Matt Cramer

GM ICMs use their own weird crank trigger pattern. I don't recommend adapting them to other engines in most cases. You could, however, gut one and direct drive the coils: https://www.diyautotune.com/support/tech/customer/gm-dis/

For those wondering why the trigger wheel has a bit of a weird pattern, here's what is going on. We had the following goals when putting together the trigger disc. 1. Improve timing accuracy 2. Allow distributorless ignition conversions using the stock trigger wheel. 3. Support the existing MS1/Extra through MS3 wheel decoders. 4. Allow working with existing MegaSquirt L28 installs with no changes to wiring or modifications inside ECU. 5. Support 4, 6, and 8 cylinder engines. Nissan (and several others!) used a few optical pickups across a very wide lineup. 6. Allow sequential injection for MS3. 7. If possible, allow the engine to start within one crankshaft revolution. Goal #7 meant the trigger wheel pattern needed to use the same pattern repeated twice every 180 degrees, with the ECU set up for a wheel spinning at crank speed. Keeping #4 in mind, that also meant a pattern that used just one sensor since existing installs would be set up that way. So there is a pattern with two missing teeth 180 degrees apart, and the ECU interprets that as a crank wheel because the pattern repeats once every crank revolution. We then added in a one tooth "cam" pattern to allow sequential injection.

You're best off just wiring the VSS straight to the speedometer.

If you rework the front accessory drive to use a timing belt instead of a V-belt and select your pulley ratios carefully, this could work... but that seems like WAY more work than any other trigger arrangement I could possibly imagine

The kits look good, but I'm a bit concerned about PLA's ability to stand up to underhood temperatures. Have you considered making them in aluminum?

Check the voltage on the LC-2 analog output wire - is it within spec?

Cam signal looks fine to me.

You may need to adjust the trim pots. Can you post a composite log of what signal you're getting now, and a copy of your MSQ?

What sort of cam sensor are you using?

Normally this would be used in combination with a missing tooth crank wheel to determine engine phase. The sensor can trigger just about anywhere except lined up with the missing tooth.

We've used EGTs for evalutaing per cylinder fuel, but not timing. With the timing, we just used the dyno to see if changing each cylinder made a difference in power.

That log is a special purpose log for RPM input, which seems to be having a bit of trouble. If you are using a VR sensor, try swapping Ignition Input Capture. It does not show much about other factors, but you need to fix this first.

Also, if you can post a copy of your tune file and a data log of how it's doing on the current settings, this will be very helpful.

It's a pretty common application. We have some notes for a regular MS2 here. https://www.diyautotune.com/support/tech/install/chevrolet-gm/megasquirt-your-sbc-v8/ Another option if you don't already have the MS2 would be to use a DIYPNP, which plugs into the stock harness once you assemble it.

Ones that are wired straight to the ECU are usually a safe bet. I'm not sure which ones are easily transplanted, though.

I used a cheap parts store Sunpro on a build that never had a tach to start with, driven off an MS3-Pro tach output. It worked excellent.

Can you send me a link to what documentation you're referring to? I checked our documentation and I do not see any point where we state there are sync issues with the stock CAS. The new trigger disc's benefits are (1) improved spark accuracy when using MS2 and (2) cylinder identification. MS1 and MS2 do not use the outer ring of 360 slits, and never supported this. Both of these only used the inner six slots, from the first "Mobythevan" install to the current code. There were a few experimental attempts to use the 360 slot ring on MS1 and MS2, but they didn't pan out - Nissan used purpose built hardware to handle the high resolution ring, but all the attempts I've seen were code-only and did not attempt to address this. The DIY ring adds cylinder identification and improves spark accuracy over the factory ring. MS3 can read the high res wheel but needs to be coded for the specific inner pattern. Currently we have the RWD SR20DET, VG30DE / RB, and GM Optispark patterns coded; the "One long and the others short" is not coded. The 360 slits are used during cranking and at 1000 RPM or below, and then it uses only the inner slots - we did this based on information about how many of the factory ECUs handled the 360 slits. Early implementations of this code had a bug - the thread you linked to is one such example. The issue was corrected in MS3 V1.3.3 firmware and we have not seen any indication of it re-surfacing in subsequent releases.

Pretty much EVERY MS2 firmware out there will support the factory trigger disc - I'm not aware of any that don't - and any firmware released in the past 6 years or so will support our trigger disc. 3.3.0 can use either one no problem.

Looks like I need to clear up a few things here. MS2 can use the stock CAS no problem if you are using it for a distributor. It does not use the 360 slits, only the inner six slits. This works for "Basic Trigger" mode and will let you control the timing. Basic Trigger mode is for letting the MS2 control timing on a basic distributor (one pulse per ignition event) with locked out timing. If the coil is firing, but the timing is not advancing, check to be sure that (1) you don't have Fixed Angle selected, and (2) you have the correct spark output (JS10 vs D14) selected to match how your board is built. Yes, the stock distributor disc does have a few limitations, which we created the drop in disc to solve. Here are the limitations: 1. The six slits trigger a fairly long way before the spark fires, which costs you a bit of timing accuracy, especially when cranking. (You can generally tune around "starter kick back" issues while cranking by running less cranking timing, but there's still room for improvement). 2. There's no cylinder identification, so it won't support sequential injection (note that an MS2 can't do this on a six cylinder anyway) or distributorless ignition (which the MS2 can do if it has the right signal). So, upgrading the trigger disc can give you a few improvements - but you don't need it to get your engine up and running.

The main question isn't what mods are on the engine - it's what features you need the ECU to have, whether it's traction control, plug and play installation, onboard data logging, boost by speed, etc.

Realistically, anything that'll run Windows XP or later will work with TunerStudio.

And those numbers are a fairly typical range for an MS2 or MS3.

Are you using low or high impedance injectors?

D14 is a processor controlled output and it depends on what you've set to trigger D14. Please post your MSQ file.

Actually, the distributor's optical sensor will short the resistor to ground. I'd use 1/4 watt for reliability.