Software glitches can cause annoying things.
The BMW M550i xDrive, which received a refresh last year, is more than good enough for a majority of performance sedan customers. If not, there's the M5. The former comes powered by a 4.4-liter twin-turbo V8 packing 523 horsepower and 553 lb-ft of torque. Like we said, more than good enough.
But Car and Driver noticed something when they tested the sedan a few months ago. Its 0 to 60 mph time of 4.1 seconds, while not exactly slow, is still 0.2 seconds slower than the X5 M50i, which shares a powertrain and weighs 856 pounds more. What gives? The first step to correct the issue was to refill the sedan's tank with high octane 93 fuel.
That dropped the sprint time to 3.9 seconds, though BMW claimed a 3.6-second time was possible. Oftentimes, it's possible to improve automaker's performance claims; BMW is known to take a conservative approach in the matter. Not being able to achieve a sub-3.9-second time didn't go unnoticed by BMW and it quickly put its engineers to work. Something just wasn't quite right. And, lo and behold, there was a problem. A previously unknown software glitch was uncovered that caused a miscommunication between the engine computer and the stability-control module. The stability control was intervening during a standing-start launch, instructing the engine to reduce boost.
This resulted in not being able to achieve the full 523 hp, thus adding a few tenths of a second to 60 mph. Not only did this affect the M550i but also the 540i xDrive. BMW has updated owners there's now an over-the-air update fix available. Alternatively, a dealership technician can handle the task. The car's newly tested 0 to 60 time is now 3.5 seconds, while the quarter-mile happens in 11.8 seconds at 119 mph. All's well that ends well.
Not every automaker pays this close attention to tiny details like this, but this is the ultimate driving machine we're talking about. Details matter.