Reduced Cold-Start Emissions Using Rapid Exhaust Port Oxidation (REPO) in a Spark-Ignition Engine 970264

An emissions reduction strategy was developed and demonstrated to significantly reduce cold-start hydrocarbon (HC) and CO emissions from a spark ignition (SI), gasoline-fueled engine. This strategy involved cold-starting the engine with an ultra-fuel rich calibration, while metering near-stoichiometric fractions of air directly into the exhaust ports. Using this approach, exhaust constituents spontaneously ignited at the exhaust ports and burned into the exhaust manifold and exhaust pipe leading to the catalytic converter. The resulting exotherm accelerated catalyst heating and significantly decreased light-off time following a cold-start on the FTP-75 with a Ford Escort equipped with a 1.9L engine. Mass emissions measurements acquired during the first 70 seconds of the FTP-75 revealed total-HC and CO reductions of 68 and 50 percent, respectively, when compared to baseline measurements. These reductions were realized through a) rapid exhaust system heating which reduced the catalyst light-off time from 45 seconds to less than 15 seconds for HC, and b) the consumption of pre-catalyst HC and CO emissions in the rapid exhaust port oxidation (REPO) process.