The design of a dedicated microprocessor based data acquisition and analysis system is described, as applied in a dual processor diesel engine control system. This auxiliary processor performs the task of sampling available engine sensors and analyzing the data to extract information valuable as feedback to the main controller. Large quantities of data may be taken and analyzed in real time to provide support for more sophisticated and precise engine control strategies, without overloading the main control processor.Specialized hardware and software features are highlighted, which permit rapid data acquisition and analysis, and efficient interprocessor communications. Design issues associated with distributed processing architectures for engine control computers are discussed.A technique for determination of the actual injected fuel quantity from real-time analysis of the injector needle lift signal is suggested as a potential application for the auxiliary processor. This application makes possible true closed-loop fuel quantity control, with the potential for improvements in engine emissions and efficiency. Other possible applications are discussed in the context of more sophisticated control strategies.