| 摘要 |
A method (120) and apparatus (52) are disclosed for controlling ignition timing during startup of a two-stroke internal combustion engine (30) while avoiding ignition timing errors caused by engine speed fluctuations. A rotational component (58) of the engine (30), such as a flywheel, bears a plurality of spaced indicator markers (1-24, A-C) including a plurality of ignition triggering markers, each of which designates a position on the rotational component (58) that is acceptable for triggering ignition in a respective cylinder of the engine. Ignition in each cylinder is triggered upon detecting (124, 126) the associated ignition triggering marker and without taking engine velocity into account. Ignition timing errors that could otherwise be introduced due to erroneous assumptions based on engine speed therefore are avoided. In order to optimize performance and reduce emissions after engine startup, the engine preferably incorporates measures to determine when a calculated engine velocity (130) exceeds a threshold engine velocity (132) and to change over (138) to an ignition control scheme that takes calculated engine velocity into account after the calculated engine velocity exceeds the threshold engine velocity. The threshold engine velocity preferably is one that at least approaches a minimum idle speed of the engine. In the case of a 95-135 hp V-4 engine, the threshold velocity preferably is on the order 300 rpm to 400 rpm. The method (120) is particularly beneficial in engines (30) having less than six cylinders because those engines exhibit the most dramatic pressure and speed fluctuations during engine startup. |
