This isnt the 1st time a 6 cylinder has been used in F1. These cars havent used petrol in decades, but using an ICE for racing, is mandatory IMO as well.
The 15,000 rpm limit is limiting, a V10 at 21,000rpm spunds wonderful, but a street V10(Viper) at 5500rpm and lower sounds like a UPS truck with an exhaust manifold leak.
The 80's V6 turbos were making max qualifying power of 675hp at 12,500rpm from the 1988 Honda, the Ferrari made 690hp @12,800rpm but its teh torque that made these early V6's so crazy, eventually leading to their outlaw for the 1989 season leaving the 3.4liter naturally aspirated formula.
2013 2.4l V8-18000rpm rev limit and 2014 V6-turbo 15000rpm , same track a year apart
http://www.youtube.com/watch?v=jS4Dh_EAfJI
Honda V10 screaming on dyno-The 3.0 liter V19's made between 900-930hp(BMW/Mercedes 930hp, the rest Renault, Honda, Toyota and Ferrari were around 900) For 2006 the 2.4lV6 was introduced, although the older V10 could be used for 2006/2007(with a rev limiter) by teams that couldnt buy the V8
http://www.youtube.com/watch?v=iWSt4CDNvgQ
2014 rules explained
http://www.youtube.com/watch?v=hFHmYFlbFn8