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The Honda Accord is the world's first automobile meeting the SULEV category criteria in the LEV-II exhaust emissions standards. An improved accuracy engine control system and catalyst account for the automobile's extremely low emissions. The accuracy engine control system includes double adaptive air-fuel ratio feedback loops composed of STR (Self-Tuning Regulator), for primary air-fuel ratio control, and PRISM (Prediction and Identification Sliding Mode Control), for secondary O2 feedback. The basic algorithm of the latter was presented at SAE 20001). However, two issues required further PRISM algorithm improvements in order to apply the double adaptive loops to an actual vehicle. One such achievement is both the compensation for engine dynamic characteristics by PRISM and the avoidance of the reciprocal interference with two adaptive loops.

The reduction of fuel consumption is of great importance to automobile manufacturers. As a prospective means to achieve fuel economy, lean burn is being investigated at various research organizations and automobile manufacturers and a number of studies on lean-burn technology have been reported to this date. This paper describes the development of a four-valve lean-burn engine; especially the improvement of the combustion, the development of an engine management system, and the achievement of vehicle test results. Major themes discussed in this paper are (1) the improvement of brake-specific fuel consumption under partial load conditions and the achievement of high output power by adopting an optimized swirl ratio and a variable-swirl system with a specially designed variable valve timing and lift mechanism, (2) the development of an air-fuel ratio control system, (3) the improvement of fuel economy as a vehicle and (4) an approach to satisfy the NOx emission standard.

In this research project, modeling of the dynamic air excess ratio (λ) behavior in the exhaust gas at the confluence point in the exhaust manifold was performed. By applying an observer which is one method described by modern control system theory, estimation of the λ for each cylinder was carried out using one λ sensor. The estimated value was used to perform λ feedback control for each cylinder, allowing compensation of deviation in air-fuel ratio between cylinders and individual control of fuel injection volume for each cylinder, dramatically enhancing λ controllability.

The purpose of this paper is to quantify the improvements possible for ULEV emissions by improved air-fuel ratio control during starting by modifying conventional fuel injection strategy with a first order wall-wetting-fuel model. Measurements of emissions during first 30 starting cycles of a ULEV engine, made with a fast response flame ionization detector (FID) and conventional fuel injection strategy, show that these account for 17% of the overall FTP-75 mode HC emissions. The wall-wetting-fuel model is a two coefficient model: α, the ratio of the injected fuel mass to the fuel mass inducted into the cylinder during a given cycle, and β, the ratio of the total fuel mass accumulated on the intake port wall to the mass inducted into the cylinder from the accumulated fuel at a given cycle.