Fitting directly to the ignition coil
The red sensor lead for the rpm pickup can be fitted directly to the low-tension side of an ignition coil. To do this, it must be fitted to the "–" terminal on the coil.
Wires with ring terminals
Red Wire - Connects to the P clip The P Clip must go around one of the HT leads which go from the distributor, or coil pack, to the spark plugs. The P clip should fit well around the lead without squashing it.
Black Wire - This is the signal ground and must connect to the engine
A good connection to the engine ground is required. Ideally this should use an existing bolt which is long enough to support the ring terminal. If this is not possible, the ring terminal can be attached to the vehicle body (negative earth cars only).
- This method can only work when there is a spark to detect. Depending on how the coil is driven (mechanical points or ECU etc) the ignition maybe cut by a rev limiter system, traction control or when the engine is on over-run. If the ignition is cut you will get "straight lines" on the RPM graphs
- Again, depending on how the coil is driven the dwell time of the coil will change with engine speed and engine load. The longer the dwell time, the more power there is in the spark and the easier it is to detect. To make sure that you have a reliable RPM signal 100% of the time, you will need to test it over a variety of speed and load conditions