Verification of long-term stability of emission control systems and some comments on different test methods 2001-24-0067
Since 1992 (for one vehicle since 1989) MTC has regularly performed emission tests on some vehicles equipped with closed-loop lambda-regulated Otto engines and catalysts. The vehicles are passenger cars of different kinds and emission control ""generations."" They are standard vehicles fulfilling Swedish A12 emission control limits, later on the EU emission limits. Some of them are also certified according to Swedish environmental class 1 and 2. The most advanced vehicle tested is certified according to US ULEV regulations. The vehicles with the highest mileage have been followed for more than 250,000 km with tests at yearly intervals. The vehicles were in the beginning tested according to the test cycle to which they were certified. Later on, other test cycles and steady-state tests were applied to the vehicles, as well as cold start tests at -7°C. Since 1994 all vehicles have been tested according to A12-14 test cycle (US test cycle), the 94/12/EC test cycle and the 98/69/EC (EU2000 or NEDC). Results are given for deterioration of emission at regulated test cycles. For some vehicles are constant speed emission reported. Since 1994 no leaded petrol has been delivered in Sweden by the oil companies. From 1997 and onwards lead concentration in Swedish petrol is below 0,1 μg/l. This means that deteriorated catalyst and lambda-sensor efficiency from 1994 and onwards is due to other factors than pollution of lead in unleaded petrol.