The head of engine development at Mercedes-AMG says there’s “more to come” from Affalterbach’s new turbocharged 2,0-litre, four-cylinder petrol engine.

The newly developed M139 engine, which will churn out a whopping 310 kW and 500 N.m in the upcoming A45 S (and a still impressive 285 kW/480 N.m in the standard A45), is billed as the world’s most powerful series production four-cylinder unit.

Ralph Illenberger, head of engine development at Mercedes-AMG, suggested to motoring.com.au the powerplant had even more to give.

“There will be more to come,” Illenberger told the Australian publication. “There’s always room for improvement. But [310 kW] is really quite a high number, especially when it’s also street-legal.

“That was the challenge. We’ll see what the future will bring,” he said.

Illenberger added the more powerful new engine also boasted better throttle response and suffered from less turbo lag than its M133 forebear.

“The torque curve is improved. The old one was flat and like a diesel. The new one offers more torque at lower r/min– it’s no longer flat, but shaped,” he said.

“There’s pretty good acceleration at 1 500 r/min. Acceleration at 3 500 r/min is much better. You’ll notice improved driveability and it revs further, too.”

The new engine will debut in the A45 hot hatch, before being rolled out to the likes of the A45 Sedan and CLA45, too (rumours of a GLB45 have also already started).