I agree with Hoogle here, I think the difference needs to be more pronounced.
When I first landed on the image I thought it was just a photo that had been over-shopped, and it took me a second to realize the drawing-to-reality transition.
Personally, I don't think the transition needs to be particularly sudden, but I'd make it more pronounced by accentuating the drawn look, like in IamSam's version, where it's just a line sketch.
This way you could transition that into your effect, and then finally into the original photo. This would make it a softer transition, making the transformation look more natural, but the effect would be more obvious as the starting/end points would be so distinct from one another.
Another cool idea could be to start the drawn side as a blueprint, where you knock out some of the background details and implement a grid,ruler markings etc... and then move from this much flatter state to the realistic part of the image where the car will seem to be almost lifting off the page by comparison.
Nice work though, I'm interested to see where you can take this.