Renault F1 Finding added horsepower despite freeze
Given the current engine freeze enshrined in the regulations, it is still possible to find a few extra horsepower by optimizing combustion and limiting friction as the Renault F1 team explains….
Fuels - a limited framework
The Formula 1 technical regulations are very strict. For several years now the fuel formula has been confined within a very precise framework by limiting the amount of hydrocarbons in the composition of the final product. Today, an F1 car has to run on lead-free petrol, which must meet draconian pollution restrictions. Furthermore, 5% bio fuel will be added to the mixture in 2008. There is still a tiny window for maneuver, though, and this is what interests the petrol companies.
The combustion process must be increasingly rapid to release the power. The petrol has to vaporize very quickly in a homogeneous fashion, and the flame spread has to be almost instantaneous. The aerodynamics of the combustion chamber, the flow from the injectors, the design of the plugs and the electronics all play their part. It is the same thing for the quality of the fuel, which is formulated on a bespoke basis for each engine.
This being said combustion is not everything. Today, the idea of consumption and the density of the fuel have an important role to play. By varying the energy in a specific dose of fuel it is possible to modify race strategy. So the top grade unleaded that the RS27 V8 burns has a density close to 725kg/m3 as compared to 750kg/m3 for the fuel from a pump. The aim is to be lighter while maintaining the same performance. The final result is a specially formulated fuel made up of 200 ingredients that enable the team to gain some extra horsepower. So the V8 Renault uses unleaded premium 95 octane fuel. If it used the same fuel as a Clio it would suffer a power loss of around 5%, some 35 bhp!
Lubricants: freedom to innovate
In the face of the freeze imposed on the V8 engines by the technical regulations, the engineers try to optimize the energy unleashed during combustion by limiting internal engine friction. In this area the viscosity of the lubricants plays a decisive role. It conditions the performance of the running gear: crankshaft, con rods and pistons. The film of oil between the metal parts must be thin enough to ensure maximum slip speed.
These components and the oil have to cope with enormous physical constraints. A piston, for example, goes from 0 to 37 m/s almost 600 times per second. If some parts of the engine like the middle of the ring of the piston’s skirt or the bearings – outside their critical cycle – have an oil film whose thickness is relatively satisfactory (2 to 3 microns), there are others, like the distribution, for example, that are separated by a few thousands of microns. But this race for power must not compromise reliability.
In the area of the distribution the pressures generated are in the realm of a Gig Pascal (100 tons/m2) under which the oil solidifies! The lubricant is heated and splits, and the film can disintegrate. High-pressure contact between metallic parts leads to a loss of power and the risk of engine failure. So it is necessary to have the right formula to protect the engine from wear, not too thin but not too thick either. It is also possible to work on the additives to create an additional film that protects the surfaces.
Hand in hand
The technical partnership between Renault and Elf is an ideal one as it is based on shared values, transparency, progress through innovation, links forged over a long period etc. The quality of communication can also make the difference. Special attention is paid to three areas in particular when formulating a lubricant: the distribution (especially the pressure on the camshafts) the pistons and the bearings.
What’s more, the operating temperatures are higher from one year to the next as the aerodynamicists are always looking for ways of making the bodywork more compact. Each of these areas requires a specific response in terms of viscosity and anti-wear properties. Where the fuel is concerned the aim is to speed up the combustion process even further.
A V8 engine is used more at the upper end of its rev band than a V10. New fuels and lubricants were homologated specially for this engine. They then underwent several evolutions to increase the V8’s power output. The aim for 2008 is to continue along the same path. Renault