In all of its glorious itty-bitty detail.
Admittedly, there isn’t much competition for anyone looking for a record title involving W18 engines, as there have been very few of them ever built. There were a few aircraft engines in the Thirties, one F1 prototype, and a few Bugatti concepts in the Nineties. Although it should be noted that the configuration is different from Bugatti’s current W16 engine, which uses two narrow-angle V8s that share a common crankshaft. This is just three banks of six cylinders.
The following video shows a fantastically tiny working model of a W18 built by hand and then running. It’s something truly amazing.