Need help for strange Vems laptop connection issue ????

[rossi46numberone]

Hi,
I have some  issues with my Vems laptop connection(After trying to swap the olds coils to a more recent cop's (see topic :http://www.vemssupport.com/forum/index.php/topic,1884.msg19137.html#new).
If I connect my laptop with engine running at idle for example,Vemstune work great and the gauge to, no prolblem at all,but if I begin to drive increasing the rpm and boost,Vems freeze and said " device is disconnected " at the same time the engine have some cut-off/missfire.
What is really strange,if I run without connecting the laptop the car run like a charm with no missfire but I can hear on my audio speaker some crack like electric noise with the same timing as the missfire when the laptop connected
Did I burned something else than the stepper driver?

[dnb]

Sounds silly, but are you running the laptop on its internal battery?  If not, you could be introducing a ground loop to the sensor ground.

[rossi46numberone]

Yes I use it on it's internal battery...
What I have also noticed before mounting the news coils and having all this trouble is that my lcd screen had some issue when I was increasing the rythm,boost and rpm it seems lost connection and it displays only lines and for reset it I have to turn off and on the ignition.
I was thinking about the 74HC259D fried CHIP??

[GintsK]

Is it 4-pin VAG coils? There are two grounds for each. Where secondary winding ground is connected now? I suggest to organize this connection separate and short.

Gints

[rossi46numberone]

In fact, to get a cleanest harness as possible I 've put the ground together and I fix them on the the head(cam cover) near the coils,do you think I have to reroute the trigger ground to the ecu common ground and keep the high power ground on the head??

[GintsK]

Main noise comes from secondary windings ground. My way is keep it separate from other grounds. Especially from signal ground.
In beginnings I thought that it is signal ground for coil output stage. When it was connected to VEMS signal ground car was undrivable!

[rossi46numberone]

Hi,
Job's done,trigger ground on the frame near vems support and power coil ground stay in place on the cover head.
And no change  .
At low load no problems but when I increase the rhythm  Vemstune freeze and need to be closed and restart.
I'm thinking to change the Max232 chip and the 74h259d chip to...
 

[GintsK]

What you mean under trigger ground? VAG active coils has two grounds. Where you connect them?

Power ground for VAG coils is same what is used for signal side electronics inside coil. So it should be connected where VEMS is [better not from same bolt].
If VEMS is connected to engine block or heads you still can connect secondary winding to this head. But do not use same bolt!

It is not good idea connect some engine control electronic related grounds to frame and another ones to engine due to ground shift possibility. Only exception could be mentioned secondary winding.

Another good praxis don't feed positive to ECU from same wire as ignition coils. If coils still makes lot of noise in wiring some capacitors between coil possitive and ground could help.

Gints

[rossi46numberone]

When I say trigger ground I'm talking about the signal input ground.
The 2.5m² Brown /yellow wire (power stage)on the head (I kept the original harness) and 1.5m² brown wire on the frame.
The ecu positive (+12v) is different from the coil +12v supply.
Why this didn't happens with my old passive coil
I will withdraw the ground from the frame and connect it with the Vems commons ground wires....

[GintsK]

I will withdraw the ground from the frame and connect it with the Vems commons ground wires....

keep it separate and short! I would connect them somewhere near by coils.

[rossi46numberone]

I have disconnected my lcd cable and there is a big improvement,I have practically no problem....
But what is the link of all of that

[fphil]

,but if I begin to drive increasing the rpm and boost,Vems freeze and said " device is disconnected " at the same time the engine have some cut-off/missfire.

I have shielded the serial line, and others ... and I have NOT grounded the shields at Vems but at the car body. I feel that the 5+ ground lines array out from the box are radiating much noise.
As for Vems firmware locking on a faulty RS232 line , it may be a bug. Have you reported it say to the VT bug report ?

[rossi46numberone]

Not for now because It's hard for me to explain exactly this issue...
Do you think someone believe me when I say that I heard this noise in my audio speaker  ....
Next step is trying to change the way I've grouned the ECU to see if there is some change or improvement and I will try with another RS232 cable....

Michele.

[fphil]

Useful to scope the ground signals from the box for improving cable section and earth point

[rossi46numberone]

in another word....??

Michele