Altitude Compensation

[Mark Pitts]

The point is even tho' the density drops, if you compress that air to =
sea level density, there is less oxygen in it, thus you need to lean out =
at altitude.

Sorry to go back to my model airplanes, but for the glider tugs (which =
ran 120cc petrol engines, with electronic ignition) we had to solder an =
arm on the end of the needle so that we could fit a servo and adjust =
mixture in flight, otherwise we lost so much power, we couldnt pull the =
glider any higher. And we are only talking 5000' Like a mile or so up!

At ground level the tugs would climb out at about 45 degrees, with =
anything on the back..

Mark


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From:  David M Parrish[SMTP:dmp at bmesun1.MCG.EDU]
Sent:  Wednesday, September 11, 1996 6:36 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  Re: Altitude Compensation

> From:          "Robert J. Harris" <bob at bobthecomputerguy.com>

> Does anyone do any altitude compensation?  Because, as altitude
> increases, not only does the air mass density decrease, but the
> percentage of oxygen decreases (simple physics - check books
> before questioning or flaming) and the oxygen decrease is independent
> of the density decrease. =20

Okay. I'll bite. What's your source for this simple physics?=20
(Remember Brownian motion and diffusion.)

On cars with MAF sensors, it's automatic, since you're measuring=20
the Mass of air and X mass of air needs Y mass of fuel.

Speed density systems measure pressure and temperature to calculate=20
the mass.

---
David Parrish
Carbs and aircraft injection are a whole 'nuther ballpark.