Buying a supercar often leaves wealthy patrons with a hole in their pocket. McLaren Group's investors can doubtless relate.

Nine-figure recapitalizations have been regular occurrences at the storied British racing brand in recent years, amid deep losses and operational woes. But things are finally looking up for its sportscar business, McLaren Automotive Ltd., which not only has a new wealthy benefactor but a plausible business plan -- albeit one that will demand plenty of patience and cash to execute.