My RC car does not delay after setting the motor speed:
void avancer()
{
motor_speed2(motor_A,20);
motor_speed2(motor_B,25);
[glow] delay(1000);
[/glow]}
I'm pretty sure your Arduino-driven car will be more responsive if you don't do this, either.
What do the two hard-coded values (20 and 25) mean? What does the motor_speed2 function do?