Mitsubishi 4G63 DSM CAS MS2/Extra 3.57 PCB Yoshifab Disk

[jsdevel]

This post is a sanity check, so if other members could confirm the synopsis at the end of the post I'd appreciate it.

Hello all,

I'm still a newbie to megasquirt. Currently preparing my MS2/Extra 3.4.x / 3.57 PCB board to handle this DSM CAS using Yoshifab's 24/1 trigger disk:



I've been reading the manual and other forum posts for several months now and believe that I've finally stitched together the relevant instructions that are spread throughout the manual.

Relevant sections from the manual (Dated 2016-02-02):

5.2 Crank and Cam tach inputs

Installs requiring a second tach input (cam sensor or part of a CAS) will require additional internal modifications.
See section 5.2.14

5.2.3 Hall sensor input

There are two main categories of hall sensor

• open-collector (needs a pull-up resistor)
• built-in pull-up resistor (covered in section 5.2.4)

The hall sensor requires a supply voltage which is usually 12V from a fused 12V supply or 5V from the TPSREF output of the Megasquirt. The sensor is then grounded at the Megasquirt sensor ground and the signal wire connects to the Tach input. A pull-up resistor is required in the wiring harness or inside the Megasquirt.

VR Input with pullup for hall sensors, LS2/58X, optical sensors or points

1. Find JP1 in the bottom right of the board. Place a jumper across positions 1 and 2
2. Find J1 in the middle of the board. Place a jumper across positions 3 and 4
3. Install a 1k resistor (any value 470R - 2k2 is likely ok) onto the pads marked R57
4. With a small screwdriver, turn the pots, R52 and R56, 7 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.) and then turn R56 back about 2 turns clockwise.

Optionally, when adjusting R56, you can measure the voltage at the "top" of R54. You'll need the board powered up. Set your meter to volts, and connect the +ve probe to the top of R54 and the -ve probe to ground. Adjust
R56 to get around 2.5V on your meter.

5.2.13 Mitsubishi CAS with aftermarket disc

When this kind of replacement trigger disc is installed the "Toothed Wheel" mode needs to be used - see section 6.9

5.2.14.2 Adding a cam sensor input - hall sensor / optical sensor

This option uses the spare opto-isolator on the mainboard for the cam input and matches the polarity inversion of the VR/universal tach input. This section is for open-collector sensors as covered in 5.2.3 that ground switch only.

1. JP1/pin3 should be connected with a jumper wire to a spare pin on the main DB37 connector (e.g. SPR3)
2. Connect J1/pin1 with a jumper wire to JS10 (ensuring that nothing else is connected.)
3. Jumper XG1 - XG2
4. Check that R12 is a 390R to 470R resistor, replace if not.
5. Solder wires onto a 470R 1/4W resistor and cover in heat-shrink.
6. Connect one wire to +5V
7. Connect the other wire to JP1/pin3 (joining the jumper wire there.)
8. Ensure that C30 is not fitted.

6.9 Toothed Wheel

Various spark outputs (single coil, wasted spark, coil-on-plug) are supported by Toothed Wheel, the table in
section 6.9.1 shows possible options. See section 5.3 for ignitor, coil and wiring examples.

6.9.1 Wheel combinations

| Main Wheel | Secondary Wheel | Trigger wheel arrangement | Main wheel speed | 2nd trig every rotation of |
| Non-missing tooth on crank | Single tooth on cam | Dual wheel | Crank | Cam |

6.9.3 Wheel naming

24/1. This means 24 teeth (non-missing) on one wheel and a single tooth on a second wheel.

6.9.13 Mitsubishi CAS with aftermarket disc - coil-on-plug

With the same replacement as shown in 6.9.10, both sensor outputs can be wired to allow coil-on-plug.
Set the mainboard as per section 5.2.3 and add a cam input as per section 5.2.14.2

6.18 Mitsubishi 4G63 (and Miata)

Known applications include:

• Mitsubishi 4G63 with distributorless ignition, as used in Eclipse, Galant VR4, and Lancer Evolution
• 1990-1997 Mazda MX5 Miata

The 2G 4G63 and pre-1999 Miata (MX5) use a Mitsubishi optical CAS.

Electrically, the two signals on these CAS are connected the same as a hall sensor and require a pair of pull-up
resistors in the wiring harness.

The outer track is considered to be the 'crank' signal and the inner track is the 'cam'.

See sections 5.2.3 and 5.2.14.2 for mainboard modifications.

Connect crank sensor to Tach in
Connect cam sensor to Cam in

Synopsis

Based on the relevant sections from the manual, I believe the following is an accurate synopsis. Please correct me if this is inaccurate and I'll update this post accordingly.

• The DSM CAS is an open-collector (needs a pull-up resistor) Hall sensor, and should use the pull up resistor circuit in 5.2.3 for the tach input:
  1. Find JP1 in the bottom right of the board. Place a jumper across positions 1 and 2
  2. Find J1 in the middle of the board. Place a jumper across positions 3 and 4
  3. Install a 1k resistor (any value 470R - 2k2 is likely ok) onto the pads marked R57
  4. With a small screwdriver, turn the pots, R52 and R56, 7 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.) and then turn R56 back about 2 turns clockwise.
• The cam input will duplicate the circuit for the tach input. Instructions from 5.2.14.2:
  1. JP1/pin3 should be connected with a jumper wire to a spare pin on the main DB37 connector (e.g. SPR3)
  2. Connect J1/pin1 with a jumper wire to JS10 (ensuring that nothing else is connected.)
  3. Jumper XG1 - XG2
  4. Check that R12 is a 390R to 470R resistor, replace if not.
  5. Solder wires onto a 470R 1/4W resistor and cover in heat-shrink.
  6. Connect one wire to +5V
  7. Connect the other wire to JP1/pin3 (joining the jumper wire there.)
  8. Ensure that C30 is not fitted.
• Toothed Wheel is used with the Dual Wheel trigger arrangement. 24/1 is the name of the wheel arrangement.
• Crank input is pin 24 on the DB37.
• Cam input can use any spare pin of choice, typically pin 5 or pin 6 on the DB37.
• The CAS can use pin 1 of the DB37 for a dedicated ground.
• The CAS can be powered from the same switched 12v supply for the megasquirt itself

[Matt Cramer]

You got it.

[jsdevel]

Wo0o0ot! Thanks!

[jsdevel]

I noticed recently that my crank signal periodically loses teeth and when this happens the MS wants to reset. It dawned on me that I'm currently not using shielded cable for the cam/crank signal wires.

Going back to the manual, I came across this:

Screen Shot 2017-10-02 at 1.57.40 AM.png (52.28 KiB) Viewed 2553 times

Is it necessary to shield all 4 wires going to this CAS, or can I get away with just the Crank/Cam wires? Reason I ask is that I just ordered the 22-2 shielded wire on diyautotune.com, and am wondering if I'll be good with that alone or if I should buy some braided sleeving. Here's a link to the wire I ordered for the crank/cam signal wires:

https://www.diyautotune.com/product/wir ... uge-10-39/

[tryingbe]

My friend used the shield from a coaxial cable.

http://offgridham.com/2016/04/coax-cable/

[Matt Cramer]

Can you post a composite log of when it loses sync?

[jsdevel]

My friend used the shield from a coaxial cable.

Nice! Couple of questions:

• Was he able to use the outer plastic jacket as well? I thought about braided sleeving, but didn't want it to rub against the chassy and cause a ground loop. I though about heat shrink over some braid, but thought I'd opt for DIY's 22-2 wire if it'll suffice.
• Did he pull the core from some spare coax to obtain the sheilding?
• Should I run all 4 wires (i.e. 12V, G, Crank, and Cam) inside the shielding? Or just the crank/cam?

[jsdevel]

Can you post a composite log of when it loses sync?

Unfortunately the log file I saved the data to is too large to post here (it's over 2 MB); however, I do have a few screenshots from log viewer.

Here's a sample that has a normal tooth pattern:



Here's a sample that has an abnormal tooth pattern:

[jsdevel]

I found some heat resistant shielded 22-4 wire at homedepot.com of all places http://www.homedepot.com/p/Southwire-By ... /204725191. When would it be acceptable to use the 2 wire from DIY if the manual calls for all 4 wires to be shielded?

Sent from my Nexus 6P using Tapatalk

[jsdevel]

I ended up using some 22-4 shielded wire from fry's electronics, and I put a ferrite bead on there too. I read somewhere that the ferrite on the shield can squelch noise feeding back to the MS ground.

What really helped though was fixing my LS2 coil dwell time (read more here.

You can see the ferrite in place in the attachment.

With the dwell at sane levels now, i'm no longer receiving resets. I imagine that the coils were simply starving the CAS for power which prevented it from switching to ground.