How do I perform a direct fire ignition conversion on a Mazda RX-7 FC?

If you are converting an FC RX-7 to a standalone direct fire ignition, it is almost always because you have switched to a carburetor (like a Mikuni or Weber) and removed the factory ECU, but want to avoid the cost of a standalone engine management system like a Megasquirt ¹.

In the rotary community, this conversion is commonly referred to as 2GCDFIS (2nd Gen Coil Direct Fire Ignition System) or DLIDFS (Distributorless Ignition Direct Fire System) ¹.

The FC actually comes from the factory with a direct-fire, waste-spark leading coil. The challenge is triggering that coil pack without the factory ECU. Based on general automotive practice for this platform, the standard workaround is to use a 1st-generation (FB) RX-7 electronic distributor to read the engine position and trigger the FC coils.

Difficulty: Moderate

Here is the standard procedure for setting up a 2GCDFIS on an FC:

1. Mechanical Setup

• Find Top Dead Center (TDC): Rotate the engine by hand until the front rotor is at TDC. Align the main pulley's yellow timing mark with the indicator pin on the front cover.
• Remove the CAS: Unbolt and pull out the FC's factory Crank Angle Sensor.
• Install the FB Distributor: Drop a 1981-1985 1st-gen RX-7 electronic distributor into the CAS hole. Make sure the dimple on the distributor gear aligns with the mark on the distributor housing before you drop it in so the rotor points to the leading ignition terminal when fully seated.

2. Wiring the Ignition (General Practice)

Because you no longer have an ECU to interpret the distributor's magnetic pickups, you need igniters to translate that signal for the coils. The most common and reliable method is using GM HEI 4-pin ignition modules.

• Leading Ignition (Waste Spark):
  • The FC leading coil fires both front and rear rotors simultaneously.
  • Wire the leading magnetic pickup from the 1st-gen distributor to a GM HEI 4-pin module.
  • Wire the output of the HEI module directly to the trigger wire on the FC leading coil pack.
  • Make sure the HEI module is mounted to an aluminum heatsink with thermal paste, or it will burn up quickly.
• Trailing Ignition:
  • The FC trailing coil setup is complex and relies heavily on the stock ECU to toggle the spark between the front and rear rotors.
  • To bypass this, standard practice is to ditch the FC trailing coil completely. Instead, run two standard 12-volt ignition coils (like FC leading coils or MSD Blaster coils) driven by two more GM HEI modules, triggered by the trailing pickup in the distributor.
  • Alternatively, some track-only builds just leave the trailing ignition disconnected entirely and run on the leading plugs alone, though you will sacrifice some power and emissions cleanliness.

3. Setting the Timing

I don't have a verified base timing figure for your specific car, as optimal ignition advance depends heavily on your exact carburetor jetting and whether your 13B has a stock, street, or bridge port. Do not guess this number—check with your engine builder or consult a factory service manual for the baseline specs.

The procedure to set it, however, is straightforward:

1. Connect a timing light to the front rotor's leading spark plug wire.
2. Start the engine and let it reach operating temperature.
3. Loosen the distributor hold-down nut.
4. Shine the timing light at the main pulley and rotate the distributor housing by hand until your target timing mark aligns with the indicator pin on the front cover.
5. Tighten the hold-down nut and re-verify the timing hasn't shifted.