Cummins engines have earned a bit of a cult following over the decades — and for good reason. In the U.S., they're the iron workhorses found in everything from pickup trucks to massive semis, and they ...

Both Cummins and Ford offer 6.7-liter diesel engines. They share a few similarities, but those don't go much further than their displacements.

The Nano Bee, created by engineer Ronald Valentine, is a diesel engine smaller than a quarter but powerful enough to to spin a model-plane propeller.