 125 up by Walden once, and that's like 8000 ft. Surprised with that much power loss to get moving that fast (and yes, I'm aware that the actual speed was nowhere near the indicated). Quote Link to comment Share on other sites More sharing options...
Dotetcher Posted September 12, 2009 Share Posted September 12, 2009 Divide whatever number you have as a max HP number buy 1.235 for a 5500 feet elevation correction factor. Basically at your altitude you have a 20% loss in power.... so if you bike was putting out a correted 180 HP, you're really only making about 145 HP. Now if you think that's bad.... At 12,000 feet your mighty 180 HP at sea level would be reduces to a floppy 114 HP, basically a 37% loss in power. Yeah, I knew it was something along those lines.. funny thing is when I first rode the XX out here from NY I really didn't "feel" a huge difference. Just goes to show you how rarely one actually uses every bit of HP a bike has. I even got the XX up to 178 indicated on highway 125 up by Walden once, and that's like 8000 ft. Surprised with that much power loss to get moving that fast (and yes, I'm aware that the actual speed was nowhere near the indicated). I did notice the loss in power when I road in Colorado (from NY). I also noticed better gas mileage. Does that make sense? Quote Link to comment Share on other sites More sharing options...
tomek Posted September 13, 2009 Share Posted September 13, 2009 Divide whatever number you have as a max HP number buy 1.235 for a 5500 feet elevation correction factor. Basically at your altitude you have a 20% loss in power.... so if you bike was putting out a correted 180 HP, you're really only making about 145 HP. Now if you think that's bad.... At 12,000 feet your mighty 180 HP at sea level would be reduces to a floppy 114 HP, basically a 37% loss in power. Yeah, I knew it was something along those lines.. funny thing is when I first rode the XX out here from NY I really didn't "feel" a huge difference. Just goes to show you how rarely one actually uses every bit of HP a bike has. I even got the XX up to 178 indicated on highway 125 up by Walden once, and that's like 8000 ft. Surprised with that much power loss to get moving that fast (and yes, I'm aware that the actual speed was nowhere near the indicated). I did notice the loss in power when I road in Colorado (from NY). I also noticed better gas mileage. Does that make sense? Absolutely.Thinner air----> less aero drag-----> better fuel consumption.I typically get 10-15% better fuel consumption in CO. As far as loss of top speed,it is not as much noticeable as loss of acceleration because thinner air offers less aero drag.But the bike still weights the same. Typically airplanes are faster at higher altitude,up to the point. Quote Link to comment Share on other sites More sharing options...
Justin Posted September 13, 2009 Author Share Posted September 13, 2009 Absolutely.Thinner air----> less aero drag-----> better fuel consumption.I typically get 10-15% better fuel consumption in CO. As far as loss of top speed,it is not as much noticeable as loss of acceleration because thinner air offers less aero drag.But the bike still weights the same. Typically airplanes are faster at higher altitude,up to the point. Ahh, good point, did not consider that. So less air friction offsets the loss of power... Quote Link to comment Share on other sites More sharing options...
Iceman_40 Posted September 13, 2009 Share Posted September 13, 2009 Absolutely.Thinner air----> less aero drag-----> better fuel consumption.I typically get 10-15% better fuel consumption in CO. As far as loss of top speed,it is not as much noticeable as loss of acceleration because thinner air offers less aero drag.But the bike still weights the same. Typically airplanes are faster at higher altitude,up to the point. Ahh, good point, did not consider that. So less air friction offsets the loss of power... Most likely your engine didn't have as much O2 going in so it cut down the fuel going in. Otherwise it would run REAL rich. Don't think the drag would be that measurable. From 5500 feet to sea level I noticed a big diff when you jump on it, normal driving not so much. Quote Link to comment Share on other sites More sharing options...
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