Porsche is working on a new four-cylinder petrol engine that would power its new baby roadster, the Boxster, the Cayman and potentially even the 911, the firm has confirmed.

Outgoing head of R&D Wolfgang Durheimer said at the Detroit show: “We have a four-cylinder boxer engine under development.” He admitted that the unit “can be applied” to the Boxster and Cayman. Porsche had been expected to introduce a four-cylinder powerplant on its forthcoming small roadster, which shares underpinnings and parts with the VW Bluesport and a sister car from Audi.

But Autocar now understands that Porsche has won an internal argument to get its own powerplant for the car. Sources say the flat four motor is 2.5 litres and has been producing around 360bhp in turbocharged form. Durheimer said the unit “could be applied if necessary to the 911. Our decision is, on the 911 side, we’ll stay with the flat [six]. But there are opportunities for the future.”