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BMW's straight six sounds gruffer in this prototype, but it offers better fuel economy and performance - to almost diesel levels - from this 3.o-litre petrol unit.

Our Verdict

BMW 3 Series
The 3 Series remains strong in the areas it has always excelled but now it's more rounded than ever

The BMW 3 Series' outstanding performance and handling complete a consummate all-rounder

What's new? Efficient dynamics is the new buzzword at BMW’s Forshungs und Innovationszentrum, or FIZ, as it’s known in Munich. It’s an extraordinary, hyper-modern research and development centre and it opened its doors recently to give us all a glimpse of the future direction for the company’s products. BMW describes Efficient Dynamics as a philosophy that will underpin the direction of its design and engineering. When creating new cars, the company says it will consider emissions, ecology, consumption and sustainability on one side of the ledger, while not losing sight of core values such as dynamics, sportiness, safety and comfort. This move towards a greener future will be achieved through incremental measures, rather than some technological big bang. BMW will have a hybrid in the future (probably with the new X5 and next-generation 7-series) but otherwise it will be making lots of relatively small steps towards eco-nirvana. The company’s here-and-now three-step engineering approach is ‘increase powertrain efficiency’, ‘intelligent management of energy flows’ and ‘weight reduction’. That might sound like techno-spin, but all of this is being built into new-generation BMWs as you read this. Weight-saving, as modest as it seems, comes from the new 335i turbocharged coupé’s thermoplastic front wings, which are 50 per cent lighter than steel (and help preserve BMW’s foundation of 50:50 weight distribution). And there’s more to come further into the future: greater use of ultra-light magnesium and carbonfibre, more efficient automatic transmissions and stop-start fuel-saving engines. Intelligent energy management is also here. The company’s straight-six engine has an electrical coolant pump, which only ‘cuts in’ when it’s needed, saving power. This will be a feature of the new Mini Cooper engine later this year. Intelligent Alternator control is also close to seeing production, working in a similar way, with the generator being ‘decoupled’ when it’s not needed. All of which adds up to eke out more miles from a gallon – improvements of between three and 15 per cent depending on the technology involved. However, the single biggest leap forward for economy comes from BMW’s new High Precision Injection direct petrol injection system, which makes its debut in the new 335i coupé. What's it like? Autocar got a sneak preview of the technology in a 330DI prototype on the roads of Munich, the production version of which is due near the end of the year. The key to the design is a new piezo injector, which fits in between the valves and deposits fuel very close to the spark plug. This is said to give a very accurate supply of fuel and very efficient combustion. The injection pressure leaps from five bar in today’s 330i to a massive 200 bar, while the compression ratio rises from 10.7:1 to 12.0:1. Most importantly, the engine runs in a ‘lean-burn’ mode unless full power is demanded. The other powerplant upgrades include new double-VANOS infinite camshaft adjustment and slightly bigger intake valves. Peak output for the new DI engine is up from 265bhp to 272bhp, although torque remains the same 232lb ft at 2750rpm. The unit also features a nitrogen dioxide trap and needs sulphur-free fuel. Although it can use ordinary unleaded, economy is reduced. A brief run around the city showed that the new engine has real bite and punch, feeling a touch more aggressive than today’s 330i unit despite the official figures. At this stage of the development there’s a subtle but clear change in engine note, too. It’s less of a turbine hum and a tad gruffer – put it down to the new injection system. On-board live fuel economy monitoring equipment showed clearly that hard acceleration hits economy more than you’d think. But our in-cabin BMW engineer’s kit demonstrated that relaxed driving in stop-start conditions would return around 40mpg – virtually the same as offered by the diesel 330d.

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