Design of NGK U3 Block Coils
U3 coils generally can be divided in two different groups.
- In this case, there is a dedicated ignition coil for each cylinder. An example for this technology is the U3010 type, used in smarts.
- It contains two independent coils. Each of them supplies one spark plug.
- In this case, there is only one coil which has two outputs and thus supplies two spark plugs simultaneously with one pulse of energy. This is called "wasted spark" or "double spark" technology.
An example is the U3001 Type, used by Fiat: