Federal exhaust emission standards

Table 1. Federal Exhaust Emission Standards for Conventionally Fueled Passenger Cars and Light Trucks, g/km...

Federal Exhaust Emission Standards for Passenger Cars (grams/mile)... 

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). 

Table 7. Federal Light-Duty Exhaust Emission Standards...

Table 12. Federal Heavy-Duty Truck Exhaust Emission Standards, g/(kWh) ...

In the United States, federal regulations require automobile manufacturers to certify that vehicles are ia compliance with exhaust emission standards when tested under specific test procedures. 

Photochemical smog also contains unbumed hydrocarbons and carbon monoxide, both of which come from the exhaust of automobile engines. These pollutants can be reduced or eliminated from the atmosphere in a variety of ways. Cleaner running engines and catalytic converters greatly reduce NO and hydrocarbon levels. Strict federal tailpipe emission standards are encouraging automobile manufacturers to develop new cars that are powered by electricity or alternative fuels such as natural gas. 

Test Procedure. To comply with emission standards, representative vehicles must be mn for 80,000 km (Appendix IV of the Federal Test Procedure (FTP)) (3). The first 6,400 km are considered a break-in portion. Exhaust emissions are measured each 8,000 km between approximately 6,400 and 80,000 km of accumulation and a deterioration factor (DF) of emissions is calculated. A DF of 1.15 for HC indicates that HC emissions increased by 15% between 6,400 and 80,000 km, and were within the 80,000 km standard. This DF is applied to the 6,400 km emission test data points for all other model variations of the family of vehicles represented by the 80,000 km durability car. 

A major challenge even for advanced diesel engines is the array of impending U.S. federal Tier 2 and California LEV II emissions standards. Work is ongoing to achieve these standards and to ensure that the exhaust after-treatment devices required will meet the necessary durability standards. Two things are certain Diesel fuel quality must improve dramatically, at least to the 2006 ultra low sulfur diesel requirements and preferably well beyond, and the cost of a Tier 2 Bin 5 or LEV II compliant diesel system will be substantial, rivaling the cost of hybrid electric gasoline fueled vehicle systems. 

---