Emission control, vehicle engine start emissions

K. H. Heilman, G. K. Piotrowski, and R. M. Schaefer, Start Catalyst Systems Employing Heated Catalyst Technology for Control of Emissions from Methanol-Fueled Vehicles, SAE 93082, Society of Automotive Engineers, Warrendale, Pa., 1993. 

As a result of atmospheric pollution levels that exceed the National Ambient Air Quality Standards (NAAQS) in many parts of the United States, both the federal government and the State of California have implemented standards for exhaust and evaporative emissions from new vehicles (see Exhaust control, AUTOMOTIVE). The first of these standards went into effect in 1968 and mandated that the vapors from the vehicle crankcase be routed back through the engine and burned. Since then, the standards have continued to grow stricter. Table 7 shows the federal exhaust emission standards and Table 8 shows the more stringent California standards. California has mandated that starting in 1998 a certain percentage of new vehicles sales must be zero emissions vehicles (ZEV). 

A catalytic converter cannot function immediately after the cold start of an engine at its light-ofF temperature (t5q)icaUy 620 K), the catalyst operates at 50% efficiency but during the 90-120 s lead time, exhaust emissions are not controlled. Several methods have been developed to counter this problem, e.g. electrical heating of the catalyst using power from the vehicle s battery. 

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