[AlecBarwa-Bosco]

Hi all,
So I've been trying to figure this one out for a week now. I have an extra spark discharging when I stop cranking or when I turn off test mode in tunerstudio.

Because of this I have not tried to start the car yet because of the backfire I'd likely get through my intake manifold.

I have tried different spark settings, hi or low, no change. Tried different dwell times.
I even tried with coils unplugged and you can see the ignition channel LEDs on the board still light up one more time once I stop cranking.
Again, it does this both when cranking and turning off test mode. One extra spark.
I'm using Mazda wastespark smart coils from MX5/323 "going low" running dwell 3ms, cranking dwell 4.5ms, spark duration 1ms, as a timing only set-up.
Want to sort this before I go trying to start the car.
Below is an image of the log.
I'll also try uploading a file of the log and the tune.
Running firmware 202103 on a 0.4.4c board

Cheers

[theonewithin]

No log. No tune.

Without those expect no help.

[AlecBarwa-Bosco]

No log. No tune.

Without those expect no help.

trying my best mate, I said I would and here they are........just didn't have access to my laptop yet.

[theonewithin]

You understand that the engine continues to rotate after letting go of starter yes?

It's pretty normal for an ECU to think that when the engine slows and it see's what it thinks is a missing tooth, that it will fire ignition/injectors.

Nothing you can do about this.

[AlecBarwa-Bosco]

You understand that the engine continues to rotate after letting go of starter yes?

It's pretty normal for an ECU to think that when the engine slows and it see's what it thinks is a missing tooth, that it will fire ignition/injectors.

Nothing you can do about this.

Very aware of that, but it does it in hardware test mode as well. Hence my concern. Its also not in rhythm with the motor, there is a delay, more than just the motor slowing down. I can clearly hear the motor stop and then "spark".
And in Hardware Test mode in Tunerstudio there is no rotating motor......yet it still does it, Briefly after pressing the 'off' button

[PSIG]

Not a problem in the real-world, as when you key-off, the power to Speeduino (and everything else) also stops.

What you are seeing is "normal", where the dwell periods are already calculated in-preparation for the next firings, and Speeduino remains powered. Although there is no firing signal output, if dwell is occurring, then a loss of signal is effectively a spark signal. The same "after-spark" occurs if coils are dwelling and power is removed from the coils, e.g., key-off and coil relay de-energizes.

Here is an old video of testing a new VR conditioner design, for others to see the effect you are describing:
https://efistuff.orgfree.com/PostHost/V ... R-v1FR.mp4

[AlecBarwa-Bosco]

Righto, thankyou for clearing that up. That's quite interesting.
Hopefully it doesn't cause me a nasty backfire. It might be an issue for me as I run LPG which is a vapour fuel mixed with the air at the throttle body, so the plenum is full of it.
I'll find out tonight when I get home from work I suppose
Cheers

[NickZ]

Ive been running on speeduino and many board designs for the last 4 years and have never experienced it on a real engine, maybe its just your setup is wrong somewhere.

[AlecBarwa-Bosco]

That's the assumption, I thought I must have something wired up wrong or dead coil igniters (still possible really). But I tried swapping coils, and I tried removing and checking all coil wiring and it still does it (even with coils and wiring disconnected). Wired up exactly as it should be according to the manual. And I chose the coils I chose because they were from an MX5 and I figured with lots of MX5 users running speeduino it would be a good match.
After all this and trying to figure it out on my own I thought I'd ask if it's happened to someone else.
My thought is I've done something wrong in the tune, but I haven't changed that much from the base tune.

[TasosVL]

Did you got it resovled? It happens to me too and it backfires when the motor stops rotating, after i let go the crank button.