Individual cylinder characteristic estimation for a spark injection engine

Engine control policies are mostly based on the assumption that all injectors have the same behavior independent of location and aging. In reality, injectors do vary and age. To contain variations around a nominal value, tight tolerances are imposed on the manufacturing process. Even if the manufacturing process is tightly controlled, the air-to-fuel (A/F) ratio needed to satisfy emission constraints is difficult to achieve due to aging and even slight mismatch among different injectors. To devise control policies that take into account behavior differences among injectors, we need to estimate injector characteristics from measurements that are taken on the engine during its life time. In this paper, we present an estimation technique for injector characteristics based on a set of measurements that can be carried out using the sensors present in the car, i.e., intake manifold pressure, crank-shaft speed, throttle-valve plate angle, injection timings and exhaust A/F ratio, which is measured by a single UEGO sensor placed at the exhaust pipe output.