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Powertrain and vehicle technology is rapidly changing to meet the ever increasing demands of customers and government regulations. In some cases technologies that are designed to improve one attribute may impact others or interact with other design decisions in unexpected ways. Understanding the interactions and optimizing the transient performance at the vehicle level may require controls and calibration that is not available until late in the vehicle development process, after hardware changes are no longer possible. As a result, an efficient, up front, CAE process for assessing the interaction of various design choices on transient vehicle behavior is desirable. Building, calibrating and validating a vehicle system model with full controls and a mature calibration is very time consuming and often requires significant experimental data that is not available until it is too late to make hardware changes.

Good air/fuel ratio (A/F) control is essential to high quality combustion performance, drivability and emissions in internal combustion engine powered vehicles. Cold start and transient fuel wall wetting effects cause significant A/F control challenges in port fuel injected (PFI) engines. Transient fuel compensation (TFC) strategies are used to help control the A/F during cold starts and transient load and RPM conditions for good vehicle performance, but developing optimum TFC strategies and calibrations in a vehicle with many competing effects is very difficult. Thus, simplified transient tests such as fuel or throttle perturbation tests are often used to develop and validate new strategies or calibrations for use in vehicle. This paper will illustrate the use of a validated physical model to analytically assess the value of fuel and throttle perturbation tests for developing a TFC calibration for vehicle use.

The On-Board Distillation System (OBDS) extracts, from gasoline, a highly volatile crank fuel that enables simultaneous reduction of start-up fuel enrichment and significant ignition timing retard during cold-starting. In a previous paper we reported reductions in catalyst light-off time of >50% and THC emissions reductions >50% over Phase I of the FTP drive cycle. The research presented herein is a further development of the OBDS concept. For this work, OBDS was improved to yield higher-quality start-up fuel. The PCM calibration was changed as well, in order to improve the response to intake manifold pressure transients. The test vehicle was tested over the 3-phase FTP, with exhaust gases speciated to determine NMOG and exhaust toxics emissions. Also, the effectiveness of OBDS at generating a suitable starting fuel from a high driveability index test gasoline was evaluated.

An On-Board Distillation System (OBDS) was developed to extract, from gasoline, a highly volatile crank fuel that allows the reduction of startup fuel enrichment and significant spark retard during cold starts and warm-up. This OBDS was installed on a 2001 Lincoln Navigator to explore the emissions reductions possible on a large vehicle with a large-displacement engine. The fuel and spark calibration of the PCM were modified to exploit the benefits of the OBDS startup fuel. Three series of tests were performed: (1) measurement of the OBDS fuel composition and distillation curve per ASTM D86, (2) measurement of real-time cold start (20 °C) tailpipe hydrocarbon emissions for the first 20 seconds of engine operation, and (3) FTP drive cycles at 20 °C with engine-out and tailpipe emissions of gas-phase species measured each second. Baseline tests were performed using stock PCM calibrations and certification gasoline.