Here’s a link to a short, accurate description of the new F1 engines.
http://www.carscoops.com/2013/06/renault-details-2014-f1-16-liter-v6.html
760 horsepower out of less than 100 cubic inches seems pretty amazing to me!
According to the article, the engine itself produces 600hp; the rest comes from the KERS.
And as impressive as either figure sounds, back in the original F1 turbo era BMW engines were making as much as 1,500hp in qualifying trim from 1.5L. Of course, with that much boost running through it, the engine was only good for about three laps.
IIRC, at the height of the turbo era for F1 they made 1200HP from a 1.5 liter engine for qualifying and raced with 900HP. The qualifying motors were good for 1 lap only at speed, leaving 1 lap for mild warm up and 1 lap for cool down.
They made sooooo much HP that the fuel was quaintly called “rocket fuel” because it was so exotic to run under so much boost pressure. I think the fuel cost back then (1980’s) was 40 dollars/gallon or so.