Bosch HEC 715 Ignition Coil

Bosch HEC 715 Ignition Coil

Haltech Part Number HT-020110


The HEC (High Energy Coil) series of ignition coils are manufactured by Bosch and have a number of various models.  The 3-digit code simply changes the orientation of the wiring connectors and the connector type, and also the type of spark discharge post.  Otherwise all models have the same coil specifications.  Bosch state that the coil is designed for Generic Use or Custom Applications.  

The HEC726 with male "spark plug" style discharge post

Old Design

Bosch redesigned the coil a number of years ago with the previous type having a different look.

Old style HEC715



The configuration is for the Haltech HPI igniter.
Haltech Elite Series Setting
Ignition Mode
Installation Dependent
Ignition Edge
Ignition Dwell Mode
Constant Charge


The HEC deisgnt is thermally limited in high long the coil can be charged.   Full coil saturation does not occur until a high dwell time, however maintaining the coil at full capacity can cause it to become hot.  As such the dwell time needs to be left lower than normal to maintain reliability, and only under high power demands should be dwell to configured to give full spark energy.  To achieve this the dwell table can be mapped over battery voltage and also engine load.  

Below is an example of how this can be achieved.

At a normal running 14V the coil is charged at a lower time under conditions off boost.  As boost pressure rises the dwell will gradually increase until it peaks around 200kPa (~30psi) where full spark energy is then available.  This allows excellent spark energy together with good reliability. Also at lower voltages such as when the engine is cranking the dwell time is also lifted to ensure a strong spark to aid engine starting.

Wiring and Igniter Module

The HEC coil does not have an internal igniter so and external igniter is required.  They can draw around almost 20A of current at peak charge so a high current igniter such as the Haltech HPI units are highly recommended.

Haltech HPI8


12V Power Supply

The HEC coil can draw near to 20A.  If high rpm and high power is being used, together with conventional 30A Relays to provide power, it may be necessary to have a separate fuse and relay for every pair of coils.  This has been seen on some rotary installations where over 10,000 rpm is used together with high boost.

If the wiring is also not cable of supplying the current required it can also limit the spark output.

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