In June of this year, we reported on the recently updated M550i xDrive underperforming expectations when Car and Driver put it through their test protocol. Although BMW claimed a zero-to-60 acceleration time of 3.6 seconds for the nearly 4,500-pound sedan, press cars tested by the magazine could only manage as low as 3.9 seconds. Acceleration isn’t everything, but that number put the 523-horsepower M550i xDrive LCI behind its 456-horsepower pre-facelift predecessor, and even with the significantly heavier X5 M50i, both of which the experts at the magazine also tested.
BMW learned of the problem, and the company’s engineers quickly assigned blame to a fault in communication between the engine and the stability control module on not only the M550i xDrive, but also the B58-powered 540i xDrive. The problem translated to the engines being limited in their ability to develop full power thanks a drop in turbocharger boost pressure, ultimately resulting in slower off-the-line acceleration.
The promised fix has now arrived, per the magazine, and is available either as an over-the-air update, or as something your local dealer can be tasked with. When Car and Driver tested an updated 2021 M550i xDrive, the evaluation proved to be the final one needed for the M550i xDrive LCI to prove itself. The zero-to-60 acceleration time dropped to 3.5 seconds, and the quarter-mile comes and goes in 11.8 seconds at 119 mph.
The M550i xDrive indeed remains a value proposition in the lineup when compared with the M5 Competition, and it’s also probably the one you’d rather be driving on a daily basis.—Alex Tock
[Photos courtesy BMW AG.]