The 170hp unit is the forerunner of a range between 1.0 and 2.5 litres aimed at bringing the brand's powertrains back into contention against VW and Ford engines technology.
It's hoped by Opel that the new engines will cut the average emissions from its cars by 27 percent, equating to a million tonnes less of CO2 over the next seven years.
New CVT and dual clutch automatic transmissions are also in development.
The Cascada, a medium-sized soft-top, goes on sale in some European markets this month.
