Abstract: The ignition unit includes a support housing containing two ignition coils each for the connection to at least one, and preferably two, associated spark plugs. Each ignition coil comprises a primary winding and a second winding disposed around the end arms of a magnetic core or circuit formed by only two packs of plates juxtaposed so that together they form essentially a figure-of-8 shape. The packs of plates are identical, essentially E-shaped and are placed close together, face-to-face, so that together they form a squared figure-of-8 shape. Each of the packs of plates has a notch which extends from the back of the E into its central arm and almost up to the end of the free end thereof. Conveniently, inserts of non-magnetic material are disposed in the notches in the packs of plates.