MS2-Extra Dual Wheel Manual

Only for use with the MS2-Extra code (HC9S12C64 based microprocessor - MS2 Daughter Board)

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

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Please Note:

All of these instructions / diagrams are to be used at your own risk, like most things there is more than one way to do the same thing, what we have tried to do is to offer a method that we have tested or that others have tested for us. No warranty expressed or implied.

Use at your own risk.
If you do have any suggestions or settings that work please let me know
Philip.Ringwood(at)ntlworld.com


Main Index of MS2-Extra Manuals

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

Wiring Diagrams -- Settings

This gives single coil, wasted spark or coil on plug (COP) spark outputs up to 12cyl wasted and 6cyl COP.

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

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 it is possible for the phase to be 360 degrees off. If it shows sparking on cylinder #1 at the appropriate time and it does not start, try adding 360 to your tooth#1 angle

To use this feature you need to have an appropriate input signal conditioner for the main and secondary tach inputs. These are already included on the Microsquirt, but MS2 installs will require customisation.

Sensors and wiring

For all ignition pickup / tach inputs, see the tach input page

For all coils and spark outputs, see the spark output page

Settings

The Trigger Angle/Offset is ignored in Toothed wheel mode, so leave it at zero. The critical settings is called 'Tooth#1 angle' See diagrams below for definition.

Ignition Options for Toothed Wheel - Dual Wheel

60-2 Main (Crank) wheel

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".

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.
It is not advised to use high tooth-count non-missing crank wheels as slop in the timing belt or chain will likely cause a loss of synchronisation.


Phasing diagrams

Missing tooth crank wheel and single tooth cam wheel

What is Tooth #1

Make sure you understand this!
With the engine rotating in the normal direction...

Tooth #1 is the first tooth to pass the sensor after the missing tooth gap.

To confirm correct cam sensor phasing proceed as follows.
First, set your engine at TDC compression #1
Now rotate the engine backwards to tooth#1
The angle read off the damper is the tooth#1 angle
Now rotate the engine backwards some more - this is the best place for the cam tooth to pass the sensor.

Non-missing cam wheel and second cam wheel

What is Tooth #1

Make sure you understand this!
With the engine rotating in the normal direction...

Tooth #1 is the first tooth to pass the main sensor after the single tooth has passed the second sensor

Make sure these do not happen at the same time - in the diagram you can see that the main sensor is over a gap when the secondary sensor is aligned with its tooth.
First, set your engine at TDC compression #1
Now rotate the engine backwards until the 'cam' sensor and tooth line up.
If you rotated more than one turn, then add 360 to your tooth#1 angle.
Now rotate the engine forwards until the next 'crank' tooth aligns with its sensor.
The crank angle now is the tooth#1 angle.
(Note that angles shown in diagram are examples only)




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.

Based on the original MegaSquirt® tuning guide: ©2008 Bowling and Grippo. Used with permission.