Connecting to coil packs, or "coil on plug" ignition systems
Most modern ignition systems come in one of the following forms:
- A “remote” coil pack and short HT leads to the spark plugs:
- The coils are mounted directly on the spark plugs:
In the case of a remote coil pack there are two options: - we can either get a signal from the HT lead using a clip on pickup, or we can get a signal from the coil feed.
When the coil is mounted directly on the spark plug, there is no practical way to get a signal from the HT side - the only way is to connect it to the coil side. For both a “remote” coil pack or a “plug mounted” coil pack there are two types available and it is important to know which you are using, as it will affect the way that the RPM feed is connected up.
- The “drive” electronics can be built into the coil itself. In this case the coil has a high power 12v feed, a ground connection (although this might be via the chassis or engine) and a signal from the ECU. The signal from the ECU to the coil is only a low power signal, typically 5v or 12v pulses. This type of signal is suitable for connection to the “low level” RPM input on the DL1.
- The “drive” electronics are built into the ECU (or possibly the ignition box). In this case the coil typically has a high power 12v feed, and the other end of the coil is grounded by a high power driver in the ECU. In this case the signal from the ECU to the coil is a high power signal and will have very high voltage spikes on it. This type of signal must not be connected to the low level input on a DL1, as the large voltage spikes with permanently damage the unit!! This type of signal must be connected to the high level input.