Just before BMW updated the G30 5 Series range for the 2021 model year, the N63 V8 in the M550i xDrive was updated from the 456-horsepower N63B44O2 (N63TU2), to the 523-horsepower N63B44T3 (N63TU3), for the 2020 model year. In addition to the horsepower bump, and specific changes which you can read more about in our examination of the N63 and S63 V8 engines, torque is also increased from 479 pound-feet from 1,500 to 4,750 rpm to 553 pound-feet from 1,800 to 4,600. That’s the same amount of torque as the latest version of the S63 M V8, and exactly the type of gain which should translate to improved acceleration for a vehicle with standard all-wheel-drive.
During Car and Driver‘s testing of the G30 M550i LCI though, the numbers didn’t add up. BMW’s zero-to-60 claim for the model is 3.6 seconds, an improvement of 0.3 seconds over the 456-horsepower pre-LCI version’s 3.9-second time. When tested back in 2017, Car and Driver recorded a zero-to-60 acceleration time of 3.8 seconds for the 2018 M550i, but when the magazine tested a 2021 model year example with the 523-horsepower engine, the best acceleration time the car could manage was 4.1 seconds. The results were perplexing enough that Car and Driver requested another M550i from the press fleet, but the lowest number that car could manage was 3.9 seconds.
Still unsatisfied with the results, Car and Driver asked for yet another M550i, this time from BMW’s West Coast press fleet, a request that was denied when the magazine was informed that BMW had located a fault that wasn’t exclusive to the cars the magazine had already tested. This week, Car and Driver reported that BMW has discovered that the 2021 M550i suffers from a problem related to communication between the engine and the stability control module which results in a drop in turbocharger boost pressure. The problem is also said to affect all 2021 540i xDrive models, which use the B58 six-cylinder engine, but have the commonality of xDrive.
To remedy the fault, BMW will be issuing an over-the-air update this summer for the affected models. Car and Driver says it intends to test a patched M550i as soon as one becomes available, and we look forward to seeing, analyzing, and reporting on the results.—Alex Tock
[Photos courtesy BMW AG.]