Engine development

The good news is that Andy Cowell at Mercedes told me that with the 25 'tokens' available to upgrade engines over next winter he could almost start again. And so if Renault and Honda know what to do, they can play catch-up. However, that message also demonstrates that Mercedes won't be standing still.

SkyF1  The performance of the upgraded Mercedes engine that powered Lewis Hamilton to victory in the Italian Grand Prix has underlined the incredible pace of engine development in the hybrid era.

The full potential of what is essentially the prototype for Mercedes' 2016 engine was only really hinted at in the first practice session of Friday morning when they were being run in aggressive trim in an attempt at quickly highlighting any potential problems.

Thereafter, the units were turned down in the interests of reliability – and the engine in the back of Nico Rosberg's car had to be removed and replaced by an old standard-spec unit after suffering a leak in Saturday morning practice. But in P1 on Friday their end-of-straight speeds, combined with information gained by other teams via GPS-tracking suggested the new motor could have been as much as 40bhp more powerful than that which was already dominating the season.

It would be more accurate to say that the combined power unit and Petronas fuel was more powerful – for fuel technology has proven to be the most potent development tool in the hybrid turbo-charged formula since its introduction last year. It's a similar story at Ferrari, where gains of 40bhp have been made during this season, just from the fuel alone.

The heart of the Mercedes upgrade was a new fuel composition from Petronas that allowed a change in the combustion chamber shape of the engine. The fuel alone would not have made anything like as much difference with the old engine. Likewise, the new engine would not be as powerful as it is if the old fuel was used. It's a symbiotic process of development – "lots of small steps together that make one significant step in total," as Mercedes HPP boss Andy Cowell explained. "It all comes together beautifully."

What the fuel and new combustion chamber shape combined allow is not just a bigger explosion in the combustion chamber – but a flame of greater duration, enabling the parts to be exposed to it for longer and thereby making the ignition less critical. This makes the engine more resistant to detonation – which is the chief limitation to power with this type of engine. Detonation is the phenomenon whereby the ignition becomes uncontrolled and uncoordinated with the delivery of the fuel mixture into the combustion chamber.

If it spontaneously ignites at the wrong time it can prove disastrous for the engine. The more prone the engine is to this uncontrolled ignition, the more conservatively its settings have to be to avoid it – and the less power it makes. Delay the onset of detonation with a new fuel composition and/or a better combustion chamber design and the engine can be run more aggressively, giving more power for the same fuel consumption or better fuel consumption for the same power.

This resistance to detonation is believed to be the biggest single advantage enjoyed by Mercedes over the rival Ferrari and, particularly, Renault, which is believed to be poor in this regard. This advantage compounds in the hybrid era, for the more power that is produced, the more heat that is created for the ersH to recover, giving greater electrical power too.

The necessity for the engine and fuel to be developed together in this formula was underlined last year when McLaren ran Mercedes engines as customers but was contracted to run Mobil fuel. Despite identical engines to the works cars, the McLarens were often as much as 40 horsepower down.