Haven't you always felt like you knew, but deep down, you really had no idea? Join the club.
And with all due respect to tuners like John Hennessey, who perpetually redefines the limits of what a street legal Chevy V8 can do without turning into an expensive grenade, it's several rungs up the difficulty ladder to make every aspect of a car right down to the engine. We wanted to know who actually makes the most powerful engines in the world, so we eliminated companies like Pagani, who use Mercedes motors, and even Aston Martin, whose beautiful V12 is essentially two Ford V6s mated together. What's left, then, is this list of nine manufacturers, all of whom legitimately build their own really, really powerful engines.