Chronal Engine — Greg Leitich Smith

When Max, Kyle, and Emma are sent to live with their reclusive grandfather, they think he's crazy, especially when he tells them about his time machine. But after Emma is kidnapped at the exact time that her grandfather predicted, Max and Kyle are forced to believe his eccentric stories -- even the one about the Chronal Engine in the basement.

Now, to save Emma, Max, Kyle, and their new friend Petra must pile into a VW Bug, and use the Chronal Engine to take the road trip of a lifetime -- right back to the Cretaceous period. With dangers all around, the teens find themselves dodging car-crushing herbivores in addition to the terrifying T. rex. In this ancient environment, can three contemporary teens hunt down a kidnapper, forage for food, and survive long enough to return home?