Mercedes identifies Russell's F1 power unit software issue

George Russell will have to wait until the Italian Grand Prix to find out whether Mercedes has truly identified the cause of the anomalies that hampered him between Silverstone and Spa, as the team identifies the source of his power unit issue within its software.

The British driver repeatedly complained about a lack of performance on the straights, a feeling that was also confirmed by telemetry comparisons with team-mate Kimi Antonelli's car. The team's initial investigations quickly ruled out both a loss of power from the power unit and any deficit in top speed.

From the outset, the situation appeared far from straightforward. In the first sector at Spa – the entire stretch from La Source to the braking zone for Les Combes – Russell’s sector times were in line with Antonelli's, something that would not be consistent with a simple power deficit.

Only after qualifying was the team able to narrow down the search, identifying the software as the likely source of the anomaly. However, Russell's race, which ended just a few corners after the start, did not provide an opportunity to verify whether that hypothesis was correct.

According to Autosport, the root cause was found deep within the power unit management software code. It was a subtle anomaly that required several days of analysis before engineers fully understood it. Essentially, the software was deploying electrical energy too early, using an excessive amount during the first part of the lap.

The result was an imbalance in energy distribution: whatever was gained early in the lap inevitably had to be paid back in the later sectors, when the driver expected to still have electrical power available. This was most clearly evident in the final sector at Spa.

George Russell, Mercedes

Photo by: John Thys / AFP via Getty Images

A software correction has already been implemented at Mercedes' Brixworth engine facility, but it still needs to be validated on track. Some within the team believe that a less significant part of the issue may also be related to Russell's driving style, which could have amplified the effects of the software anomaly.

As McLaren team boss Andrea Stella recently explained, the current Mercedes power units feature adaptive logic that gradually learns a driver's habits, adjusting energy management based on their driving style. In the presence of a software fault, this learning process could have further intensified the unwanted behaviour.

Mercedes nevertheless believes it has identified the primary cause of the problem and does not need to replace the power unit.

But the team won’t get a confirmation of the fix until the Italian GP at Monza because neither the Hungaroring nor the subsequent race at Zandvoort offer conditions similar enough to Silverstone and Spa to properly evaluate the system under the circumstances that exposed the issue.

For Russell, at least in the short term, there is one positive aspect: at the Hungaroring, straight-line power has a much smaller impact on overall performance, allowing him to approach the weekend without the constant concern that he is being disadvantaged.

"When that thought is constantly in the back of your mind, it becomes difficult to focus solely on putting together the best possible lap," a source close to the team explained.