Complex sentence: Although the engine developed 80 bhp at 11000rpm and 160 bhp per litre, the idea was abandoned, and subsequently, in 1972, Formula 1 rules were changed to outlaw the use of engines with more than 12 cylinders.
Split into simpler sentences: Although the engine developed 80 bhp at 11,000 rpm and 160 bhp per litre, the idea was abandoned. Subsequently in 1972 Formula 1 rules were changed to outlaw the use of engines with more than 12 cylinders.