from the Bing Agency the best place to get Bing parts in North America) Manual:
"From sea-level to about 3,000 feet elevation, atmospheric pressure decreases about one-inch-per-thousand feet of altitude-therefore our 29.92 barometer reading at sea-level now becomes about 27. At 5,000 feet, about 25, and 20.6 at 10,000 feet. Our engine (and carburetor) only react to air velocity-not weight of air. Not knowing this, the carburetor continues flowing the same amount (by weight) of fuel, and all of a sudden our "ideal mixture" at sea-level becomes extremely rich at higher elevations. The Bing carburetor is less susceptible to changes in elevation than other carburettors in use, and in general does not require jetting changes for the idle and lower part-throttle settings. These settings can be compensated for by mixture screw adjustment. However, the upper part-throttle range will require the lowering of the jet needle to lean out mixture and continuous operation at higher elevation certainly necessitates the changing of the main jet. The table provides all information necesssary to determine jetting changes in relation to altitude changes.
Altitude in feet |
Temp (F) | 0 | 1,600 | 3,300 | 5,000 | 6,500 | 8,200 | 10,000 | 11,500 | 13,000 |
-22 | 104 | 103 | 101 | 100 | 98 | 97 | 95 | 94 | 93 |
- 4 | 103 | 102 | 100 | 99 | 97 | 96 | 95 | 93 | 92 |
+14 | 102 | 101 | 99 | 98 | 96 | 95 | 94 | 92 | 91 |
+32 | 101 | 100 | 98 | 97 | 95 | 94 | 93 | 91 | 90 |
+50 | 100 | 99 | 97 | 96 | 95 | 93 | 92 | 91 | 89 |
+59 | 100 | 99 | 97 | 96 | 94 | 93 | 92 | 90 | 89 |
+68 | 100 | 98 | 97 | 95 | 94 | 93 | 91 | 90 | 88 |
+86 | 99 | 97 | 96 | 94 | 93 | 92 | 90 | 89 | 88 |
+104 | 98 | 96 | 95 | 94 | 92 | 91 | 90 | 88 | 87 |
+122 | 97 | 96 | 94 | 93 | 92 | 90 | 89 | 88 | 86 |
EXAMPLE: You're going to do a lot of touring in Colorado (Elevation about 5,000 feet). Your machine is performing just fine in Galveston, Texas (Elevation 7 feet). Your main jet is size 150. Temperature in Galveston (86 degrees F)-Denver (50 degrees F). The new jet required to obtain the same mixture ratio as was provided by the size 150 is determined from the equation:
J2= A2/A1 X J1
Where:
A2 = the second altitude (Colorado)
A1 = the first altitude (Galveston)
J1 = original main jet (150)
A2 = 96 (alt 5,000-temp. 50 deg.)
A1 - 99 (alt "0"-temp 86 deg.)
J1 - 150 (original main jet)
J2 =96/99 x 150 or, .97 x 150 = 145
Therefore, the same mixture at sea-level with a 150 main jet will be achieved at 5,000 feet with a 145 main jet (AT ABOVE TEMPERATURES ONLY)
If temperature in Colorado was 86 degrees, we would have:
J2 = 94/99 x 150 = .95 x 150 = 142
When changing jets for altitude, always make correction for temperature as well."
Effect of Altitude on Horsepower,
by Tom Vervaeke
(Doing some research) ..."on the effects of elevation on available horsepower. I did a quick web search and found the following HP calculator.
I did a few runs using the factors below. I only changed the altitude after each calculation.
Constants I used:
----------------
Air Temp: 80 F (median for us in summer)
Barometric Pressure: 29.96 (standard)
Dew Point: 50 F (about normal for Colorado)
Elevation in Feet | Relative HP |
0 | 101.2% |
500 | 99.0% |
1000 | 96.9% |
2000 | 92.8% |
3000 | 88.8% |
4000 | 85.1% |
5000 | 81.4% |
6000 | 78.0% |
7000 | 74.6% |
8000 | 71.4% |
9000 | 68.4% |
10000 | 65.4% |
11000 | 62.6% |
12000 | 59.9% |
13000 | 57.2% |
14000 | 54.7% |
So, on average, around town in Denver I've got about 81.4% of the HP someone at sea level would have. On top of Mt. Evans (14,000') you only have about 54.7% of the available HP. Typical mountain riding in the 8000-10,000' range shows us with a 30-35% loss. About what I'd guess. I have no idea on how accurate this calculator is but at a first glance it seems about right.
, Colorado, USA"
Editors note - I think this is roughly valid, ASSUMING that the jetting is corrected for each altitude as well. If you don't change anything and go from properly jetted at sea level straight to 14,000 feet, the loss will be even greater. EFI bikes should be pretty close to this as the injection system should compensate. The R1100GS for instance works quite well at altitude without any changes.
I will try and get around to doing a metric version one day...I promise...
