Figure 1 Two-Stroke Catalyst Durability Over the Indian Drive Cycle (ref. SAE Paper 2001-01-0003)
HC Conversion% CO Conversion%
10 15 Distance '000 km
Four-stroke engine durability for motorcycles under similar aging and test evaluation conditions is expected to be as good or even better than that demonstrated in Figure 1 for two- stroke engines for the reason that lower engine-out emissions are associated with four-stroke engines and also because four-stroke engines have more advanced engine designs and fuel metering control.
To meet rigorous durability requirements experienced in actual use, catalyst technology is subjected to demanding catalyst aging and physical integrity evaluations. These tests include on-road durability demonstrations, bench testing where the catalyst-equipped engines are operated at wide open throttle for 100 hours, and/or hot vibration physical integrity tests in which the catalyst housing is subjected to cold water quenching and over 100 G force of vibration over extended periods of time (typically in the range of 100 hours). These durability tests are many times more severe than the operating conditions that a motorcycle would typically experience even under the most extreme actual operating conditions.
September 17, 2002