BMW will continue to keep the pressure on its rivals this year, thanks to an announcement that the automaker will launch a new high-performance, high-efficiency turbocharged I4 engine for use in its U.S. lineup. The new mill leverages BMW’s latest powertrain technologies to deliver both more power than the automaker’s normally aspirated I6 engine, but without sacrificing fuel economy.
Just as importantly, that extra power is more usable, too, since it’s available at much lower revs than with the I6. The I4’s 240 hp maximum is reached at 5,000 rpm—1,500 fewer than in the six-cylinder engine—and the 260 lb.-ft. of peak torque comes on at just 1,250 rpm—also 1,500 fewer than in the bigger engine.
Keys to this kind of performance include three notable BMW advances. First, the I4 boasts BMW’s High Precision Injection direct-injection system, capable of injecting fuel at up to 2,900 psi. In addition, because the system is configured so that the fuel is injected in very close proximity to the spark plug, combustion is cleaner and more homogenous.
Drivers also will benefit from the automaker’s patented VALVETRONIC variable-intake valve-lift control system. With VALVETRONIC, the typical throttle-valve system used in conventional engines is eliminated and the combustion air mass is controlled inside the engine itself. The results: A faster response, fewer pumping losses and increased efficiency.
The engine features twin-scroll turbocharging as well, making for a further advantage. With this system, exhaust gases from the engine’s cylinders travel along two separate, spiral paths as they flow through the exhaust manifold and turbocharger. This keeps exhaust back-pressure low at low engine rpm, helps optimally manage exhaust-gas energy and eliminates throttle-response delays.
BMW will release information about which vehicles will get this powerplant in the near future, but has confirmed it will come to the U.S. later in 2011.
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