Microrusefi and wasted spark dumb coil

[Milansvk]

Hi guys, i just bought microrusefi and i am trying to connect it somehow to my car. This is my first time i work with standalone ecu and i want to learn it on my car Peugeot 106 1.4. I would like to ask you to check this ignition connection of mine that I plan to use. My car have a older dumb coil with wasted spark so i am trying to solve that how to connect it to my MicroRusefi. I chose a two transistors BU931P, mainly because of its availability and i plan to place it on some small aluminium piece (cooler). I want to connect pins 9-12 and 10-11 together (cylinder 1-4 and 2-3) to achieve effect of wasted spark ignition like on my scheme. What you think about that connection please? Is it safe for Microrusefi board? Do you recommend to add some other components to this wiring? Thank you for help!

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[AndreyB]

No reason to connect four outputs - just tell rusEFI you are running wasted spark and use only two outputs.

[AndreyB]

PS: https://github.com/rusefi/rusefi/wiki/Discord

[Milansvk]

Yes i found that setting for wasted spark. Transistors just arrived so i try it. Thank you very much

[Milansvk]

Yes i found that setting for wasted spark. Transistors just arrived so i try it. Thank you very much!

[Milansvk]

Hi guys. So today I tried to start the car on the rusefi ecu for the first time. The car started beautifully but unfortunately after a few seconds the engine died and wouldn't start again. I found out that the ignition transistors were burnt out. They were completely hot to the touch and after some measurements I found out that a diode inside had probably blown in them. Can anyone please advise me why they overheated so much just a few seconds after starting the engine? I placed them on small aluminum coolers so that both transistors are isolated from each other as you can see in the photo.

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I don't want to believe that this is caused by small radiators because it didn't happen at high speeds but after about 5 seconds of idling. Or should both transistors be placed on a common radiator which would essentially connect the collectors? I don't think that would do any good, or?

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. Maybe I made some stupid mistake but I would like to avoid burning more transistors so I prefer to ask more experienced people

[kb1gtt]

I suspect transistor was not expected. You likely had excessive drive current. Most setup these days use protected MOSFETs.bwhich have next to no drive current they trigger with voltage. I don't know you schematic but that's my guess with a blindfold on.

[Milansvk]

Ok second try. Now i bought igbt stgw40v60df which should hold 600V and 80A. Its controled by 12v so i have to use driver tc4420 driver to control that igbt. Used big heat sink and both igbts are isolated from heat sink.

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Now car runs for maybe 20 minutes. I was playing with VE map and suddenly i saw smoke from ignition coil and now car runs only on two cylinders. I used dwell of 3.4ms same like stock ecu. I dont know why this happend but I'm tired of constantly burning components so now i want to buy 032 905 106 which is smart wasted spark coil used in VAG. I hope it will run and dont get burn

[Dron_Gus]

To drive 'dump' coils you need specialized IGBT/MOSFET or extrernal zener diode(s) for overvoltage protection.

[Dron_Gus]

Or you can use some OEM "ignitor"

[Milansvk]

Hmmm interesting. Till now dont seen anything like this. Thank for info i am going to look at it on google.

[Milansvk]

So today i installed Vag smart coil 032 905 106. Till now car runs fine but i measured control signal to the coil on running engine with oscilloscope and it is only 3.6V instead of 5V. Cannot that be the problem and cause coil ignitor overheat and damage if igbts dont switch fully? Somebody have idea why i measured only 3.6V or is it normal?

[kb1gtt]

J701 is a older school but reasonably low cost and solid option. eBay is ~$20 USD for a J701.

[Dron_Gus]

So today i installed Vag smart coil 032 905 106. Till now car runs fine but i measured control signal to the coil on running engine with oscilloscope and it is only 3.6V instead of 5V. Cannot that be the problem and cause coil ignitor overheat and damage if igbts dont switch fully? Somebody have idea why i measured only 3.6V or is it normal?

Some VAG coils are known to consume high current over logical input. You can try lowering R122-R125 serial (limiting) resistor on MRE's IGN outputs. Try changing to 47R or even 33R.

[Dron_Gus]

Some VAG coils are known to consume high current over logical input. You can try lowering R122-R125 serial (limiting) resistor on MRE's IGN outputs. Try changing to 47R or even 33R.

Just checked your partnumber... I was thinking you are using some coil-on-plug.
Not sure if this one need lower serial resistor. But if you have oscilloscope you can check it using current shunt. Check how fast does it opens.

[Milansvk]

So i measured trigger signal to ignition coil with disconnected coil and get nice 5V. When i checked some waveforms on youtube and google i seen that they have ussualy 4V so it looks normal and i am not goint deal with it anymore. So that Vag coil looks like best and cheapest option in case you have not space for COP coils. Till now it works perfectly. Thanks to everybody for help guys.

[Tommynwn]

3.4ms

Fun fact: i have a 206 1.4 with the same coil, works pretty well with the bosch ignition module, also now running on 3040D mosfets like charm
The default dwell of this coil are 1.6 to 1.8ms, 1.7 at idle generally, going less than 1.1 produces missfires, going higher than 2.4 also produces misfires and overheat of the coil, take care

Ah if you have the 1.4 tu3jp KFX variant, it runs at very low advance, take care of the knocks, idles at 4º, knocks at 12º at 3000rpm, you never seen more than 28º on this engine, probably gonna share some advance tables pulled from the distributor model (1991) when i test the car