An On-Board Distillation System to Reduce Cold-Start Hydrocarbon Emissions

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. The OBDS fuel used throughout the test program was derived from certification gasoline.

The key benefits provided by the OBDS fuel were (1) emissions reductions over the FTP drive cycle of >50% for hydrocarbons and ≈73% for CO, (2) decrease in catalyst light-off time >50%.