NOTE: Please ensure you have one of these daughter boards inside your ECU before continuing. If you have a standard black microprocessor, then you have an MS1 and these manuals are NOT for MS1 see here for MS1-Extra Manuals

Main Index of MS2-Extra Manuals

Layout of Components -- Suggested Supply points -- List of common components and part numbers

Dual trigger wheel (1 cam and 1 crank sensor or 2 cam sensors, etc)

Wiring Diagrams -- MegaTune Settings

Available in MS2/Extra 1.0 and 2.x codes.

This gives single coil, wasted spark or coil on plug (COP) spark outputs up to 12cyl wasted and 6cyl COP. (1.0 code only supported 8cyl WS/ 4cyl COP)

Triggering comes from a main trigger and a second typically cam trigger. Typical installs could be:
- a non-missing wheel on the crank and a single tooth on the cam (for coil on plug)
- a non-missing wheel on the crank and a two opposing teeth on the cam (for wasted spark or single coil)
- a missing tooth wheel on the crank and a single tooth on the cam (for coil on plug)
- double trigger setup driven at cam speed such as the 24/2 Nippondenso CAS etc.

For some instances of Nippondenso electrical systems, (Mazda and Toyota) this mode allows the use of the OEM CAS wheel and sensors without having to mechanically modify anything. These CAS have a 24 tooth wheel which rotates at half crankshaft speed. Either a single second pickup and wheel with 2 teeth, or two pick-ups with a single tooth can be used as a second input into MS-Extra.

Note: When using sequential COPs the second trigger input signals the first 360 degrees of a cycle. Therefore, the firing order of 1-3-4-2 would be sequenced Spark C-D-A-B if the second trigger happens on the second rotation of the crank or Spark A-B-C-D if it happens on the first rotation. If it shows sparking on cylinder #1 at the appropriate time and it does not start, try swapping 1&4 and 3&2 or reposition your second (cam) trigger by rotating it 180 degrees if possible

To use this feature you need to have an appropriate input signal conditioner for the main and second input. The second input is made to replicate the main trigger input but this is connected directly to JS10 (pin5 of JS1 on a V2.2) A daughter-board will be required to mount these components with a flying wire soldered directly to JS10. See HERE for more details.

The Trigger Angle/Offset is ignored in Toothed wheel mode, so leave it at zero. The angle used now is the angle that the next tooth (on the main wheel) is seen by the sensor after the 2nd trigger has pulsed. This is entered into Trigger Wheel Settings - Tooth #1 Angle.

If you are unsure what the angle will be then simply mark the tooth on the main wheel that is seen after the 2nd trigger pulses. Work out the angle between each tooth and find which tooth lines up at TDC. Then count back to the marked tooth and multiply that value with the angle between each tooth.

e.g.
       36 toothed wheel setup is 10deg between teeth (360deg / 36 teeth = 10deg)
       Mark the tooth that's seen just after the 2nd trigger tooth comes in.
       Turn the engine to TDC and count teeth backwards from the sensor to the marked tooth.
       Assuming its 8 teeth then 8 x 10deg = 80deg (Tooth #1 Angle)

       60 toothed wheel setup is 6deg between teeth (360deg / 60 teeth = 6 deg)
      Assuming its 19 teeth away then 19 x 6deg = 114deg (Tooth #1 Angle)

Wheel Speed - Refers to the main trigger input source (e.g. 60 toothed crank wheel or 12 toothed cam wheel, etc).

Every rotation of.. this is how often the active edge (or edges) happen. On a typical cam sensor with one tooth, this will be "Cam". If there were two teeth opposite each other then it would be "Crank". LS1 type triggers using the "Rising and falling" mode should be set to "Crank".

Second Trigger active on depends on the sensor used and wiring. If a VR sensor is in use, then use the active edge that the VR circuit gives you. There is only one right way. If a hall sensor is in use the one edge will be the start of the tooth/vane and the other the end of the tooth/vane and the phasing becomes important.

How critical this is depends on whether you are using a missing or non-missing main wheel.

With a missing-tooth main wheel, the missing tooth provides the main position reference to the Megasquirt. The cam signal should occur away (not co-incident with) the missing tooth, the exact angle is irrelevant, so long as they NEVER overlap.

With a non-missing-tooth main wheel, the second trigger / cam pulse provides the main position reference to the Megasquirt. Getting the position set correctly is now critical as the cam pulse must fall between the same two primary teeth under all conditions, it must NEVER overlap a tooth.

The first pair of signals show an active edge on the cam falling in between the two active edges of the crank. The Megasquirt only pays attention to the active edges you choose - shown here in green.

The next pair shows what not to do. Here the active edge of the cam is very close to the active edge of the crank and in the final pair of signals the cam has overlapped and the engine lost sync. If it regained sync like this (which it will do on the next revolution) the timing will be wrong by one tooth - which could cause grossly advanced timing and engine damage.

Note, refer to the hardware pages for spark driver instructions.

Suggested points for Supplies inside the V3.0 ECU

Component Pinouts

Pull up circuit diagram

List of component part numbers used in the ignition section:

Please note: Above part numbers will need checking, some components will come with a minimum order in multiples of 5 and 10.

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.