Comparison of two Exhaust Manifold Pressure Estimation Methods
In turbocharged engines with wastegate the exhaust
pressure can change rapidly. Two methods to estimate the exhaust
manifold pressure are compared for diagnosis of wastegate and
turbocharger of a spark-ignited engine. One relies on the first law of
thermodynamics and produces changes in exhaust manifold pressure. The
second uses a model of the mass of remaining exhaust gases in the
cylinder and results in absolute estimations of the exhaust manifold
pressure. They does not require any extra sensors in the exhaust
system after the calibration. Estimates of the exhaust manifold
pressure relies on information from an air-to-cylinder observer and a
static map. The exhaust manifold pressure estimators are compared
using a series of wastegate steps on a turbocharged SAAB 2.3 dm^3
SI-engine. The comparison showed that the method based on the first
law of thermodynamics was best suited for diagnosis purposes since it
was least sensitive to model errors.
Per Andersson
CCSSE,
2001

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