BMW unveils biturbo 3.0-litre six with the same power and more torque than the 4.0-litre eight cylinder engine
February 20, 2006 Backing up its global success with the innovative 507 bhp V10 powerplant for the M5 and M6 super cars (2005 Engine of the Year), and the VALVETRONIC magnesium-aluminium straight-six engines introduced in 2005, BMW is set to tear the wraps off a production-ready biturbo version of its acclaimed petrol-powered six-cylinder. Retaining the familiar 3.0-litre capacity, the new all-aluminium engine boasts a pair of turbochargers, each feeding a trio of cylinders. When combined with the efficiency and flexibility of acclaimed BMW VALVETRONIC and double-VANOS technology, the new engine is able to produce an immense 225 kW of power and 400 Nm of torque. BMW claims that with the technologies it has employed in the new motor, the traditional bugbear of turbo lag has been vaporised and fuel consumption has been slashed.
The new engine is armed with a Table Mountain-like torque profile that defies the term curve. Peak torque of 400 Nm is delivered between 1,500 rpm and 5,800 rpm and the engine boasts a 7,000 rpm red line. The biturbo six-cylinder has the same power and more torque than the muscular 4.0-litre V8 engine fitted to the 740i. However, in keeping with BMW philosophy, the substantially enhanced performance does not come at a substantial cost to the environment.
Fuel consumption, previously a bug-bear of high-performance turbo-charged engines, has been radically reduced thanks to high-precision direct petrol injection, used for the first time on a BMW six-cylinder motor. The V12 powered BMW 760i/Li features direct petrol injection for its 6.0-litre engine.
A further traditional turbo-engine wrinkle has been ironed out by BMW engineers: turbo lag. In the new engine, this has been completely removed, thanks to low inertia turbochargers. The driver need only brush the accelerator pedal to receive an immediate surge of power and performance, as the engine delivers an electrifying response according to BMW's press information.
While turbocharger technology is almost as old as the internal combustion engine itself, in combination with cutting-edge high-precision direct petrol injection technology BMW engineers were able to write a new and exciting chapter in the history of forced-induction.
The foundation for all this power and torque is drawn from the exemplary characteristics of the magnesium-aluminium 3.0-litre engine which is rated at 195 kW (as fitted to the BMW 130i in Australia and soon to be available in the Z4 Roadster). This in itself is quite outstanding for a normally aspirated engine.
Compared with the proven 3.0-litre normally aspirated magnesium-aluminium engine, the all-aluminium engine featuring new biturbo technol¬ogy increases overall output by approximately 15 percent. Peak torque shoots up by an even more impressive 30 percent. The resulting 225 kW and 400 Nm of torque deliver outstanding thrust and driving power all the way across the rev range.
The only way to achieve such an increase in power and performance with a normally-aspirated engine would be to significantly increase engine size, which would also mean a corresponding increase in weight and the negative effects on the car’s overall balance.
The BMW combination of turbocharger technology with high-precision petrol injection is a particularly efficient way to meet even greater demands in terms of output and torque.
And for comparison, the new straight-six biturbo weighs about 70 kg less than an approximately equally powerful eight-cylinder normally-aspirated engine displacing 4.0 litres. That is about the same weight as a moderately sized passenger.
Direct petrol injection also offers a significant fuel consumption saving of about 10 per cent compared with a similarly powerful turbocharged engine that uses regular fuel injection.
Turbines made of high heat-resistant special steel can withstand tem¬peratures of up to 1,050 °C and therefore do not need the cooling effect of extra air flow. Particularly under full load, this means a significant decrease in fuel consumption. High-precision fuel injection allows an even more exact dosage of fuel as well as a high¬er compression ratio – ideal conditions for increasing engine effici¬ency and significantly reducing fuel consumption.
All this is made possible by the central position of the piezo-injector between the valves. Fitted in this position, the innovative injector opening to the outside is able to distribute fuel in a conical burst en¬suring particularly smooth distribution of fuel within the combustion chamber.
Apart from its low weight and class-leading fuel economy, the new biturbo engine is able to offer yet another unique BMW feature. This is supreme smoothness and refinement, precisely the virtue which has made BMW straight-six power units the benchmark for refined drive technology, acknowledged the world over.
Indeed, the natural perfection of the straight-six layout gives the engine perfect balance in terms of free mass forces, avoiding vibrations even at high engine speeds.
A further important point is that this turbocharged version of BMW’s six-cylinder comes with the same hollow, extra-light camshafts as on the normally-aspirated engine, as well as an electrically driven coolant pump operating only as required.
The history of the turbo
Developing this new straight-six with biturbo technology, BMW is opening up a new chapter in the long history of the turbocharged engine, which dates back to 1905 and the work of Swiss engineer Alfred Büchi.
Initially turbo-charged engines were restricted to marine and aircraft engines. It was only much later that the technology migrated to cars.
BMW began its association with turbocharged road cars with the now famous 1973 BMW 2002 Turbo road car.
During the late 1960s, BMW was the first manufacturer to use turbocharged engines in touring car racing.
And in 1983 a BMW Brabham driven by Brazilian racing driver Nelson Piquet became the first turbocharged F1 car to win the Formula 1 World Championship.
Even back then, BMW’s engine specialists were able to extract far more than 1,000 horsepower from an engine displacing just 1.5 litres.
Now BMW is ready to open a new chapter in turbo-charged petrol-engined road cars and reset the bench-mark for dynamic driving with forced-induction.
Over and above the drivetrain conceived and built for supreme dynamics, this technology provides the starting point for a lean-burn direct injection concept and thus serves to successfully optimise fuel consumption also in other performance classes.
In this way BMW is once again proving its competence in engine construction, developing modern drive concepts and at the same time enhancing that sheer driving pleasure of BMW to an even higher standard.