Increasingly high demands on pollutant control on automotive engines have
been pushing the level of sophistication of engine control modules higher and
higher. In this context, explain the need for closed-loop control in automotive
engines. Typically, for closed-loop control of spark ignition (SI) engines, the
air-fuel ratio is used as feedback parameter, which is measured by the zirconia
based oxygen sensor. Oxygen sensors used in SI engines have limited performance during engine transients. It is proposed to use the cylinder pressure-based
parameter as a feedback parameter. Explain and discuss the air-fuel ratio
estimation method using suitable equations and schematics from the following
inputs.
(a) Measured crank angle-based in-cylinder pressure data over an engine cycle.
(b) Calculated crank angle-based heat release data over an engine cycle.
(c) Measured exhaust gas species.