Complex sentence: In September 1982 Fiat added another engine to the line-up: the Panda 34 used an 843 cc water-cooled unit, derived from that in the 850.
Split into simpler sentences: In September 1982 Fiat added more engines to the line-up. The Panda 34 used an 843 cc water-cooled unit derived from that in the 850.