GM HEI computer controlled distributor

[Machismo]

Grounding the ferrite/iron of the coil is fine as long as it is also connected to engine head to close the loop between point of spark and return current to coil secondary.

Hi,

I think I mixed the grounding thing in my head when I said that primary and secondary coils are grounded to the same point. They are not and I think such a grounding would not be even possible. It's the 'floating' ferrite that is grounded to the same point, like you said. 
The black wire is the secondary coil ground and the 'spark output' at the bottom is the other end. Resistance 8kohm.
Primary coil's other end is the red wire +12v feed and negative yellow wire C- that comes from the IGBT. Resistance 0.4 ohm.

The black wire was grounded to the engine and today I changed it to frame. No difference in the serial connection quality, it still freezes every now and then, and much more if I rev the engine.

I added two more 1000uf caps between the 12v and black wire. Now the multimeter showed under 0.1V on ac so it is 'perfect' but it made no difference.

I'm starting to be out of ideas how to reduce the noise further? The battery, frame, engine and the alternator are very well grounded too, I've connected them all with new thick wires.

What about moving IGBT out of the board to right next to ignition coil?

[fphil]

All is well you might think? Not quite. The engine runs but there are huge problems with the laptop serial connection. It's now disconnecting all the time.

What about checking/scoping the RS232 connection first + terminal parameters? Do you use a ground line?

[Machismo]

What about checking/scoping the RS232 connection first + terminal parameters? Do you use a ground line?

I'm not familiar with terminal parameter testing? I use a ground line (the third wire). I changed the Fifo buffer size sliders to minimum from windows com port settings and it once again made it work a bit better. Now it is quite good, but still not 100%.
I checked it from both wires and also in both the data waveform looked like identical when the car was running and when it was not. So there were no spikes generated in the signal by the running engine.

The other wire's data pattern looked like this and was mostly the same all the time.



On the other you could see the data flowing. Here you can also see the actual problem, everytime the signal suddenly disappears on scope, the vemstune display also freezes.



Windows Com port and Vemstune is set to 57600 baudrate, I also tried 19200 but it did not work perfect either. Is it possible that board is somehow cutting the connection? I can't image it is my laptop, I run it on battery so there are no charger related problems either.

[fphil]

It looks like the link gets out of sync. Have you tried without ground line?, 2 are enough most of the time. 19200 is good for my setup. VT has a "Preference/Communication settings" menu.
You did not say if you get good connection engine not running.

[Machismo]

Ok, I will try without a ground line, never thought of that. It works perfectly when the engine is not running and it worked also with engine running before I installed the IGBT.

[Machismo]

After disconnecting the ground line, the connection did not work at all. Then I put 100 ohm resistor as groundline, it worked like solid wire, but no better. Finally I tried another laptop also with native com port, but it also acted the same.

My conclusion is that there must be a somekind of an internal ignition noise in the board... The serial connecting is the only thing that suffers from the noise, since everything else works and also the vr trigger works perfectly to the redline.

Any more tricks that come to mind?

[fphil]

what about to scope this ground line  / the common genboard ground line  / battery ... ?