Clever Audi concept uses a second, electrically-driven compressor to quicken spool.
http://www.automobilesreview.com/auto-news/audis-electric-bi-turbo-engine/54084/
Supposedly good for 313 HP and 480 lb-ft at just 1450 rpm... and gets 36.75 mpg... :drool:
Needless to say, money saved on fuel...