Over the last century and then some of automobile production, there have been vehicles made with all number of cylinders. Today, the most in a reasonably-high volume production vehicle is the 16-cylinder in the Bugatti Veyron. However, it took 4 turbochargers and a mass of engineering to get it to 1001 hp, and in its final form it had 1200 hp (IIRC). Yet we have Koenigsegg making four-figure horsepower cars with V8s, tuners like Hennessey making 4-figure-horsepower cars with V8s and V10s (again with forced induction), Ferrari, McLaren, and Porsche knocking on the door of 1000 hp with hybrid power trains. Speaking of McLaren, the F1 with its BMW-sourced V12 held the top highest speed record for a production car for a long while before it was taken by cars with almost twice as much horsepower.
In contrast to that, we see cars like the upcoming Ford GT making do with turbocharged V6s, and the use of lightweight yet advanced materials - much like the Koenigseggs and McLarens - will allow it to have similar performance to cars more expensive and more powerful than itself, with similar power-to-weight radios of the so-called “hypercars”. Engines are getting smaller and more powerful - the 4.0L V8 in the Bentley Continental GT far surpasses the 6.75L engines in its lesser brethren. Gasoline V10s that were ubiquitous in trucks are being supplanted by V8s, turbo V6s, and diesel in I6 and V8 configurations. Even high-volume cars that commonly came optioned with V/I6s, I5s, and I4s are relying on I4s with and without turbo (and super) charging.
So, that begs the question, how many is too many nowadays? How many will be seen as obscene and impractical in just a few years?
I know Jeremy Clarkson alluded to this not long ago with his achingly-beautiful and haunting Aston Martin Vantage V12 review, but it seems that most engines with more than 8 cylinders seem doomed for the recycling bin, to be recast into smaller, more-efficient engine sizes with fewer cylinders. Especially with 2014/2015’s most anticipated hypercars having V8s with hybrid propulsion, and companies like Tesla making strides in making all-electric vehicles outperform comparable gasoline offerings. Are V12s like Aston Martin’s, Mercedes Benz’s (and AMG's, which go into various vehicles like Paganis), BMW’s (which includes Rolls-Royce), VAG’s (in the Bentleys), and others in danger?