BBC Sport's chief F1 writer Andrew Benson in Bahrain:
"Why is the Mercedes so fast? That's been the question on everyone's lips since the start of the season and my good friend and fellow journalist Mark Hughes has uncovered the answer in this month's Motor Sport magazine.
"It's to do with clever thinking on the engine. Mercedes have split the turbine and compressor - which are normally sited next to each other in turbo engines - so that the compressor is at the front of the engine and the turbine at the rear. This means that the airflow has much less far to travel from intake, through the compressor and into the cylinders.
"This not only increases power but also reduces dramatically the amount of piping required for the engine, giving a significant advantage both in total weight and weight distribution in the car.
"On top of this, the design reduces lag in the turbo to almost nothing so that less power is required from the motor-generator unit attached to the turbo to spool it up to minimise lag before the drivers go on the throttle, so more of that power can be used directly at the rear wheels.
"Ferrari had the same idea, and their compressor is also detached from the turbine, but it is only about a third or so across the 'v' of the engine, rather than right the way across. Perhaps Ferrari were worried about being able to control the vibrations in the shaft connecting the turbine and compressor if it was as long as the engine.
"The Mercedes customer teams have not been able to take as much of a benefit from this advance as the factory team because they did not know about it until quite late last year, so were unable to develop their cars around it."