How to hide a car until it appears?



I have 253 frames. I would like to have a car come up a slope. Due to the slope the car is not visible in the first frames, only say from the 50th frame. I have modeled the scene so I can have a camera projection.

My question is: how can I hide the car in the first frames (alpha as well) so that it only becomes visible after a while. I don’t want to mask the car out in post.

I am using v-ray for maya. Any help would be appreciated. Thanks.

By the way: When I turn on hold-out my mesh turns gray. I can still see my car through my mesh in the render.