Red Bull has issued a fresh challenge to the legality of Mercedes' 2021 Formula 1 engine.
Since Silverstone, there have been suspicions in the paddock - notably from Red Bull and Ferrari - about how Mercedes upped its mid-season engine performance amid the current homologation rules.
"Red Bull has sent a request to the FIA in order to discover the secret," reported Auto Motor und Sport correspondent Michael Schmidt.
Earlier, Red Bull-Honda looked to have the upper hand in terms of outright engine performance, but that trend was reversed more recently.
Red Bull and Ferrari reportedly suspect that, based on GPS data, there are questions about how the Mercedes unit delivers power out of slow corners in particular.
"According to them, the secret is in the intercooler," Schmidt explained, adding that it is about the temperature of the compressed air for a 20 horsepower gain.
"That's where most of the laptime is gained," he said. "The question is how far the air can be cooled and whether the sensor is mounted in a place where relevant values can be determined."
