google translate from Italian Magazine - 2016 Mercedes Engine
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POWER UNIT: MERCEDES CONTINUES AGING DELL'HCCI PLUS
Even for beginners it is very clear that the history of engines speaks primarily of two distinct functions:
ignition (classic Otto engines or improperly called a "petrol")
ignition (classic diesel engines)
From a theoretical point of view, the diesel engines have the highest efficiency values ​​of spark ignition engines, besides not being characterized by heavy penalties in terms of efficiency at partial loads typical of spark ignition engines. But usually on sports cars they are installed ignition engines, petrol engines.
Mercedes from the first half of the 2000s has invested a lot of money to try to "put together" the positive characteristics of the two types of engines by eliminating this union the negative characteristics; to do whatever they have developed different concepts of combustion, in particular the solution called HCCI (Homogenous Charge Compression Ignition) or better known as DiesOtto. And it is an evolution of the technology that is making a difference in the power unit German.
Briefly, how does this "new" type "(HCCI base) engine? When the engine has to deliver full load behaves just like a normal petrol, with the spark that triggers the combustion of the air-fuel mixture and combustion" homogeneous ". But when the engine will run at partial loads, combustion occurs spontaneously by increasing the compression ratio as a simple diesel engine, which as we have said before has a better efficiency.
The secret is in being able to raise the bar of the intervention that is controlled by the ignition when the engine switches to operate as a "classic petrol". Mercedes honing month after month this stage, continues to find CV and to get especially specific consumption always lower, fundamental in modern Formula 1.
In the HCCI technology is going to generate a homogeneous mixture between fuel and air, similarly to what occurs in the spark-ignition engines, having, however, the combustion through compression of the same, as in compression ignition engines. The advantages which are they? What are interested in doing so the combustion mixture in its entirety without developed through a propagation of the flame front is typical of spark-ignition engines and without phenomena only diffusive typical of compression ignition engines.
But there are also problems; one of the main is in the pressure peaks (especially on the cylinders) and mechanical stresses that the mixture generates, usually not viable for the motor above the low to medium loads. And here is the continued evolution of Mercedes: already in 2015 there have been improvements in technology, though problems still had to cylinders have especially on Force India and the two Mercedes official as to require major changes to the internal combustion engine reliability has been introduced in Canada on the cars of Hamilton and Rosberg. Another step, fundamental to what we were told was made ​​with the engine introduced by Mercedes at Monza, where the famous rod of which we spoke just above, has been significantly raised but with all the problems that may ensue.
In addition to problems related to stress, the HCCI engines are characterized by a difficulty in controlling the combustion, a factor that makes it difficult for proper management of the engine are very irritating especially vibrations (remember what I said that caused problems on the first PU Mercedes Championship races in 2015?) that are generated and that resulted in some problems to the power unit of Germany, as well as in the first part of the championship even then in Monza and Singapore. And here is behind the great work he is doing in the Italian headquarters of Petronas Turin preparing synthetic fuels suitable for this type of engine. Without the fundamental contribution of Petronas, this type "innovative" engine could not function like it is working on spaceships Hamilton and Rosberg.
It is thanks to this technology that Mercedes boasts a return on its combustion engine very close to 50%, a value that when compared to common car seems almost science fiction.
The new power unit that will debut in Barcelona, ​​was made interventions aimed at solving the above problems encountered in the season finale but without forgetting the performance side of the drive unit (thanks to some new components with higher efficiencies) that will gain even horses.