Increase/reset speed on tilt

Hi! So what I am trying to do is have my character go in the tilt direction at an increasing speed.If the character changes drection then the speed resets to a value and then starts increasing again.The problem I am facing is that alot of time the speed remains the same and does not increase/reset all the time.The tilt and everything else works perfectly.Here is some code and i hope you can help.Thank you.

 speed=1;
 targetspeed = 4;
 void Update()
 {
   speed = Mathf.SmoothDamp(speed, targetSpeed, ref speedDV, 0.5f);
   if(tiltright)
 {
 speed = 1,5f;
 speed = Mathf.SmoothDamp(speed, targetSpeed, ref speedDV, 0.5f);
 rigidbody2D.velocity = transform.TransformDirection(Rdirection * speed);
 }
 //same for tiltright
 }