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In a modern small gasoline engine fuel injection system, the load of the engine is estimated based on the measurement of the manifold absolute pressure (MAP) sensor, which took place in the intake manifold. This paper present a more economical approach on estimating the MAP by using only the measurements of the throttle position and engine speed, resulting in lower implementation cost. The estimation was done via two-stage multilayer feed-forward neural network by combining Levenberg-Marquardt (LM) algorithm, Bayesian Regularization (BR) algorithm and Particle Swarm Optimization (PSO) algorithm. Based on the results found in 20 runs, the second variant of the hybrid algorithm yields a better network performance than the first variant of hybrid algorithm, LM, LM with BR and PSO by estimating the MAP closely to the simulated MAP values. By using a valid experimental training data, the estimator network that trained with the second variant of the hybrid algorithm showed the best performance among other algorithms when used in an actual retrofit fuel injection system (RFIS). The performance of the estimator was also validated in steady-state and transient condition by showing a closer MAP estimation to the actual value. [ABSTRACT FROM AUTHOR]

Abstract: Most motorcycles in developing countries use carburettors as the fuel delivery system especially for models with cubic capacity of less than 350cc. However, small gasoline carburetted engines suffer from low operating efficiency, high fuel consumption and produce high level of hazardous emissions. A retrofit fuel injection system (FIS) is a system that is developed to totally replace the conventional carburettor system to improve its fuel economy and exhaust emissions, providing a low-cost alternative in an effort to reduce fuel costs and air pollution. This paper provides a comprehensive review on the retrofit fuel injection technology developed for small gasoline spark ignition (SI) motorcycle engines from 50cc to 350cc. Three main retrofit FIS schemes – the throttle body injection (TBI), port fuel injection (PFI) and direct injection (DI) – are compared, in terms of configurations, complexity, costs and performances. [Copyright &y& Elsevier]