I am trying to make a ball rolling game, but when i use the code below the Sphere rolls slowly.

pragma strict

var tilt : Vector3 = Vector3.zero; var jumpSpeed: float = 8; var speed : float; var fuerza = 10; private var circ : float; private var previousPosition : Vector3;

@script RequireComponent(Rigidbody) function Start() { //Find the circumference of the circle so that the circle can be rotated the appropriate amount when rolling circ = 2 Mathf.PI collider.bounds.extents.x;
previousPosition = transform.position;

}

function Update () { tilt.x = -Input.acceleration.y; tilt.z = Input.acceleration.x;

 rigidbody.AddTorque (tilt * speed * Time.deltaTime);
 
 if (Input.GetKey("up"))
 rigidbody.AddTorque (Vector3(0, 0, fuerza));

if (Input.GetKey ("right")) rigidbody.AddTorque (Vector3(fuerza, 0, 0));

if (Input.GetKey ("down")) rigidbody.AddTorque (-Vector3(0, 0, fuerza));

if (Input.GetKey ("left")) rigidbody.AddTorque (-Vector3(fuerza, 0, 0));

     if (Input.GetKeyDown (KeyCode.Space)){
     rigidbody.velocity.y = jumpSpeed;
     
     
 }
 

}

function LateUpdate() { var movement : Vector3 = transform.position - previousPosition;

 movement = Vector3(movement.z,0,  -movement.x);
 
 transform.Rotate(movement / circ * 360, Space.World);
 
 previousPosition = transform.position;    
 

}

Any simple way to make the sphere roll faster? Also i cant use Rigidbody.AddForce sence I am using custom Gravity.