Think Germany's RB26DETT and 2JZ.
Nowadays turbochargers are pretty standard on cars. They come on just about every single type of engine configuration there is. It was revealed a long time ago that turbocharging is possibly the most efficient way to make power, and BMW was on the forefront of this development. In 1973 BMW was the first carmaker in Germany to release a production turbocharged car, the 2002 Turbo. It also basically defined what "sports sedan" means as we now know it.
BMW continued its turbocharged ascension to greatness in 1983 when it became the first turbocharged engine manufacturer to win the Formula 1 world championship with Brazilian Nelson Piquet at the helm. That year BMW was able to get more than 1,000 horsepower out of its 1.5-liter inline-four for qualifying sessions. Fast forward to 2006 and BMW again made a stamp in the history of turbocharging in the form of its N54. The N54 debuted in the 2007 model year 335i as a twin-turbo 3.0-liter inline-six, making 300 horsepower at the crank and almost 300 lb-ft of torque. While the 300 hp peaks at 5800 rpm, the torque stays constant at 295 lb-ft, from 1300 rpm all the way up to 5000 rpm.
This is possible in part through BMW's VANOS system. VANOS is variable camshaft control, and it allows the camshafts to move according to engine speed.
At low speeds the camshafts will move to open the valves later in order to make the engine smoother and improve idling. The N54 also uses direct injection, where highly pressurized fuel is sent directly to the cylinder's combustion chamber. The N54's cooling capabilities are also a big part of the engine's power, as its intercooler is designed to cool the turbocharged air by up to 80 degrees Celsius. Now the purpose of it having two turbochargers is to eliminate "turbo lag." At low engine speeds one turbo builds pressure while the other stays idle, so as to reduce the amount of time it takes for the turbo to act. Because the computer controls so much of the engine, a decent tune will get some good power gains out of the engine.
However, with some bolt-ons and a twin-scroll turbocharger, N54 owners are reporting power gains of up to about 707 horsepower at the wheels, without changing the internals. This is because from the factory the N54 came with forged internals. While which specific parts were forged and which were cast is up for debate, it's widely accepted that the crankshaft and rods were forged while the pistons were cast. Still, without changing internals that's an impressive power gain, from 300 to more than 700 whp. The N54 was put in the 335i until BMW made what's believed to be a more cost-effective engine, the N55. The N54 was used in the 335i from 2006 until 2010, the 135i from 2008-2013, and the 740i from 2008-2012.
A more powerful version of the N54 went into the Z4 sDrive35is. The N55 is thought by some to be a step down from the N54, though it makes the same, if not more, power as the stock N54, depending on the year. Its weak point could be its tuning capabilities, as it has cast internals and only one turbo. Could the N54 be the next 2JZ? Like the Toyota engine and Nissan's RB26DETT, the N54 has the ability to become legendary, especially among tuners. It must be a coincidence that all three are inline-six engines.