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Technical Paper

Model Based Diagnosis of Leaks in the Air Intake System of an SI-Engine

1998-02-23
980514
One important area of SI-engine diagnosis is the diagnosis of leakage in the air-intake system. This is because a leakage can cause increased emissions and drivability problems. A method for accurately detecting leaks is presented. The results are developed for a turbo-charged engine but they are also valid for a naturally aspirated SI-engine. The method is based on a physical model of the leaks and includes an estimation of leakage area. By knowing the area, it is possible to reconfigure the control algorithm such that, the effect of the leak on emissions, is suppressed. As small leaks as 2 mm in diameter can be detected and it is possible to distinguish between leakages before or after the throttle. The method is suitable for on-line implementation.
Technical Paper

Ignition Control by Ionization Current Interpretation

1996-02-01
960045
Spark advance setting in spark-ignited engines is used to place the in-cylinder pressure curve relative to the top dead center. It is demonstrated that ionization current interpretation is feasible to use for spark advance control to optimize engine performance. A feedback scheme, not a calibration scheme, based on ionization current is proposed. It is thus related to pressure sensor feedback schemes, that have reported good results, but have not yet proven cost effective due to the cost of the pressure sensor. The method proposed here is very cost effective since it uses exactly the same hardware and instrumentation (already used in production cars) that is used to utilize the spark plug as a sensor to detect misfire and as a sensor for knock control. The only addition for ignition control is further signal interpretation in the electronic engine control unit. A key idea in our method is to use parameterized functions to describe the ionization current.
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