Engine Speed and position is read from a pattern of teeth on the crank. Most manufacturers patterns are already known such as Ford 36-1, Bosch 60-2, Rover (18-1 twice and late K series), Toyota 36-2 etc If using an engine without a crank trigger pattern, an external trigger wheel can be fitted. The trigger wheel is a general-purpose part and will require machining to fit the crank pulley with the crank position sensor mounted facing it.