BUDAPEST, Hungary — Mercedes has put a fix in place for the engine issue that was limiting George Russell’s top speed after uncovering its cause ahead of this weekend’s Hungarian Grand Prix.Russell, 28, revealed at last week’s Belgian Grand Prix that he was struggling with a problem on his engine which meant he was unable to reach the same top speed as Kimi Antonelli, his teammate and title rival, at certain parts of the circuit.Although the problem was initially thought to relate to his driving style and using too much battery power, Russell said at Spa that it was in fact a “serious issue at play”.His frustrations were not eased by his first-lap retirement in Sunday’s race after being spun by Lewis Hamilton, with Russell complaining angrily on the radio about a lack of battery power that led to him being swallowed up by passing cars at the end of a long straight.Speaking to reporters on Thursday ahead of this weekend’s Hungarian Grand Prix, Russell said that Mercedes was able to uncover the problem with his engine after Spa, relating to the software, and has now put a fix in place.“Effectively, it was numbers on the screen that were not quite calibrated properly,” Russell said. “So it’s not like the hardware is wrong or there’s a problem with the hardware.”Russell explained that he’d struggled with his battery deploying energy at the most optimal points of the lap at Spa — the longest track of the year where engine performance is critical — but there was also a separate issue that was linked to the software calibration.“I’m not going to say simply numbers on the screen,” Russell said. “But now we know which numbers potentially were not correct. We can rectify that, recalibrate things, and get the (engine) performing at its full potential.”Russell added that Mercedes was “pretty confident” the software problem had now been fixed.In Spa qualifying, Russell finished more than half a second behind Antonelli, who took his sixth pole position of the year. Antonelli was as much as 5.6mph faster than Russell at points in the final sector, which was a long, flat-out section.Russell said there’d been times where he’d also struggled with the engine problem through the British Grand Prix weekend at Silverstone, only for the issue to be worse at Spa.“But for me, this is now history,” Russell said. “It’s behind me now. I’m just looking forward to Budapest. It’s a circuit I like. It’s going to be a really challenging weekend.”Russell was the preseason favorite for the F1 world championship, having led Mercedes’ efforts through much of his previous four seasons with the team. He comfortably won the opening race of the year in Australia from pole position.But 19-year-old Antonelli then seized control of the title race by winning five straight races. His victory in Belgium, combined with Russell’s retirement, left a 50-point gap between them at the top of the standings coming into the Hungary weekend.Russell admitted it was “a huge load off my mind” to know the problem was nothing to do with his driving style, with the practice sessions spent at Spa trying to adjust his approach being “kind of for nothing” in the end.“I’m looking forward now just going into a weekend where I can just try and focus on driving fast, focus on the simple things,” Russell said. “I know that is when I perform at my best, but we’re not in a simplistic sport.“So saying let’s just solely focus on the simple things is easier said than done sometimes.”