Car game and simple drift system with rigidbody.velocity

I wanna make a simple car drift game. It will be like, car moves with fixed velocity in one directin and when you press the space button, it will rotate and while rotating it will drift.

But when I'm using

 car.rigidbody.velocity = car.forward.* speed;

Car rotates and moves normally, it doesn't do any drift. So how can I make this car drift and move fixed velocity?

I tried adding AddForce and AddTorque but couldn't make it with fixed velocity magnitude.

Thanks. ,I wanna make a simple car drift game. It will be like, car moves with fixed velocity in one directin and when you press the space button, it will rotate and while rotating it will drift.

But when I'm using

 car.rigidbody.velocity = car.forward.* speed;

Car rotates and moves normally, it doesn't do any drift. So how can I make this car drift and move fixed velocity?

I tried adding AddForce and AddTorque but couldn't make it with fixed velocity magnitude.

Thanks.