Postby Peter Clare » November 10th, 2014, 5:10 pm
Most 2 stroke twin cylinder petrol engines have both cylinders firing at the same time. You could therefore use two of these ignition units. one connected to cylinder 1 and 4 and the other connected to 2 and 3. two hall sensors and two magnets would be needed , one at. 30 degrees before top dead centre for no1 cylinder and the other at 30 degrees before top dead centre for no2 cylinder ( ie exactly 180 degrees apart).The magnets would need to be separated lengthwise on the crankshaft to avoid interference between them. The distance required could easily be checked by trial and error.
The fact that each cylinder would get a spark every revolution would not matter because the redundant spark would occur at the end of the exhaust stroke when there is nothing to ignite in the cylinder. Adjustment of the hall sensors either side of the 30 degree position should find optimum timing position - usually a bit retarded from max rpm available.