The 206 will have a 68bhp unit, which produces 112g/km of CO2, and can reach 0-60mph in 15 seconds, with a top speed of 102mph.
The 307 version has a 70bhp unit and produces 120g/km of CO2, while offering 0-60mph in 16.3 seconds (16.5 for the five-door) and a top speed of 102mph.
Engineers have created a unit which weighs 98kg, some 50kg less than the 1.9-litre engine it replaces. It is available on the 206 Style, Eco and LX models (three and five-door) and on the 307 Style three and five-door and LX five-door.
Prices start at £8,895 for the 206 and £11,560 for the Style, with first deliveries expected during December and January.