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Updated 1/17/2014
Types of MSD distributors
MSD offers several types of distributors. Here, we’ll focus on the familiar billet distributors, the kind with two wires coming out. MSD calls this a magnetic pick-up, but it is commonly referred to as a VR or variable reluctor sensor. Some MSD distributors have built in modules or behave like various factory distributors; these include the Ready To Run series, the Optispark replacement, E-Curve, and HEI distributors; this article does not cover MSD distributors with anything more than the basic two wire pick up. MSD Flying Magnet crank triggers also work in the same way as their magnetic pickup distributors as far as the MegaSquirt is concerned.
Note that if you’re running fuel only with the Megasquirt and the distributor is controlling the timing, just run the MSD tach output wire to the Megasquirt pin 24 and use the Hall / optical input circuit. This article assumes you are controlling the timing.
If you’re using a distributor with an advance mechanism, the first step is to lock out the advance. MSD generally makes this pretty straightforward and provides instructions for each specific distributor. There’s generally a bolt you can put in place to bolt the advance solid. We’ll assume you are using an MSD 6 series ignition with this, or similar, and have the box wired according to the MSD directions.
Once the distributor is locked out, you will want to adjust the distributor so the tip of the trigger wheel is pointed at the pick-up 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 some variations of the MSD box do not work well with BIP373s. We’ve seen this primarily crop up with a few Digital 6 variants. They only trigger if their signal is pulled down to nearly zero volts, and BIP373s do not pull the signal down quite as far as some other ignition outputs. If this occurs, you can substitute a different switching transistor such as a TIP120.
MSD ignition wire colors
“Positive” and “negative” can get confusing with VR sensors. This is how we use the term in this article. Hooking up the sensor backwards will cause the timing to retard; verify you are getting normal timing across the rev range before you start tuning.
| Distributor | Positive | Negative |
| MSD distributor | Orange and black | Violet and black |
| MSD Flying Magnet crank trigger | Violet | Green |
Using the MegaSquirt-I (MS1/Extra)
This is a straightforward option with a V3.0 or V3.57 board.
MegaSquirt-I PCBv3.0 Mods Required:
- Build the VR conditioner circuit, as described in the MS1 manual on MSExtra.com. All our preassembled Megasquirts with the V3.0 board come with this circuit installed.
- Jumper TachSelect to VRIN.
- Jumper TSEL to VROUT.
- You may need to adjust the VR trim pots, R52 and R56, when this is installed on a running engine. A usual base setting is to turn them all the way counterclockwise.
- Jumper IGBTOUT to IGN to send to IGBT ignition coil driver signal out of pin 36 on the DB37.
- Cut out R57 if fitted (This won’t be there on my units, though.).
- Get a 330 ohm 1/4w resistor and cut the leads down to about 1/2″ at each end. Maybe a bit less.
- Tin each end of the resistor with a bit of solder.
- Cut a 5″ piece of hookup wire (22ga is fine) and strip just a 1/8″ or so. Tin the stripped wire with solder.
- Melt the tinned wire tip to one end of the tinned 330 ohm resistor tip and let it cool.
- Heatshrink wrap this wire/resistor assembly.
- Use this wire/resistor combo to jumper the ‘top’ (top as in when you facing the silkscreen side of the PCB, with the text so that you can read it normally) lead of R26 to IGBTIN on the opposite side of the PCB.
That’s it!
MegaSquirt-I PCBv3.57 Mods Required:
- Set it up for VR input: Put the J1 jumper in the 1-2 position, and the JP1 jumper in the 3-4 position.
- You may need to adjust the VR trim pots, R52 and R56, when this is installed on a running engine. A usual base setting is to turn them all the way counterclockwise, then give both a half turn clockwise.
- Install a BIP373 coil driver in the Q16 slot.
- Get a 330 ohm 1/4w resistor and cut the leads down to about 1/2″ at each end. Maybe a bit less.
- Tin each end of the resistor with a bit of solder.
- Cut a 5″ piece of hookup wire (22ga is fine) and strip just a 1/8″ or so. Tin the stripped wire with solder.
- Melt the tinned wire tip to one end of the tinned 330 ohm resistor tip and let it cool.
- Heatshrink wrap this wire/resistor assembly.
- Use this wire/resistor combo to jumper pin 7 of the U1 socket (note: This socket is “upside down”, so pin 1 is in the lower right hand corner) to IGBTIN on the opposite side of the PCB.
That’s it!
External Ignition Wiring
- Connect the positive wire from the VR sensor on the distributor to pin 24 (Tach on the relay board). See notes at the bottom of this article for the wiring colors on various distributors.
- Connect the negative wire from the VR sensor on the distributor to a ground pin, such as pin 2 (or simply the engine ground on the relay board).
- Connect the MSD white wire to pin 36 on the Megasquirt (S5 on the relay board).
MSnS-E Ignition Configuration
- Under Codebase and Output Fuctions, set spark mode to MSnS and enable spark output using LED 17.
- You MUST set Spark Output Inverted to Yes.
- Set the dwell to fixed duty, 50%.
- The Trigger Angle setting will depend on the physical location of the trigger pickup. Often, an angle of 10 degrees will work. To set the timing with MSnS-E, go to the Spark Settings menu and set Fixed Angle to 10 degrees. You can then set the ignition timing to 10 degrees with the engine running, using a timing light. Once you have set the base timing, set Fixed Angle to -10. This will tell MSnS-E to use the timing map.
Using the MegaSquirt-I (MSnS-E) with a 7 Pin HEI module
If you happen to have a V2.2 board, using a HEI module can be easier than building a VR conditioner input circuit on a board that never had one (unless you use our Zeal Engineering Daughterboard). This is also a viable option on a V3.0 board, although it does use a bit more hardware (and one more output wire) than the direct coil control option. The MSExtra forums has detailed information about how to set up Megasquirt to work with an HEI ignition.
MegaSquirt-I PCBv2.2 Mods Required:
- The input mods are to invert the input signal from the HEI module’s tach signal. The HEI module will ground pin 24 to trigger a spark input.
- Remove D5, D8, and R10.
- Replace D8 with a 1.3 k resistor. You may substitute a resistor between 1.3 k and 2.0 k.
- Remove the jumper from XG1-XG2. Jumper XG1 to the right (non-banded) side of D5.
- Solder a jumper from the lower hole where R10 used to be (the hole nearest U4) to the upper lead of R11. This will provide a 5 volt pull-up.
- You will use LED 17 and LED 19 as outputs.
- Solder a 1 k resistor from the negative lead of D17 (it’s marked with a small – sign) to the right lead of R23 to provide a 5 volt pull-up on the output.
- Run a wire from the negative terminal of D17 to jumper X12.
- Now you will add the equivalent mod to D19.
- Solder a 1 k resistor from the negative lead of D19 to the right lead of R27.
- Run a wire from the negative terminal of D19 to jumper X11.
- That’s it!
MegaSquirt-I PCBv3.0 Mods Required:
- The input mods are to invert the input signal from the HEI module’s tach signal. The HEI module will ground pin 24 to trigger a spark input.
- Remove D1 and D2, if they are installed. Replace them with jumpers.
- Remove the jumper between XG1 and XG2 and any jumper leading to TachSelect, if fitted.
- Run a jumper wire from TachSelect to XG1.
- Run a jumper wire from OptoIn to one of the two +5V holes in the Proto Area.
- Remove C30.
- Replace R12 with a 1.3k resistor. You may substitute a resistor from between 1 to 2 k.
- Jumper OPTOOUT to TSEL.
- You will use two LEDs as ignition outputs.
- Connect a 1 k resistor from the +5V source in the proto area to the negative lead of D14. The negative LED leads are marked with small – signs on the board.
- Run a jumper wire from the negative lead of D14 to the IGN jumper hole.
- Connect a 1 k resistor from the +5V source in the proto area to the negative lead of D16.
- Run a jumper wire from the negative lead of D16 to the IAC1A jumper hole.
- That’s it!
External Ignition Wiring
- Connect a 12 volt switched power source to the + pin on the HEI module.
- Connect the MSD white wire to the C pin on the HEI module.
- Wire the distributor’s VR sensor to the HEI module, positive distributor wire to N and negative to P. See notes at the end of the article about which wire is which color.
- The R pin is the HEI module’s tach output. Connect it to pin 24 on the Megasquirt, or the Tach pin on the relay board. Note that the DIY Autotune wiring harness has a shielded wire – connect only the inner wire to this pin!
- Connect the E pin to pin 36 (relay board terminal S5) if you have a V3.0 board. If you are using a V2.2 board, use pin 27 or relay board terminal S2.
- Connect the B pin to pin 25 (relay board terminal S1) with either board.
MSnS-E Ignition Configuration
- Under Codebase and Output Functions, set HEI Ignition to “GM 7pin HEI” and the other options to Off.
- Set LED 17 function to Spark Output A, and LED 19 function to Spark Output B.
- In Spark Settings, set the Trigger Angle to 10 degrees and set Spark Output Inverted to No.
- To set the timing with MSnS-E, go to the Spark Settings menu and set Fixed Angle to 10 degrees. You can then set the ignition timing to 10 degrees with the engine running, using a timing light. Once you have set the base timing, set Fixed Angle to -10. This will tell MSnS-E to use the timing map.
- Under dwell settings, set dwell control to fixed duty and the spark output duty cycle to 50%.
Using the MegaSquirt-II PCBv3 or V3.57
These will also work for an MS3 without the MS3X.
If you’re assembling your MegaSquirt-II from a kit (Part# MS230-K):
- For the most part, stick with the standard assembly documentation and well cover any departures from that doc here.
- Step 51: 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).
- Step 52: Set the jumpers for VR input. That would be TachSelect to VRIN, and TSEL to VROUT.
- Step 65: 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).
- That’s it!
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)
That’s it– you’ve got your Megasquirt-II Engine Management System fully prepared to wire up to the Mopar distributor pickup, and drive the stock coil directly using the BIP373.
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)
That’s it– you’ve got your Megasquirt-II Engine Management System fully prepared to wire up to the Mopar distributor pickup, and drive the stock coil directly using the BIP373.
External Ignition Wiring:
- Connect the positive wire from the VR sensor on the distributor to pin 24 (Tach on the relay board). See notes at the bottom of this article for the wiring colors on various distributors.
- Connect the negative wire from the VR sensor on the distributor to a ground pin, such as pin 2 (or simply the engine ground on the relay board).
- Connect the MSD white wire 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 ‘Falling Edge’
- Cranking Trigger to ‘Trigger Rise’
- Coil Charging Scheme to ‘Standard Coil Charging’
- Spark Output to ‘Going High (Inverted)’
The Dwell setting will have very little effect, though the MS2 Manual recommends setting both dwell and maximum spark duration to 25.5 to get a square wave signal with a 50% duty cycle. Setting dwell and maximum spark duration to 8.0 will work without changes to the INI files.
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 ‘Falling 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 ‘Fixed Duty’ and use 50% duty cycle
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.
Using the MegaSquirt-III PCBv3 or V3.57 and MS3X
Note that a standard MSD distributor does not support sequential injection as it has no provision for cylinder identification. An MS3 does not need any specific mods when using the MS3X. If building it from a kit, just set it up for VR input. Our assembled units are jumpered for VR input out of the box. You may need to adjust the VR trim pots, but that’s about it.
External Ignition Wiring:
- Connect the positive wire from the VR sensor on the distributor to pin 24 (Tach on the relay board). See notes at the bottom of this article for the wiring colors on various distributors.
- Connect the negative wire from the VR sensor on the distributor to a ground pin, such as pin 2 (or simply the engine ground on the relay board).
- Connect the MSD white wire to MS3X pin 26 (tach output).
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 ‘Falling Edge’
- Spark Output to ‘Going High’
- Number of coils to ‘Single coil’
- Spark A output pin to ‘Tacho’
- Dwell type to ‘Fixed Duty’ and use 50% duty cycle
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 direct from the manual:
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.)
