BMW M135i and M235i set for more powerful, less thirsty engines

Major engine enhancements to BMW's entry-level M Performance models will arrive before the end of the year.

The Bavarian brand says it will "pass the baton" from the existing turbocharged six-cylinder engines powering M135i and M235i models to the typically more powerful and less thirsty new engine that will launch in models dubbed M140i and M240i.

The upgrade affects three models in Australia: the M135i five-door hatch, M235i coupe and M235i convertible.

The power boost is backed by a 7 per cent drop in fuel use, with the claimed official consumption now down to 7.9L/100km. As is becoming the norm with most makers, performance increases despite the engines being less thirsty.

In this case 0-100km/h times are down to 4.6 seconds using the eight-speed auto that is already on M Performance models here. The convertible's extra mass adds 0.1 second.

Power increases from the current 240kW/450Nm to 250kW/500Nm — incredibly, that matches the figures of the bahn-storming 1 Series M coupe cult car built in 2011-12.

That car has only now been superseded by the M2 coupe, which can run to 100km/h in just 4.3 seconds, thanks to outputs of 262kW/465Nm, trick componentry and weight-saving measures.

Prices for the existing M Performance models start at $62,900 for the M135i and top out at $86,500 for the M235i convertible.

There is still a big market that appreciates a good engine without wanting to engage every day with a full-on M model.

Expect minor increases across the range, given the engine updates are likely to be backed by refreshed fenders and features.

BMW Australia spokeswoman Lenore Fletcher says the new powertrain should fuel already strong local demand for the company's performance variants.

"We don't have any specifics other than the release at this point but we do know Australians will welcome the added performance," she says.

"Until the arrival of the M2 the M135i and M235i models were our go-to hot hatch and fast coupe respectively and there is still a big market that appreciates a good engine without wanting to engage every day with a full-on M model."

The gear ratios in the eight-speed auto have been stretched to match the extra power.

Drivers can choose to perform multiple downshifts on the paddle-shifters when entering a corner, with the car then matching ratios to revs as they drop.

Left in auto mode, the transmission can employ predictive shifting — checking with the satnav to match ratios with the contours of the road.