[sparoz]

I think most people are missing the point. Firstly, in terms of N54 technical advance, it is not as good as the N52. One of why I and many people who love the NA engines are because of Valtronic which is not present in the N54.

BMW now can use Valtronic on the N55 engine, at the same time, it changes from a twinturbo setup to a twinscroll setup, which basically does the same thing - the twinscroll basically have two fans on the same housing where the smaller fan spool up first and than the larger (lots of information on the net). The fact that the N54 has two turbos doesn't mean it is better.

As someone mentioned before, the N55 would probably mated with the new 8 speed gearbox, which will possibly even make it faster. So, I do believe it would be an upgrade.

As far as the IS is concerned, it only make sense they have now tested the drive train with the updated 245kw N54, with DCT that they would stick with those setup for the IS versions, where they are either, a) not have enough testing done on the capabilities of the N55, or b) reserved the N55 twin turbo for the M1, where it will have valtronic, a twin scroll for everyday driving, and a larger turbo for higher end torque.

I know I am a bit speculative, but really, I think the N55 would be more than worthy as the successor to the N54.

The only disappointment would be from dumbo's ears for the 2011, and definitely not the engine.