Let's see if the mt.net collective can help me with a little something... I have built several ECU stims, much like this one... ...to test all the ECUs I send out of the door. It dawned to me at some point that I can use these with the stock ECUs, and with the use of a scope, I can extract very useful information (ignition timing, ignition dwell, cranking pulsewidth, IAT/CLT corrections, IAC valve %, etc). So I modified my 90-93 1.6 stim to use on a 90-93 ECU. I got excited when it actually synced and got spark and fuel on the stim, only to lose fuel a little later. In other words: 1) I power it up 2) I get spark 3) I get fuel 4) After 16 injector pulses, it stops injecting (the LEDs go off). So I'm trying to figure out why. Here is a list of what is actually connected to the ECU on this stim: 1) Constant +12V 2) Switched +12V 3) Spark output for cylinders 1&4 4) Spark output for cylinders 2&3 5) A/C relay LED indication (ie if the A/C is actually active) 6) P/S input (through a jumper) 7) A/C thermo switch (ie A/C button) 8) Cooling fan LED indication 9) Clutch/neutral switch input 10) All grounds 11) CAS input (crank+cam) 12) TPS as per the stock TPS sensor: 1N is +12V, 2L is +5V, 0% TPS grounds the 12V, 100% TPS grounds the 5V, 1-99% leaves both floating. 13) Coolant sensor (potentiometer, only two legs connected) 14) Air temp sensor (potentiometer, only two legs connected) 15) AFM (5V potentiometer, all 3 legs connected) 16) Idle valve (LED) 17) Injectors 1/3, 2/4 18) ST SIGN input I haven't connected: a) Check engine light (1E) b) Diagnostic connector wires that go to 1D, 1F and 1K c) Stop light switch (1O) d) Heater control unit (1S) e) Tail fuse (1U) f) Short connector (2H, present on Cali ECUs only?) g) Input from igniter module (2I) h) O2 sensor i) Purge solenoid valve Any ideas?

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Plug and Play Megasquirt ECUs for ANY 90-05 Miata (NA, NB1, NB2 w/VVT, MSM), including basemaps to get you started ASAP. PM me for details.

Not a clue, but this is freaking cool!

Could it be that the stim doesn't perfectly replicate the CAS signals and the ECU just loses sync?

Might be worth hooking up an actual CAS to rule that out?

i wouldn't think that. I can drive a MS by just power ground and CAS.

My bets on g and h.
ECU not knowing what the ignitor and AFR's are up to.
Maybe

An ECU will run without the O2 sensor. I've never tried it without the IGf pin connected, but that would be my guess.

Parallel the spark outputs (you might need diode isolation) and send them back into that input.

I just tried that, no go. It appears IGf is 12V high, and needs to be pulled down, so I need to get a transistor in there to pull IGf to ground on each ignition pulse.

Yup, the transistor did the trick!

So two immediate notes so far:

1) The stock ECU on the batch injection 1.6 will fire ALL injectors simultaneously while cranking - ie while it receives the cranking signal on pin 1C.
2) If the stock ECU does not receive ignition pulses back from the igniter module through IGf for 16 NE events, it stops all injection events to protect the engine from flooding and/or destroying the cat. In other words, if your igniter is fried, you will also not get fuel after cranking for a while.

Again, well done mt.net!

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Plug and Play Megasquirt ECUs for ANY 90-05 Miata (NA, NB1, NB2 w/VVT, MSM), including basemaps to get you started ASAP. PM me for details.

Well done Demitris too.

<Wonders if the MegaSquirt coders would be willing to add simultaneous injection during cranking events to the MS code>

At least that explains why the OEM ECU cranks and fires so quickly compared to the MS.

Oh, many more surprises to come:

Cranking dwell at 0degC. 50ms. Yes. Fifty milliseconds! Does not change with voltage, and is only so during cranking (ie ST SIGN is on).

Yowzer!

Can we replicate that on the MS?

Might fix my complete refusal to start when below freezing.

Looking forward to a complete ignition timing table!

Are you going to stim all the year ECU's? This is fascinating...

So far I've got a 90-93, 94-95, waiting for a 96-97, I have a complete harness for a 99-00 (waiting for the 99-00 ECU, immobilizer + keys to arrive) and I also have my own 01-05 ECU, immo and keys. So yes I am going to try and stim them all. I do have all the stims for these years, I just need to mod them so that will work properly with the stock ECUs (much like this 90-93 stim).

I'm afraid it will get significantly more difficult with the 99-05 ECUs. I have no idea how they will react to all the things missing (EGR valves, purge valves, etc) and whether or not the data collected will be skewed or not.

Getting the ignition timing on the stim manually might be a little difficult - I may have to rig something to measure it automagically and report it on a small LCD.

__________________

Plug and Play Megasquirt ECUs for ANY 90-05 Miata (NA, NB1, NB2 w/VVT, MSM), including basemaps to get you started ASAP. PM me for details.

If your cranking settings are based on the DIYAutoTune basemaps, then that would explain it. It is actually quite off compared to the stock ECU, below 30*C.

My settings *are* the DUY basemaps

Do you have anymore data on it then I can plumb it in?

Thanks!!

I need to get the data out first - there is MASSIVE information to be had from this ECU alone.

i want to know the timing differences with and without a/c

0.

Interesting notes about the cranking dwell

interesting. thanks.

Hope you have a 94+ euro 1.6 ECU to work on as well

On a different note, the stock 2002 is manipulating the idle using the ignition advance - with a timing light you can see the white dots drifting left and right, while jumping GND to TEN makes the timing solid.