Re: [VAC] Re: [VACEngine Performance

[Darrell Kachilla <drk@xxxxxxxxxxxxxxxxxx>]

BASIC CAUSE:

the amount of oxygen in the air is much less at altitude than at sea level,
and you need so many pounds of oxygen to burn so many pounds of fuel
(ie - about 15:1 for gasoline)
in that engine pulling the load.

DISCUSSION

unless you have a turbocharger, 
or a good computer controlled fuel injection using the oxygen sensors,
the air:fuel ratio being burned in your cylinders
will alter drastically when you change several thousand feet:
your engine starts to lean out as you go up,
and enrichen as you go down - 
power produced falls off from the ideal mix.

your body reacts the same way, 
as flatlanders discover after taking a short hike in the mountains :-)


fuels have different octanes, and now are even tuned for different
regions,temperatures, and perhaps altitude.  
This changes the burn characteristics, 
and has oxygen  assistors added sometimes, 
ostensibly to promote better emission control.


small airplanes have a special control to control this air-fuel mixture;
cars don't.  
In olden days the manual choke would help when going up in altitude.

darrell