Altitude Compensation

[David M Parrish]

> From:          cloud at peaches.ph.utexas.edu (tom cloud)

> mountains, you have to change the jets. Barometric pressure (BAP / MAP)
> doesn't tell you either.  I would think the EGO would tell you (albeit a

Actually, MAP can. MAP is an absolute pressure, so as you go up, the 
manafold pressure will also drop without changing the throttle. 
Combine MAP with temperature and the engine's volumetric efficiency, 
you can get a pretty good idea about the actual mass flow of air.

> quantity of O2 available can be adequately determined from the volume
> of air flow (MAF) and density (BAP or MAP).  If one doesn't have MAF,

MAF will do it by itself. How much fuel you squirt is based squarely 
on the mass of oxygen in the cylinder and that's exactly what a MAF 
tells you. MAP+temp+VE+fancy math gives you about the same thing.

---
David Parrish
I don't even want to think about humidity...