| 摘要 |
<p>A method of detecting degradation of a cam profile switching system in an internal combustion engine 10, comprising operating the engine 10 in one condition of the cam profile switching system and providing for a first cylinder subset, or cylinder bank 11,12, the inlet fuel flow and the corresponding oxygen content of the exhaust flow, measured by lambda sensors 22,23, and calculating the mass of air passing through the first cylinder subset in a defined time period, and also providing the same for a second cylinder subset, and comparing the mass air flows of each cylinder subset to give a standard ratio. Momentarily forcing the cam switching system of just one of the cylinder subsets to an alternative condition and re-calculating the mass of air passing through the subsets and then re-calculating a revised ratio and comparing the standard ratio and the revised ratio, wherein a significant change of air flow ratio will indicate that there is no fault in the cam profile switching system.</p> |
