The INNengine e-Rex is tiny and can change compression ratios in the blink of an eye. But that's just the start of what makes it different from other engines.

Today I want to show you a unique engine. It’s called the INNengine, and it claims to be a 1-stroke engine. No crankshaft, no cylinder head, 120hp naturally aspirated from just 500cc, and only 35kg.

Gearheads and faithful Jalopnik readers already know the basics of an engine's bore and stroke, but for those that might be new here, let's dip our toes in the shallow end. An engine's bore refers to ...