When planning began for the fourth generation BMW M5, there was no question it was time to boost the engine’s power beyond its predecessor’s 400 hp. The new M engine became the means to an end. In racing, 333 cubic centimetres per cylinder are considered the golden measure; in a series engine, it’s 550 ccm. If we assume 100 hp per litre of displacement is state-of-the-art for an aspirated engine, we’d be looking at five litres displacement and ten cylinders, accordingly: a rarity among engines. What further underscores the technological link to racing is that the engine blocks come from the same foundry that makes engines for Formula 1. The 507 hp, however, does not just pay homage to one of the most expensive BMW cars, it’s a nod to the US American measurement of performance. At an even 400 hp in Europe, the predecessor remained stuck on the main sales market in the USA with an equivalent of 394 SAE hp. The new M5, however, was able to get a top performance ranking in the States as it made it into the jaw-dropping 500 SAE hp range.