Upgrading to Denso Ignition Coil-on-Plugs

A good upgrade to the stock ignition system for a Miata-based engine is to upgrade to a Coil-on-Plug ignition system. We chose to install the Denso Ignition Coil-on-Plugs which should give us a much better spark for when we turbo our Exocet.

We bought our used Coil-on-Plugs for just $50 on ebay which is significantly cheaper than anywhere else.

The stock coil pack was super heavy and bulky and removing it allows us to save weight and space.

In order to secure the new Coil-on-Plugs and prevent them from popping out, we fabricated a mounting bracket using a strip of aluminum and some bolts and nuts.

We sealed up the gap between the mounting bracket and the valve cover with some silicon gasket sealant to prevent moisture from seeping into the spark plugs.

With the Coil-on-Plugs in place we built our own custom wire harness.

Now with all the hardware is in place, we made a few changes to the ignition settings in our Megasquirt ECU to account for the Coil-on-Plugs and to switch to sequential ignition. The stock ECU uses a wasted spark system in which at least two spark plugs would fire at a time. With sequential ignition, only one spark fires at a time allowing the spark plugs and coils to have a much longer lifespan.

The main settings we changed were:

  • Number of Coils -> Coil on Plug
  • Cranking Dwell -> 3.5
  • Nominal Dwell -> 2.5

With this new ignition setup, the engine bay is much less cluttered and the engine runs noticeably smoother.

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