On the test track screen sometimes when clicking the speed multiplyer quickly the rpms UI will spin around crazily and so does the sound. When you turn the multiplyer back down to normal there is no sound, only wind / road noise. Seems to happen with higher rpm cars but that could just be coincidence.
That’s because it thinks the engine blows up. Happens on most engines. Don’t know if it’s still there, but the secondary rpm gauge (not the big tacho) used to go into negative, then display NaN.