Whispers of Porsche's upcoming turbocharged four-cylinder boxer engine are gathering pace, with a fresh report out of Europe suggesting the engine will surface by the end of the year.
Enthusiast site flat-6news suggests that the new unit will replace the existing Boxster and Cayman six-cylinder engines, with two states of tune likely to cover entry and S variants.
Porsche is yet to confirm plans, but this latest report contrasts with earlier whispers that the turbo unit would be sold alongside the existing naturally aspirated six-cylinder units, via a new 'Turbo' range-topper.
A naturally-aspirated version is also expected in 2015 to sit beneath a new cut-price Boxster model, but the report suggests the engine will break cover in single-turbo guise.
The move would make sense: lower-capacity four-cylinder engines will enable Porsche to improve fuel efficiency and emissions beyond the improvements already extracted from the six-cylinder engines, without sacrificing performance.
A capacity of 2.5 litres is expected, and will effectively be a four-cylinder version of the aluminium 3.8 litre six found in the current 911 Carrera S.
With direct injection, Porsche's Vario Cam Plus, and the aforementioned turbocharger, outputs upwards of 261kW/488Nm are expected, which would signify a genuine step up from the existing 205kW 2.7 litre and 242kW 3.4 litre sixes.
It also remains unclear whether Porsche's dual-clutch PDK auto will be the sole transmission choice, although a healthy demand for self-shifters on the US market is likely to help the case for six-speed manual variants.
Watch for the new engine to debut at the Frankfurt Motor Show in September.