Bad Piggies Ground Hog Day Bonus Level 1-IV (1-4) is 3-starred in two steps. First, navigate your contraption all the way in the tunnel, through the star box. Detonate the tnt to send the pig to the finish line above. Finally, using the same contraction, you want to detonate the tnt just after passing the second hill. That should send the pig flying high towards the finish line within the time limit.
If you have a different strategy for completing this level feel free to leave a comment below.