What a bunch of hokey. I'm familiar with the perfect balance of an I6 vs. the imbalance of a 90-degree V6. That's the theory. In practice it's impossible to claim one of these engines is smoother than the other. Seat of the pants at idle, moderate acceleration, full throttle - there's no difference. Both are impressive in their control of NVH. I'll grant the sound of an m104 - or any inline six - is more soulful than the generic mooing of a V6.

In practice I like the m112 in my 210 car quite a bit better than the m104 in my 124 car. The m112 has wonderful midrange torque that pulls the car smartly along without working hard. In contrast, the m104 has to be revved hard to get anywhere. And the workings of its various manifold flaps (for Helmholtz tuning) and intake cam advance/retard mechanism are clearly perceived as slight hesitations and surges in acceleration. I find it quite annoying actually.

The three valve design of the m112 (and m113) engines was largely driven by emissions. The single exhaust valve retains more heat in the exhaust gasses and brings the catalyst online sooner. That's why these cars qualify for ULEV status - they are very clean running.

As for why BMW uses only inline sixes? I think there are two fairly obvious reasons. Primarily because it is their trademark, so to speak. A BMW isn't a BMW unless it has a straight six - the two are inseparable. A second reason is likely financial. BMW is not a particularly large automobile company. In fact, they are one of the smallest remaining independent manufacturers in the world. Developing a completely new engine line is a hugely expensive proposition - one that would strain their finances. So they soldier on with the inline six, turning what most companies would perceive as a liability into an asset. With BMW the engineering is solid, but it's the marketing that really impresses me.

- JimY