BMW's New Engine Bonanza

German firm banks on 500cc basis for next M3,i8 and more.

BMW’s NEW HYBRID i8 supercar launches next year and at its heart will be the world’s most powerful three-cylinder petrol engine with just 1500cc and boosted by an electric motor. This combination will pack a serious 349bhp and 2211b  ft torque. After that, a higher-revving version of the three is destined for mainstream cars like the 1-series and new Mini, as well as forming the basis for the next M3′s lightweight, blown six-cylinder.

Modular Construction, Modular Power

The three-cylinder engine is the basis of a new modular approach to BMW’s engine design, which will be the same for both petrol and diesels. The petrol three will be extended to 2.0-litre four-cylinder and 3.0-litre six-cylinder units, by adding 500cc cylinder packs. Each 500cc petrol engine cylinder can develop between 40bhp and 73.75bhp, so depending on the application the three-pot will develop between 120bhp and 221bhp, depending on the state of tune. The fours will be capable of between 160bhp and 295bhp but the most exciting possibility is a six-cylinder developing over 442bhp; that’s what we can expect from the 2014 M3 and M4 sports cars. Diesel engine cylinders will produce 27bhp to 60bhp each, adding up to the most powerful six potentially producing 360bhp.

Turbocharging – Ringing The Changes

The prototype three-cylinder engine is boosted by a single scroll turbocharger with one internal exhaust passage, but a larger twin-scroll turbo with two internal passages will be used on more powerful versions, to deliver more air and sharper response. The fours are also likely to get single twin-scroll turbos while the six-cylinder petrol engines will be equipped with twin or triple turbos. Diesel engines are likely to use either fixed or the more expensive variable-geometry turbos depending on the capacity and value of the car they are fitted to.

Efficient, Powerful, All-Alloy

Why 500cc and not 300cc or 400cc? BMW says it gives an optimum ratio between volume and surface area inside the cylinder, achieving the best combustion properties for the least amount of friction. Variable-valve timing and lift technology on petrol engines combines with direct injection to boost efficiency. BMW says the three-cylinder engine note will be closer to that of a six; expect a 220bhp, three-pot future for the Mini Cooper S. 

•  500cc cylinders form basis of new engine family, the three-cylinder being followed by a four-cylinder and a six-pot in the next couple of years.
• Petrol engines will use single scroll and twin scroll turbos, and the diesels fixed and variable geometry turbos depending on the application.
• Three-cylinder has a balancer shaft in the sump to counteract the three-cylinder engine’s natural tendency to vibrate. Engine mounts soak up the rest.
• BMW’s unique Valvetronic tech controls valve timing and lift on petrol engines, to manage airflow into engine without the need for a throttle.
• High speed direct injection on petrol and diesels gives controlof burn and is key to wringing as power as much power as possible from each engine.
• Alloy block and head are common to both petrol and diesel engines. Around 40% of the structural components are shared between petrol and diesel.