An Investigation into the Challenges of Achieving Future Legislative Limits over Euro III and WMTC Drive Cycles for Current State-of-the-Art Motorcycle Technologies

Motorcycle technologies will face increased challenges in the future, not only in terms of the emissions levels at Euro III which are much lower (at between a half to one third) than current levels, but also from the demands of future emission test cycles themselves which will be more severe, especially in respect to the ambient start requirements and the high speed elements of both the Euro III cycle and World Motorcycle Test Cycle (WMTC).

A representative selection of five larger capacity (> 600cc) ‘state of the art’ Euro II level motorcycles were tested over future Euro III and World Motorcycle Test Cycles. The tests highlighted that NOx control will be critical for future motorcycle technologies; the WMTC especially produces high NOx in relation to the higher rates of acceleration, higher maximum speed and more transient nature of the cycle than current cycles. HC and CO emissions were also significantly influenced by the ambient start requirements of future cycles.

A further phase of work evaluated the performance of three state-of-the-art catalyst technologies as a replacement for the production system on one of the motorcycles. Initial tests showed that catalyst performance for NOx control was not as expected, and therefore an investigation into varying air-fuel ratio (AFR) was undertaken. Relatively small changes in AFR were shown to have a significant effect on NOx conversion. A final optimised AFR and catalyst build was defined which allowed Euro III emissions levels to be achieved.