Ridge Racer Revolution on PS1: How to accelerate?

[marctv]

Hi! Thank you for this awesome project! Everything works perfectly. But today I tried out the PSX emulation. I could start Ridge Racer Revolution but was not able to accelerate. I could play the shooting game (galaga) at the beginning and select a car but I could not drive the car. Any idea? Something I have to set up? I am using 360 pads with the driver enabled.