Details of the FIA's plan to limit the use of engine modes have been revealed in a report by Germany's Auto Motor und Sport.

On Friday, the technical directive was issued to teams which confirmed the introduction of the changes from Monza, one week later than initially planned.

This is part of a new push by the governing body to better police the complex power unit regulations, amid suspicions manufacturers are finding clever ways to breach them undetected.

The main aim is to try and make teams use the same engine settings in both qualifying and the race, with Mercedes in particular known for their Q3 'party mode'.

Although commenting last weekend, McLaren boss Andreas Seidl admitted some confusion in how it would be managed.

“To be honest, we only have this information from that letter, which is a confidential letter, but it doesn’t go into the detail of what actually the FIA wants to achieve, so we need to wait for that,” he said.

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“As you know, nowadays with these complex power units, there’s a big priority of different settings existing for different modes on the combustion engine, for different modes of the hybrid system, the way you use the battery for reliability, for power, for attacking, defending and so on.

“And in the end, we need to wait for what change, if there’s a change, it is targeting."

Well, now AMuS has explained that teams will only be allowed to use a single mode for the majority of Saturday and Sunday, but exceptions have been put into place for slow laps such as in and out laps from the pits, the formation lap and laps under Virtual and full Safety Car.

In addition, the overtake button will remain but can only be used in the race, addressing one concern raised by Valtteri Bottas that everyone in one mode could make racing tougher.

Teams will also be able to change the modes they can from use race-to-race, while ERS settings can be updated upon informing the FIA but not reversed.

As for any impact this will have on the competitive order, however...

“I think whatever the rule changes are, I think that with the capacities and capabilities Mercedes is having, whatever the rules will be, I’m sure they will keep being the benchmark in this modern hybrid power unit era," Seidl concluded.