While BMW is pushing toward the electrification of its vehicles in the long term, it still sees great potential for conventional engines. The company says, therefore, that in the medium term, the internal combustion engine will remain the BMW Group’s underlying technology and will thus power both existing and future series of volume production vehicles as the standard drive unit.
At the BMW Group Innovation Day 2012: Efficient Dynamics, BMW introduced a completely new engine family—gasoline and diesel—to take advantage more effectively of its current TwinPower Turbo technology and to create what it called an “unprecedented” degree of commonality across the platforms. The first member of this new generation of internal combustion engines will be an advanced three-cylinder TwinPower Turbo gasoline unit—an example of which is being applied in the Concept Advanced Tourer plug-in hybrid to be shown in Paris. (Earlier post.)
Building blocks. Building blocks for the new engine family include the TwinPower Turbo technology and VALVETRONIC.
BMW TwinPower Turbo technology, which today is already fitted to many gasoline and diesel engines and which will eventually be available for all new engines, is a core technology in the on-going endeavor to reduce both consumption and emissions.
The term “TwinPower” designates the combination of variable load control on the one hand and the latest fuel injection technology on the other. The intelligent, regulating technology modules include the (double) Vanos infinitely variable camshaft control system, the VALVETRONIC variable valve timing system and the variable turbine geometry of the diesel turbochargers.
These are complemented by the High Precision Injection direct fuel injection system for gasoline engines and the Common Rail direct injection system for diesel units. The third element of this high technology concept consists of turbo-charging.
This allows a BMW TwinPower Turbo engine to be charged with a single turbocharger, dual turbochargers, a twin scroll turbocharger or with a triple turbo unit. An essential feature of these engines however, is the VALVETRONICthrottle-free load control system. Unlike a conventional load control system using a throttle valve, VALVETRONIC responds to the driver’s power requirement by varying the valve lift, which results in systemic efficiency gains.
VALVETRONIC, the variable valve control system, is a technology for the throttle-free load control of gasoline engines, which the BMW Group has deployed since 2001.
The latest generation of the VALVETRONIC system employs a high-precision mechanism with an eccentric shaft to vary the valve lift on the intake side. Since the change in valve lift is infinitely variable, the usual throttle valve can be dispensed with during normal operation of the engine. Because the regulation of the required air mass takes place within the engine itself, the throttle losses in the charge cycle and thus the consumption can be reduced to a minimum.
The engine is now more responsive, since in contrast to engines with conventional load control, throttle-free operation ensures that ambient pressure is nearly always present at the intake valves and thus the time necessary for filling the intake manifold with fresh air is eliminated when the driver needs more power quickly.
The VALVETRONIC system delivers gains in efficiency—including improved engine response and better engine torque development—over the entire rpm range of the engine. The throttle-free load control system works like a dimmer, affecting all cylinders equally; the engine continues to run smoothly and its acoustic properties remain unchanged, something which cannot be said of cylinder deactivation, BMW notes.
“Dimming instead of switching off” results in minimum fuel consumption and emission levels, while maximum dynamics, matchless comfort and sophisticated power delivery are achieved, BMW contends. In addition, this proprietary BMW technology can be used in engines of different sizes and power.
The 1.5 liter BMW TwinPower Turbo power unit. Since BMW TwinPower Turbo technology can be integrated into engines of all capacities and any number of cylinders, it is suited for the future Efficient Dynamics family of engines. One of the first members is a 1.5-liter, 3-cylinder in-line BMW TwinPower Turbo engine.
The 1.5-liter BMW TwinPower Turbo engine features significantly reduced fuel consumption by virtue of its low internal friction. Due to the long ignition intervals, the charge cycle can be particularly well adapted to suit the needs of the driver, providing a high “low end torque”, as well as a rapid response. To this end, the new three-cylinder uses the latest generation of the High Precision Injection direct fuel injection system and the VALVETRONIC variable valve control system.
In terms of vibration characteristics, the three-cylinder engine shares a number of common features with the six-cylinder in-line engines—neither of them generates free inertial forces nor free moments of inertia. The three-cylinder engine is also free of first and second order inertial forces and the roll torque, which is very small compared to the six-cylinder engine, is completely eliminated by the use of a balance shaft. With its torsional vibration damper, which works on the principle of a centrifugal pendulum, the engine behaves well even at low rpm, providing a comfortable ride.
Because the frequency of the sound of a three-cylinder engine increases 50% faster than that of a four-cylinder, the engine is perceived as being extremely vivacious and sporty.
The new engine family. Currently, BMW applies TwinPower Turbo technology in gasoline and diesel engines of various powers and capacities. With the introduction of the new Efficient Dynamics family of engines, this technology becomes the common characteristic of both types of engine, with three, four and six cylinders.
Through the targeted development of additional components that can be used both for gasoline and for diesel units, the BMW Group is increasing the number of identical components within the family even further. In this way technical solutions in both current and future versions can be used on all of the engines, regardless of the number of cylinders, combustion method and power.
Common design principle and modules. The basis of the new family of engines is a common design principle for in-line units. The basic engine is made up of optimized cylinder modules with capacities of 500 cc each, developed to optimized thermodynamic efficiency for use in a passenger vehicle. Consequently the new three-cylinder engine has a capacity of 1.5 liters, the four-cylinder unit is 2.0 liters and the six-cylinder is 3.0 liters. The power developed in each cylinder is between 30 and 55 kW (40 and 74 hp) with 60 - 80 N·m in the case of the gasoline engine, while the diesel develops between 20 and 45 kW (26 and 60 hp) with 75 - 110 N·m.
The structural similarities between the gasoline and diesel engines include the distance between cylinders, the aluminium crankcase, the balance shaft design, the arrangement of the timing chain, the layout of the cylinder head bolts and the high-quality coating on the cylinder bore surfaces.
Overall, the number of identical parts used in engines powered by the same type of fuel climbs to 60%, while the level of structural similarities between gasoline and diesel engines is around 40%.
Even more benefits are provided by standardized interfaces. In addition to the identical engine mounting points, these are primarily the interfaces to the cooling circuit, the intake and exhaust manifolds and the heating and air conditioning systems. Compared to current models, the number of possible combinations in these areas has decreased by about half.
Finally, all of the power units have the same “cold” intake and “hot” exhaust sides. This is why the three and four-cylinder engines in this new family are suited to both longitudinal and transverse mounting in future BMW and MINI models.
With the new modular engine, the BMW Group will in future be able to build three-, four- and six-cylinder power units delivering different levels of performance, each matched to its respective vehicle. This results in larger volumes, leading to significant savings in both development and production. In addition, the high degree of commonality facilitates the development of additional engine versions, which can then be realized economically at short notice, even in relatively small numbers, according to the company.
For the first time, gasoline and diesel engines belonging to this new range can be manufactured together, at the same time, in the BMW Group’s engine production facilities. In this way, even short-term fluctuations in demand or new market developments can be addressed flexibly.
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