XSeries-forum

Just got to say my x has gone in for a few warranty jobs and they've load me a new 320d gt and i have to sa its shocked me, the little 20d twin turbo engine is a cracker! no matter what i do i cant get under 40 mpg, its feels very nippy / quick for overtakes etc, in all fairness the car does everything very well just a shame the looks are slightly, well challenging.....but it drives nice, spacious (very compared to the e91) and overall just a good all round car.

Having the 520d that I believe is a single turbo I know what you mean, does a very good job in most if not all day to day tasks.  Not driven that hard but still impressed with an average of 50 mpg.  I don't think the 3 Series GT is too bad to look at, the 5 Series GT certainly seems more of a Marmite car.

Don

It's definitely twin as it says bmw twin power turbo under the bonnet

Single turbo which is twin scroll

what ever it is it went like stink for what it was, is it just a marketing ploy then with the twin power turbo a=on the engine

A twin scroll is a single device split in two just running on a common shaft.  It's done by splitting either or both the turbine and compressor 'wheels' into pairs so each is either fed by, or feeds, half of the cylinders.  Supposed to be a much smoother system as it avoids odd pressure waves that all cylinders might produce due to valve timings.

It's a cheaper engine to produce on the whole. However, and this won't apply to many, the n55 which is twin scroll is far less tuneable than the full twin turbo n54 engine it replaced.