Megasquirt (V3.57 board) - Spark/ignition output

This page has now been superceded, please click here

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. The V357 board makes it easy to access 3 logic ignition channels, but as the board was not designed for DIY modifications, any other changes can be more awkward than the DIY V3.0 board.

Note that all diagrams showing a 15 pin DB connector are for an ADDITIONAL CONNECTOR. The built in DB15 on the V357 board can be used, but you need to choose suitable pins and ensure the connections are thick enough to handle any ignition current.

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 simple jumper connections required for the first three channels. 4th, 5th, 6th channels require additional transistor circuits to be built.

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
Not shown. See the V3.0 page for a similar design.

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.

When using internal high current coil drivers, the Spark Output Polarity is almost always "Going High".

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

Settings for 1 coil (Distributor Based)

Two Coil Outputs (4cyl Wasted Spark)

When running 2 spark coil outputs directly from the ECU you will need to install an addition ignition driver (BIP373) using the same circuit diagram as shown above. It is important that this is installed on a heatsink or screwed to the case. The ignition driver can either be bolted to the case lid or on an additional heatsink bar mounted on top of the first. Remember to use the insulator kit so that there is no connection between the metal tab and the heatsink. Use the RHS of R37 or R38 as a power ground connection.

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

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 ECU you will need to install addition ignition drivers (BIP373) using the same circuit diagram as shown above. Be sure to use plenty of power ground connections on the main connector to the engine block.

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.

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)

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.

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

Example shows a 4cyl setup:

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:

tach signal is a yellowwire (do not use this to feed to pin #24 on MegaSquirt, it is for a tachometer only)
advance control signalis a white wire
ground is a heavy black wire
power is a heavy red wire
switched 12 volts is a thin red wire
the coil positive (+) wire is orange
the coil negative (-) wire is thin black
the unused VR signal wires are green and violet.

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.