AMM Air Mass Meter

[C M Smith <cmsmith@domain.elided>]

Bosch LH Jetronic uses an Air Mass Meter (AMM) which describes exactly what 
it does. It is not a volume or flow meter. It automatically compensates for 
air density whether density is affected by temperature or by elevation, or 
even barometric pressure due to meteorolgical events, using the hotwire 
technology. The L Jetronic uses a flow meter which converts flow into 
volume and the ECU then adjusts for various aforesaid factors and comes up 
with an air mass calculation for the fule quantity calculation.

SAAB now uses an absolute barometric pressure sensor in the intake plenum 
on their Turbos which feeds the actual air mass number to the Trionic ECU 
by calculating the mass from the absolute barometric pressure (it has a 
pressure transducer on the intake plenum and an ambient barometric sensor I 
believe from which it deduces the absolute pressure in the manifold. This 
compensates for turbo boost, temperature, elevation, meteorological 
effects, and whatever else could affect the air being burned in the 
combustion chambers including from air leaks in or out of the plenum. Neato 
as we used to say years ago 9well some of us anyway)
Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner

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