If even the screens black out then there is massive EMI. 

First thing to check is that you use resistorized spark plugs. Non-resistorized spark plugs can be incredibly noisy. Other than that, you should ground the car (to earth ground) and need to look into shielding of cables. You should also ground the chassis of the dyno and the chassis of the YourDyno box. Make sure shields are connected to earth ground on one side only (or you get ground loops). 

A powered USB isolator that can help too, for example  USB Isolator for Protection of all types of USB devices (usconverters.com)

Thanks for quick help.

Problem is that this vintage magnetos need no resistor plugs and cooper wires.

It an engine dyno. The electronic is outside dyno room one monitor is inside. Load cell, motortemp and oilpressure the wires that go in to the engine room.

I will shield them  https://www.techflex.org/de/verzinntes-kupfer-geflecht-tinned-copper.html and see what happen.

The PC is still working when motor is running but YouDyno software is frozen same moment that motor is running

Did you check if the engine runs fine on resistorized spark plugs? 

There are some general EMI troubleshooting guides here, not made for YourDyno but valid still: DYNOmite Dynamometer (dynomitedyno.com)

yes I now that but I was a little afraid about the coil of this rare vintage magneto.

I will screen the cable and distributor like in Gen2 Corvette and try again

I used screened cabels now on all sensor wires and for stepper motor.

It comes muuuch better but the main problem I think is the monitor port to HDMI adapter. After I covert with alu foil and grund it is nearly gone.

I will now cover the HDMI cable and adapter comlete https://www.techflex.org/de/verzinntes-kupfer-geflecht-tinned-copper.html and try again