How to Use MegasQuirt With the PerTronix Ignitor

Taking control of the timing with a Pertronic Ignitor

The PerTronix Ignitor is a small, self contained ignition module that replaces breaker points. PerTronix also offers ready to run distributors that come equipped with the Ignitor. If you are using the distributor advance mechanism to control the timing, you can simply follow the directions for fuel only and triggering off the negative terminal of the coil. This article covers the other possibility: locking out the distributor and having the MegaSquirt control timing. When you do this, the PerTronix functions as a sensor for the MegaSquirt, with the MegaSquirt firing the coil. Although the Ignitor uses a Hall effect sensor, it is not possible to wire MegaSquirt to this sensor directly. You’ll need to use the ignition control output instead.

First, you will need to lock out the distributor. With PerTronix’s own distributor line, they have a simple lock-out kit; use part number D703700 for counter-clockwise rotating distributors and part number D9010 for clockwise rotating distributors. For OEM points distributors, how to lock it out will depend on the distributor and may require welding parts together.

Once the distributor is locked out, you will want to adjust the distributor so the Ignitor would fire the coil somewhere between 1 and 19 degrees BTDC, and have the distributor rotor aligned so the center of its tip points at the #1 distributor cap tower at around 20 to 30 degrees BTDC. This is called distributor phasing, and is important to be sure the spark can travel to the spark plugs when the coil fires.

Note that MegaSquirt will not work with the Ignitor III, either in fuel only or using it as a trigger for MegaSquirt controlled ignition. The problem is that the Ignitor III sends multiple spark signals per ignition event, and does not have a tach output with a single pulse per ignition event. This prevents it from providing a usable signal to trigger the MegaSquirt or other electronics. As PerTronix’s Ignitor III documentation notes, “We recommend the Ignitor or Ignitor II as a trigger source for a capacitive discharge box“, (bolt printing in the original) and the same warning applies to using the Ignitor III as a trigger for MegaSquirt or other EFI controllers.

Using the MegaSquirt-II PCBv3 or V3.57

Note: MS3 can handle this in a similar way. Note that this approach does not allow you to use sequential injection; this would require adding a crank trigger and removing all but one magnet from the PerTronix trigger.

If you’re assembling your MegaSquirt-II from a kit (Part# MS230-K):

  • For the most part, stick with the standard assembly documentation in the MSExtra MS2 Manual.  I’ll just be covering any departures from that doc here.
  • Additional:  You’ll be installing the VR input circuit  (currently all steps under 51). You do not need the components in step 50, although it’s handy to install them in case you ever use the Megasquirt on a different car (or decide to convert your Mopar to a ignition system that uses this circuit).
  • Additional 2:  Set the jumpers for VR input.  That would be TachSelect to VRIN, and TSEL to VROUT.
  • Additional 3:  You will use IGBT High Current Ignition Driver Circuit.  That means you complete step 65.  Install everything just as this step directs you to (which does mean no R57) and install the jumpers to enable the circuit. (IGBTIN to JS10 and IGBTOUT to IGN).

If you’re modifying a DIYAutoTune.com MS230-C MegaSquirt-II Assembled ECU:

Input Mod:

  • You will be using the VR input circuit. Connect the TachSelect jumper to VRIN, and TSEL to VROUT

Output Mod:

  • There will be a jumper wire from JS10 over to IGN.  Desolder and remove this (don’t just cut it, you’ll need the holes clear of solder).
  • Install new jumper wires to enable the IGBT High Current Ignition Driver Circuit (IGBTIN to JS10 and IGBTOUT to IGN)

If you’re modifying a DIYAutoTune.com MS2357-C MegaSquirt-II Assembled ECU:

Input Mod:

  • You will be using the VR input circuit. Place the JP1 jumper in the 1-2 position, and J1 in the 3-4 position

Output Mod:

  • There will be a jumper wire from JS10 over to the center hole of Q16.  Desolder and remove this from the center hole of Q16 (don’t just cut it, you’ll need the holes clear of solder).
  • Install a BIP373 coil driver transistor in the Q16 slot.
  • Install new jumper wires to enable the IGBT High Current Ignition Driver Circuit (IGBTIN to JS10)

External Ignition Wiring

  • Connect the black wire on the Ignitor to pin 24 (Tach on the relay board).
  • Connect the red wire on the Ignitor to a switched 12 volt source.
  • Use a 1K resistor to connect the red and black wires of the Ignitor together.
  • Connect the negative terminal of the coil to pin 36 on the Megasquirt (S5 on the relay board).

TunerStudio Ignition Configuration for Bowling & Grippo firmware:

  • Trigger offset = 10 (this will vary, depending on the distributor orientation, see notes at the end of the article)
  • Ignition Input Capture to ‘Rising Edge’
  • Cranking Trigger to ‘Trigger Rise’
  • Coil Charging Scheme to ‘Standard Coil Charging’
  • Spark Output to ‘Going High (Inverted)’

TunerStudio Ignition Configuration for MS2/Extra or MS3:

  • Spark mode to ‘Basic Trigger’
  • Trigger angle / offset = 10 (this will vary, depending on the distributor orientation, see notes at the end of the article)
  • Ignition Input Capture to ‘Rising Edge’
  • Spark Output to ‘Going High’
  • Number of coils to ‘Single coil’
  • Spark A output pin to ‘JS10’ if using our build guide above
  • Dwell type to ‘Standard Dwell’

Dwell will need to be set depending on the coil. 2.5 to 3.5 msec is usually a good starting point.

More information on setting Trigger Offset:

You must also set the initial position of the trigger (called the ‘trigger offset’), then check it using the Trigger Wizard in TunerStudio  (Tools Menu).  The trigger offset setting will vary according to your distributor position (where it is in rotation) but you’ll need to set it properly…  Basically you use the Trigger Wizard and adjust the ‘trigger offset’ and/or twist your distributor until the advance number in the Trigger Wizard matches what you’re reading with your timing light.  The +/- buttons on the trigger wizard will adjust your trigger offset.  You’ll need to use these buttons and a timing light to make the number on your light, and the big number on the left in the Trigger Wizard, match up.

Here’s the information on this:

Before tuning your advance table, be sure to use a timing light to verify that your ‘trigger offset‘ is calibrated. Changing the Trigger Offset in MegaTune will not change the displayed advance, instead, it changes the actual advance as seen with a timing light. Your goal is to make these two match.

To do this, get your engine warmed-up (otherwise the timing moves as the temperature increases) and idling, then use a timing light to verify to be certain your actual advance as shown by a timing light equals your the advance display on the advance gauge in MegaTune. (8 in this case). (Note that positive numbers denote BTDC, and negative numbers denote after TDC.)