Flextube catalyst performance in 4-stroke motorcycle exhaust systems

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Flextube catalyst performance in 4-stroke motorcycle exhaust systems

Larkin, M.P. / Dettling, J.C. / Galligan, M.P.

An analysis of 4-stroke motorcycle emission systems indicates that a heat tube has the potential for meeting the regulatory standards if the location in the exhaust pipe matches the specific operating temperature requirements of the device. The location of a heat tube is determined by the diameter and shape of the exhaust pipe. Since the exhaust flowrate and temperature across the catalytic device determine its effectiveness, it is suggested that a flexible catalyzed tube, which could be placed anywhere in the exhaust, would have a greater potential than a rigid heat tube for solving a wide range of emission application needs. To maximize the benefit from such a simple, cost-effective device, application of the 'flex-tube catalyst' was studied over a wide range of conditions. A test matrix that used high and low levels of Pt/Rh ratio and tube diameter was used to study 'flex-tube catalyst' performance in 4-stroke motorcycle exhaust systems. Engine variables include inlet temperature, AFR, exhaust flow and backpressure. Catalyst variables that were probed included tube diameter, precious metal ratio, and rigid or Flextube(TM) design. Data will be presented to show the benefits of such a device in various configurations. Performance is assessed by comparing the conversion of pollutants at various temperatures and flowrates.