Main Index of MS2-Extra Manuals

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

Missing tooth crank or cam wheel

Mounting the Wheel and VR sensor -- MegaTune Settings -- Wiring Diagrams

Available in MS2/Extra 1.0 and 2.x codes.
This is a new implementation in MS2/Extra and gives single or wasted spark outputs up to 8cyl wasted.

The wheel decoder allows the use of a multi-toothed trigger wheel such as 36-1 (commonly fitted to Fords), 60-2 (used mainly by Bosch and therefore very widespread in Europe.)
See www.trigger-wheels.com for a supplier of custom made wheels. Other custom wheels such as 6-1 or 4-1 also work.
The code supports:

Fuel only

Single coil (distributor based setup)

Wasted spark with multiple coils

Coil on Plug (run in a wasted spark format)

For wasted spark you require a minimum of single "missing tooth" crank wheel, only engines with an even number of cylinders being supported. You need at least 4-1 for 4cyl, 6-1 for 6cyl or 8-1 for 8cyl. However, the 36-1 wheel is probably the easiest to obtain. The MS2 ECU can drive up to 4 seperate spark outputs, meaning it can run up to an 8 cylinder in wasted spark mode. (4cy, 6cy and an 8cy)

For Dual Wheels (Cam sensor as well as Crank sensor or 2 Cam sensors, etc) and for real Coil on Plug see Dual Trigger Wheel

The easiest install will be wasted spark using VB921 FET's to drive the spark coil(s) directly from a V3.0 PCB. (See the Spark Output selections available HERE) In this way it can be used like EDIS but without the need for an EDIS module, it has the advantage of allowing spark cut rev limiting. The downside is that it is more difficult than EDIS and requires extra software settings. If you are buying a pre-assembled Megasquirt (e.g. www.ExtraEFI.co.uk) your vendor will be able to do this for you.

Where to mount the sensor and wheel

Lets asume your going to change a distributor based setup over to a wasted spark coil pack setup. The changes needed will be different for each engine but the basics should be the same: A wheel will need to be fitted on the crank pulley, a VR (Variable Reluctor) sensor will need to be mounted to detect the wheel and a set of coil packs will need to be mounted onto the car.

Typical trigger discs (36-1) from a Ford VR Sensor

Mounting the wheel is quite critical in that it MUST be mounted so it rotates without moving up, down, left or right as the sensor needs to see all of the teeth with a gap of 0.75 - 1.0mm. The VR sensor can be found on vertually all Fords that have a coil pack under the bonnet, you'll need the coil pack too, so get them both at the same time, also keep the HT leads as the connectors will be needed. The VR sensor is usually mounted on the bell housing somewhere, depending on the engine.

When fitting the wheel set the engine to Top Dead Centre (TDC) if you fit the sensor so it aligns with tooth 9, as the following diagram, then you can use a "Tooth #1 Angle" of 80deg. This will be the same for all engines regardless of the amount of cylinders.

A 4 - 1 Tooth setup:

The Trigger Angle/Offset should not be used in Toothed Wheel mode, so leave it at zero. The angle used now is the angle that Tooth #1 passes the sensor at, this is set in Trigger Wheel Setting

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.

We use the term "tooth#1" as it is consistent across wheels with one, two, three or four missing teeth in the group.
Once the code knows the tooth#1 angle it automatically calculates other needed information internally. (No need to manually enter trigger teeth or delay teeth etc.)

Clockwise rotation (normal) - method a Set your engine at TDC, then count the number of GAPS to tooth#1 in the direction of rotation (clockwise here) and multiply by the angular size of the tooth. e.g. 8 teeth * 10 deg per tooth = 80 deg 36-1 wheels are 10 deg per tooth (360 deg / 36 teeth) 60-2 wheels are 6 deg per tooth (360 deg / 60 teeth) 24-2 wheels are 15 deg per tooth (360 deg / 24 teeth)
Clockwise rotation (normal) - method b A different way of looking at the SAME phasing. Turn your engine so that tooth #1 aligns with the sensor. Read off the tooth#1 angle from timing marks/tape on the crank pulley.

e.g. Typical Ford Setup:
       36 -1 setup is 10deg between teeth (360deg / 36 teeth = 10deg)
       Tooth 9 lines up with sensor at TDC, so tooth 9 to tooth 1 = 8 teeth
       Therefore 8 teeth x 10deg = 80deg (Tooth #1 Angle)

      Typical Vauxhall/Peugeot (and other Bosch) setup
       60-2 setup is 6deg between teeth (360deg / 60 teeth = 6 deg)
      Tooth number 20 lines up with sensor at TDC, so tooth 20 to 1 = 19 teeth
      Therefore 19 teeth x 6deg = 114deg (Tooth #1 Angle)

Ignition Options for Toothed Wheel	36-1 wheel setup in Trigger Wheel Settings

For most installs set the Ignition Capture to Rising Edge. See the Ignition Input options HERE.

If using VB921's to directly fire the coils set the Spark Output to Going High (Inverted)

The Number of Coils is simply dependent on your coil setup. If you have coil packs, 1 coil firing 2 cylinders, (so 2 coils on a 4cy or 4 coils on a V8) then select Wasted Spark. If you have a distributor then select Single Coil, if you have Coil on Plugs (4cy engines ONLY) select Coil on Plug. Dual Dizzy is for setups with 2 distributors (e.g. Lexus)

Internal Wiring

Spark outputs come on D14 and D16, see HERE for options on driving the coils.

V3.0 PCB:

V2.2 PCB:

The circuit below will need to be made for a V2.2 board

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.