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The progressive reduction in permissible tailpipe emissions levels from automobiles has been achieved through the adoption of ever more complex engine control systems and aftertreatment components. This, in turn, has resulted in the development of increasingly sophisticated monitoring systems that can detect the failure or gradual degradation of any of these components and thereby fulfill the requirements of the stringent On-Board Diagnostic (OBD) legislation. Traditional monitoring techniques involve a physical model approach, which describes the system under investigation. This approach has limitations, such as available knowledge base and computational load. Neural networks, on the other hand, have been recognized as a powerful tool for modeling systems which exhibit nonlinear relationships between measured variables, such as internal combustion engines.

Restricting the airflow to the engine is a convenient, and therefore common, method of regulating engine performance in many forms of motor sport. Formula SAE, and its European counterpart Formula Student, impose such restrictions on engine configuration. The capacity of the engines must not exceed 610cc but, more specifically to this study, the intake system must be fitted with a 20mm diameter restrictor through which all the air must pass. There are, however, a number of geometrical parameters which can be changed to maximise the performance of the restricted engine. In this study, the effects of modifying the restrictor design, intake runner length, intake camshaft profile, exhaust geometry, and silencer design were measured using a transient dynamometer. These tests were performed on a 600cc four-stroke, four-cylinder Yamaha YZF R6 engine.

The most common mode of deactivation suffered by catalysts fitted to two-stroke engines has traditionally been thermal degradation, or even meltdown, of the washcoat and substrate. The high temperatures experienced by these catalysts are caused by excessively high concentrations of HC and CO in the exhaust gas which are, in turn, caused by a rich AFR and the loss of neat fuel to the exhaust during the scavenging period. The effects of catalyst poisoning due to additives in the oil is often regarded as a secondary, or even negligible, deactivating mechanism in two-stroke catalysts and has therefore received little attention. However, with the introduction of direct in-cylinder fuel injection to some larger versions of this engine, the quantities of HC escaping to the exhaust can be reduced to levels similar to those found on four-stroke gasoline engines.