Over a week ago rumors began to sprout of a 3-series four-cylinder making it to American shores. No confirmation, either positive or negative, has been forthcoming from the company, and the same can be said of the four-cylinder turbo. No models have been mentioned as potential recipients of the turbo-four, but the 3-series, 1-series and Z-cars are likely candidates, from a purely logical point of view.
Speaking with MotorAuthority, however, Tom Plucinsky, BMW's North American product and technology communications manager, said that the question lies heavily in how the EPA will deal with California's request to legislate its own emissions standards. Because the states CARB emissions standards are used by about 10 other states, the impact on BMW's - and the industry's - sales could be significant, and could create a legitimate business case for the introduction of a twin-turbo four-cylinder.
That decision will essentially be made by the next administration, as the EPA is an Executive Branch administrative agency. The current EPA decision is that state-by-state emissions decisions do not fit within a national framework, but that could easily be reversed in future. Part of the challenge facing the industry should the EPA allow California to regulate its own CO2 levels is that such a rule is effectively a back-door into fuel economy regulations. The amount of CO2 emitted by an engine is directly related to the amount of fuel it burns, so it's essentially a different way of stating the same requirement.
And in order to meet that requirement, cutting back on the displacement and number of moving parts in the engine is likely to become necessary. It won't be a cheap decision, however, as any BMW four-cylinder would still have to feature advanced technologies like direct injection and twin turbocharging to ensure the high level of performance and efficiency called for by the application. Those technologies are currently found throughout BMW's lineup in one form or another, especially its inline-six-cylinder engine range, and they can be expensive to employ.
That means that while a twin-turbo four-pot can provide greater cruising efficiency with about the same maximal output as a six-cylinder, it won't necessarily be any cheaper to produce or purchase.
Nevertheless, BMW feels its American customer base is prepared to accept the idea of a high-performance four-cylinder, and is keeping the idea in the mix. Also on the table for future solutions to efficiency and emissions issues are hybrid, hydrogen and even diesel fuels, though hydrogen and hybrid solutions will likely remain on the horizon for some time. The twin-turbo four-cylinder could be seen as a sort of interim solution since BMW already has a strong selection of four-cylinder engines outside the U.S., plus all the technology and equipment necessary to build a high-performance forced-induction version should a viable business case arise.