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LESSON 3: POWERTRAIN
CMCV Block Diagram
The CMCVs are controlled electronically by the PCM.
•
The inputs used by the PCM for the CMCV operation are:
– Engine Speed
– Throttle Position
– Air Temperature
– Cylinder Head Temperature
•
The CMCV system does not use a feedback loop.
•
The CMCVs open at a predetermined engine speed.
– At higher RPM, they do not affect the intake air charge.
– Proper stoichiometric air/fuel ratio (14.7:1) is easiest to achieve when the intake air is moving quickly.
– CMCVs close to help the intake air charge move more quickly at low RPM
– When the opening is narrower, the air charge moves more quickly as it enters the combustion chamber
(Bernoulli’s Principle).
– Bernoulli’s Principle states that when a given volume of air passes through a smaller passage, it will cause
the air to speed up.
2005 Expedition/Navigator New Model Technician Training02-SEP-043-10