BMW has only "two engines", one with 4 and one with 6 cylinders. They have a base cylinder with 0.5 liters, and build engines with multiple of those. Ergo why they announced the 1.5l 3 cylinders for the upcoming generation.

The detuning is mostly for countries where the tax is based on the engine power. For example, the 116/316 and 118/318 models in some countries still have the 2.0l engine (albeit usually the previous generation)

Then on the other side of the scale, the 23 and 35 are still the 2.0 and 3.0 liter engines respectively, but both with the bi-turbo technology.

__________________
My BMW: Photos