Altitude and Power

[Punx Clever]

Thanks for all of the comments. I feel smarter already. 

If ECU makes adjustments for pressure and gets an indirect sense of airflow, does it just not adjust for airflow? Is that the reason it runs lean with less back pressure (aftermarket pipes) and increased airflow (cut or removed air box) and requires ECU adjustments, or PCIII, etc.?

Bingo! Not to mention being tuned lean to begin with to meet emissions...

[Fergus]

OK. I was kind of hoping that I was already running rich because of the altitude (same fuel, less o2) and I could modify the exhaust and air filter and not be too far off tune. But I was wrong  . I'll look at PCIII and/or ECU re-map.

Thanks again

[RUFKM]

This is not true.  Mountain climbers carry oxygen tanks to combat hypoxia because the percentage of oxygen in the atmosphere at high altitudes is in fact lower.

=fail.

The percentage of oxygen remains the same at sea level as it is at the top of Mt. Everest at about 20.8%.  The partial pressure of oxygen (the pressure exerted against lung tissue by the oxygen content alone) decreases below acceptable limits at extreme altitudes.  By using oxygen tanks climbers (or aviators) are increasing the partial pressure of oxygen against the lung tissue by having a higher oxygen content at the same (ambient) pressure.  The other alternative is to compress the existing air at altitudes to a pressure near that of sea level = pressurized cabin.


Please do the homework before you trash me again.

[NorDog]

=fail.

The percentage of oxygen remains the same at sea level as it is at the top of Mt. Everest at about 20.8%.  The partial pressure of oxygen (the pressure exerted against lung tissue by the oxygen content alone) decreases below acceptable limits at extreme altitudes.  By using oxygen tanks climbers (or aviators) are increasing the partial pressure of oxygen against the lung tissue by having a higher oxygen content at the same (ambient) pressure.  The other alternative is to compress the existing air at altitudes to a pressure near that of sea level = pressurized cabin.


Please do the homework before you trash me again.

Yeah, I already gave my mea culpa on this one.  Thanks for sharing though.

FTR, my mistake is worse than it appears.  I have professional training and experience by which i should know better.  Actually, I do know better.  The phrase "Terminal Brain Fart" comes to mind.



Great use of "fail" though.

[RUFKM]

Yeah, I already gave my mea culpa on this one.  Thanks for sharing though.

No worries NorDog.

Back to the 620 - if it's fuel injected and has an O2 sensor can Fergus run the FatDuc O2 Manipulator to adjust for his local conditions?  It's been great for many of us in adjusting the A/F ratio and at $86 delivered to my door it's by far the most cost-effective mod I've done.

[Holden]

Just for the record... but the %oxygen begins to decrease at an irrelevantly high altitude. Probably where the confusion came from.

The homosphere and heterosphere are defined by whether the atmospheric gases are well mixed. In the homosphere the chemical composition of the atmosphere does not depend on molecular weight because the gases are mixed by turbulence.[3] The homosphere includes the troposphere, stratosphere, and mesosphere. Above the turbopause at about 100 km (62 mi; 330,000 ft) (essentially corresponding to the mesopause), the composition varies with altitude. This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing. This allows the gases to stratify by molecular weight, with the heavier ones such as oxygen and nitrogen present only near the bottom of the heterosphere. The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.

[RUFKM]

yeah okay

i'll remember not to ride my make the beast with two backsin duc too muck over 330,000 feet for the risk of oxygen % decreasing

that's it i'm outa here or as i say RUFKM

[brad black]

i was going to type a lot to explain how it works, but just couldn't be bothered.  here's one i prepared earlier - http://www.bikeboy.org/fuelinjection.html

[ducpainter]

wow...

looks like some one got sensitive last night.

[NorDog]

wow...

looks like some one got sensitive last night.

Well, speaking only for myself, or rather, of myself, it seems that the most important case of low oxygen percentage around here lately has been the one in my brain.