BMW M135i and M235i to get faster 340i motor

BMW is secretly readying two new performance flagships for its 1 Series hatch and 2 Series coupe models, according to new reports.

Bmwblog.com says the M135i hatch and M235i Coupe will both drop their 240kW/450Nm twin-scroll turbocharged 3.0-litre straight-six in favour of an all-new engine from the 340i sedan and wagon.

Sharing the same capacity and twin-scroll turbo six layout, the new engine is said to be more efficient and more powerful than the engine it replaces.

For the hatch and coupe, which are expected to be renamed the M140i and M240i, power is rumoured to increase to around 250kW while a fractional boost in the torque peak is also expected.

The option of a six-speed manual or the ZF eight-speed automatic is expected to carry over.

Currently, the M235i is capable of a very respectable 4.8-second sprint to 100km/h and, with the new engine, this is expected to fall by at least a tenth of a second, pushing the M240i closer to motoring.com.au's newly-crowned Australia’s Best Driver’s Car, the BMW M2.

That car comes with 272kW/465Nm and can hit 100km/h in just 4.5 seconds with the manual and 4.3 seconds with the seven-speed dual clutch.