Altitude compensation (Re: 286 Vindication)

Zublin, Bryan (SD-MS) BZUBLIN at gi.com
Tue Feb 20 21:51:53 GMT 1996


> That's what people do however you have to stop the engine and restart it
> at the top of the mountain before it corrects!
> Two sensors is the best method. Two absolute or one absolute and one
> differential is does not matter. (If you want to change altitude).

Isn't it true that for a speed density efi system with an _absolute_ MAP 
sensor, then altitude compensation is not needed?  For example, if you 
changed altitude, the barometric pressure changes, which changes the 
pressure in the manifold, which the MAP sensor directly measures. 
 Temperature (air density) compensation is still needed.

Now for a efi system using the "trap door" air flow meter, I believe 
altitude compensation is needed.  In addition to temperature  compensation.

Bryan Zublin
bzublin at gi.com



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