Engine Sound & Turbo

Hello!

Recently I decided to add turbo power-ups to my car game, but now I have a problem with the engine sound. Currently it works like this:

 void EngineSound ()
     {
         int gears = gearRatio.Length;
         int i;
 
         for (i = 0; i < gears; i++) {
             if (gearRatio [i] > currentSpeed) {
                 break;
             }
         }
         float gearMinValue = 0.00f;
         float gearMaxValue = 0.00f;
 
             if (i == 0) {
                 gearMinValue = 0;
             } else {
                 gearMinValue = gearRatio [i - 1];
             }
             gearMaxValue = gearRatio [i];
         
         if (started && PlayerPrefs.GetInt ("AudioIsMuted") == 0) {
             float enginePitch = ((currentSpeed - gearMinValue) / (gearMaxValue - gearMinValue)) + 1;
             GetComponent<AudioSource> ().mute = false;
             GetComponent<AudioSource> ().pitch = enginePitch;
         } else { 
             GetComponent<AudioSource> ().mute = true;
         }
     }

When the player uses a turbo power-up the top speed momentarily gets higher and the torque gets higher as well.

The problem is that whenever a turbo is used, I get the error message:

IndexOutOfRangeException: Array index is out of range. CarTouchControls.EngineSound () (at Assets/Scripts/Car/CarTouchControls.cs:264) CarTouchControls.Update () (at Assets/Scripts/Car/CarTouchControls.cs:203)

CarTouchControls.cs:264 = gearMaxValue = gearRatio [i];

CarTouchControls.cs:203 = EngineSound ();

Thanks in advance!