Megasquirt (V3.0 board) - Spark/ignition output

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Logic-level ignition output -- High current ignition output -- Output to CDI box

Introduction
Before commencing wiring, be sure to have identified the ignition coils you are using and determined if they are high-current or logic-level type; or whether you are using a CDI box.

All ignition outputs require a certain level of customisation inside the Megasquirt box.


Logic level ignition output
When using logic level coils or an external ignition module, the ECU needs to be configured to supply logic-level outputs.
The diagram here shows the connections required for four channels (e.g. 4cyl COP or 8cyl wasted spark.) If 5th and 6th logic channels are required, build additional transistor circuits with the inputs JS5 and JS4 and route the output from the circuits to spare output pins of your choice.

The Spark Output Polarity is almost always "Going Low" in this configuration.

MS3 users can use the MS3X output card which gives 8 channels of logic spark without the need for any customisation. See here.

5V PNP drive for VAG logic COPs

V3.0 PCB 5V PNP drive diagram:

For a 4cyl sequential setup you would need to have 4 of these circuits rather than the 2 below, simply repeat the additions for Spark C and D so
Spark C point to connect the 1K resistor is:
V3.0 PCB - Top of R27
Use SPR2 for the 2N4033 collector's connection - Spark C will be on pin 4 of db37

Spark D point to connect the 1K resistor is
V3.0 PCB - JS11 pad
Use SPR3 for the 2N4033 collector's connection - Spark D will be on pin 5 of db37


Similar parts instead of the 2N4033 are: 2N3906, PN2907, PN3645, BC327, MPS2907, 2N4403, ZTX5533

Try Spark Out - Going Low (Normal) to start with,
ensure you keep an eye on the temp of the COP when you first turn ignition ON!!
If it gets hot try SPARK INVERTED = YES


High current ignition output using internal drivers
For Megasquirt-1 and Megasquirt-2 it is common to customise the ECU to install high-current ignition drivers (BIP373) internally. This allows the ECU to directly drive high current coils or coilpacks. One driver is required per coil channel.
Optionally you could configure the board for logic spark output and use external ignition modules, this would have the advantage of keeping high currents and electrical noise outside the main ECU.

Single Coil Output (Distributor) -- MSD Amplifier -- 2 Coil Outputs (4cyl Wasted Spark)

3 or 4 Coil Outputs (6 and 8 cyl Wasted Spark or 4cyl COP)

Driving 2 Coils from the same Spark Output (6 or 8 cyl COP)

 

 


Single Coil Output (Distributor Based)

To control the coil (single coil driven through the distributor to the correct cylinder) you will need to build the BIP373 circuit to your MS ECU.

Very Important: Set Spark Out - Going High (Inverted) and set the Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.
See HERE for settings

 

Very Important: Set Spark Out - Going High (Inverted) and set the Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.
See HERE for settings

 

Settings for 1 coil (Distributor Based)

       


Two Coil Outputs (4cyl Wasted Spark)

When running 2 coils directly from the ECU it is highly recommended you fit an extra copper cable (a piece of wire snipped from the leg of a diode or the like is fine) from the Spare terminal you are going to use (e.g. SRP4) to its terminal directly on the 37pin connector, (e.g. SPR4 to Pin 6), this is because the copper trace for the SPR connectors are designed for small signals voltages and not coil driver currents. This means you'll have to lift the MAP sensor up (unbolt it first :o) ). Also ensure the main earth lead is thick enough to cope, I use a 4mm cable connected to pins 8 and 9 of the DB37 connector (this is probably an over kill, but 0.75mm wire isn't good enough).

Start by wiring in the first BIP373 as the single instructions (HERE)

The second BIP373 can then be wired like this: (Please Note: I have assumed that R37 and R38 are not installed on this diagram, these need to be removed and linked out with a piece of copper wire. Alternatively keep R37 and R38 in place and bolt the new BIP373 onto the lid of the MS ECU)
Leaving R37 and R38 in place is preferred.

As a side note I generally mount the TIP122 Idle control FET in position R37 and the second BIP373 as shown in position R38:

 

Very Important: Set Spark Out - Going High (Inverted) and set the Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.
See HERE for settings

Settings for 2 coils (4 cyl wasted spark)

       

Ignore the Spark mode in this example, that will depend on your setup, main points here are:
Set
Spark Out - Going High (Inverted) and set the Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.


Three or Four Coil Outputs (6 and 8 cyl Wasted Spark or 4cyl COP without ignitors)

When running more than 2 spark coil outputs directly from the MS ECU it is recommended that you fit a new connector (e.g. DB15) to the case (as we recommend for all V2.2 spark outs). The reason is that the ground cable / copper trace is not designed to take the current of the additional coils and it may also cause interference on the MS's ground plain. So to be safe simply drill and file out a slot for a new DB15 connector where the LED holes are in the front panel. Then mount the BIP373's onto the lid of the case or underneath the MS board on another alluminium heat bus bar bolted through both sides. If mounting them on the lid, fit them so when the lid is in place the FET's end up on the bottom left corner, so when the lid is inverted like the picture they are at the top, this will ensure there is plenty of clearance for them inside the ECU when the lid is in place.

The COP setup is for modules without a built in ignitor (2 or 3 wired devices) for 4 or 5 wired COPs see HERE

Note: This db15 is NOT the same as the V3.57 PCB db15, that can be used but you would need to strengthen the copper traces on the PCB and you would need to select different pins to the ones shown is these instructions!!!!

Using the following diagram would mean removing the LED's from the pcb, simply remove them and do nothing else to the holes they leave.

3 x BIP373's mounted on the lid. DB15 connector on front panel

Remember you only need to fit the same amount of BIP373's as you require outputs. e.g. 2 x BIP373's (Spark A + B) for a wasted spark 4cy, 4 x BIP373's (Spark A + B + C + D) for a wasted spark 8cy, etc.

For COP coils that have no built in ignitor (2 or 3 pinned devices):

 

 

Settings for 3 or 4 coils (6 and 8 cyl wasted spark)

Wasted Spark Setup (e.g. 6 or 8cy)

Ignore the Spark mode in this example, that will depend on your setup, main points here are:
Set
Spark Out - Going High (Inverted) and set the Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.

Settings for sequential COP

To run sequential COP you MUST have a suitable cam signal:
* Missing tooth wheel at cam speed
* Missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at crank speed + single tooth at cam speed
* Non-missing tooth wheel at cam speed + single tooth at cam speed
The cam signal could be as simple as a magnet on the timing pulley and a hall sensor in proximity to it.

Ignition Options Sequential COP

Trigger Wheel Settings Sequential COP

   

Ignore the Spark mode in this example, that will depend on your setup, main points here are:
Set
Spark Out - Going High (Inverted) if using the BIP373 circuit,
If using a COP with an ignitor try
Spark Out - Going Low
Set the
Dwell to around 6.0mS for cranking 3.5mS for Running and 0.1mS for the Minimum Time as a starting point! Also set D14 as the Spark A output pin.


Driving two coils from the same spark output e.g. 4cyl COP without ignitors (wasted spark format) 6cyl and 8cyl COP without ignitors

The MS2 can drive a maximum of 6 spark outputs. Therefore an 8 cylinder engine can be run as either wasted spark or wasted-COP setup with ignitors off the same spark output to directly drive the COP's.

The COP setup is for modules without a built in ignitor (2 or 3 wired devices) for 4 or 5 wired COPs see HERE

In order to drive 2 coils from the same spark output the wiring is very similar to the multiple wiring, except that there are now 2 x BIP373's per spark output.

Note: This db15 is NOT the same as the V3.57 PCB db15, that can be used but you would need to strengthen the copper traces on the PCB and you would need to select different pins to the ones shown is these instructions!!!!

Important note: One BIP373 can only drive a single coil, do NOT wire 2 coils to one BIP373.

Example shows a 4cyl setup:

Again it is recommended that you fit a db15 connector to the MS ECU in place of the LED's, if using a 6 or 8cyl engine then fit a 25pin db connector instead of a 15pin.

 


External CDI box
One option for ignition coil drive is to use an external CDI box to drive a single coil. MSD is a well known brand and we will cover their wiring scheme here. Other manufacturers use similar wiring colours, but check the supplied diagrams.

With an MSD box, the ignition module wires you need to know about are:

With the MSD ignition box, we use the white 'points' input wire. Do not connect anything to the green and violet wires. The MSD box is only being used to fire the coil. The Megasquirt must receive its tach input from a crank or distributor pickup.

When using the MSD digital 6 box in particular, some have experienced problems with the above layout as the ignition transistor Q16, does not give a true ground output. Try the following alternative instead.


 

 

 

Settings

    

Set the Spark Output to Going High (Inverted)
Number of coils
to Single Coil
Dwell
to Fixed Dwell of Dwell Duty 50%


If you have a question, comment, or suggestion for this FAQ please post it on the forum.

No part of this manual may be reproduced or changed without written permission from James Murray, Ken Culver and Philip Ringwood.