Ok, so it looked like the Problem had to something with the Collision. The GPU Collision Type was set at “GPU Depth Buffer” and I changed it to “GPU Distance Fields”. The emitter produced particles without beeing on the screen.
But now I have the Probllem that when I drive, stop at 0 km/h and start driving again, the particles immediatly disappear. I only happens when I stop and start driving again. I thnik this has something to do with the scripting, which is strange because when the particles where still calculated with the CPU, that problem didn’t happen.