Hungarian GP: Renault engineering preview

Renault's Pat Symonds, executive director of engineering, and Denis Chevrier, head of engine operations, give their view of the Hungarian Grand Prix Pat Symonds: "Hungary, along with Monaco, is generally recognised as one of the most difficult...

Renault's Pat Symonds, executive director of engineering, and Denis Chevrier, head of engine operations, give their view of the Hungarian Grand Prix

Pat Symonds:

"Hungary, along with Monaco, is generally recognised as one of the most difficult circuits to overtake on. History has shown this to be the case, but let's try and understand why it is so difficult to overtake on any circuit, and more specifically at the Hungaroring. Many people feel that because modern F1 cars are such sophisticated aerodynamic devices, and derive much of their performance from aerodynamics, overtaking will be difficult to achieve until there are limits in this area. Let's think about why aerodynamics make overtaking difficult."

"In simple terms, the aerodynamic forces on the car are designed to increase the load on the tyres and therefore give them more grip. In doing this, they create a large turbulent area behind the car called the 'wake'. This is an area of disturbed air that is no longer travelling the expected direction and one can easily see this when watching the cars running in the wet. The large rooster tails generated behind the cars are indicative of the wake area but in reality, as water is much heavier than air, the wake is vastly larger than is seen by this phenomenon."

"Approximately speaking, the length of the wake is proportional to the square of the car's speed, whereas the total magnitude of it is proportional to the drag of the car. At high downforce circuits such as the Hungaroring, the drag - approximately one third of the downforce - is of course also high and hence the magnitude of the wake is even greater. Of course, this wake also includes a small low pressure pocket which, when a car is close enough to the one in front, allows it to slipstream and gain straight-line speed."

"At the sort of maximum speed we see in Hungary, of just over 300 kph on the main straight, the length of this wake is approximately 150m, which is over 20% of the length of the straight. The wake from the leading car has two fundamental effects on the car following it. Firstly, as an aid to overtaking, it reduces the drag of the following car and at extremely small distances, when one car is tucked right behind the leading car, the drag reduction is very large, bringing a gain in straight-line speed. Unfortunately, when the following car is further back in the wake, its downforce is severely affected, not just in magnitude but also in its front-rear balance."

"For example, if two cars are travelling at around 200kph, when the following car is ten car lengths from the one in front, it will experience a downforce reduction of around 20% and the balance will shift about 4% to the rear. This alone makes it difficult for the driver of the following car, because not only does he lose grip but the car also understeers a lot. As it gets closer to the car in front, things get even worse."

"At three car lengths' distance, the following car may have lost one third of its downforce and be experiencing an aero balance shift of over 15%. This makes it virtually impossible for the following driver to stay close to the car in front through any reasonably quick corner leading onto a straight, and if he can't stay close on the corner leading to the straight, then it is very difficult to use any speed advantage for anything other than catching up, rather than actually overtaking."

"Of course, if the cars had extremely limited aerodynamics, then this wake would be very small, but will never be non-existent: any body moving through the air will always generate some wake, no matter how streamlined it is, and in other formulae, one can see even touring cars slip-streaming each other."

"There are other factors which will either directly or indirectly affect the likelihood of overtaking in an F1 race. Some of these are contradictory. For example, if we increased the grip of the car to the road, perhaps by having larger tyres, then teams would tend to reduce the downforce as the optimisation of the total package would move in this direction: corner speeds would be maintained, and thus it would be possible to increased top speed by removing downforce. This of course would reduce the wake, and may make overtaking easier."

"Conversely, it could be agreed that if we were able to reduce the grip in slower corners, by alterations to the tarmac, and yet keep grip high in faster corners by banking them, then some of these faster corners could be taken flat out which would have the effect of joining two straights and making the straights longer. Of course, this would be a radical proposal for the circuit owners and require much research to get the numbers right, but circuit design undoubtedly does affect overtaking, and the general premise of a slow corner followed by a long straight and another slow corner is conducive to overtaking by F1 cars, in their current configuration."

"Having said that, even this type of circuit configuration cannot be taken as a sure-fire guarantee of exciting racing. The 'new' Hockenheim uses such a layout and although we had a very exciting race there three weeks ago, if we look at previous years, we saw just three competitive overtaking manoeuvres all race in 2003, while in 2002 the only overtaking came about as a result of teams making incorrect tyre choices: Barrichello, for example, spent 47 laps (two race stints) stuck behind a competitor during this race."

"So, even this kind of 'formula' for circuit design can produce poor racing. Equally, if we consider the British Grand Prix in 2003, it produced a fantastic race with a great deal of overtaking on a circuit that does not follow what has become the accepted layout, whereas 2004 produced a much more "normal" race. Circuit design is important, but there is no single effective formula for entertaining racing."

"These facts may lead us to draw a more relevant conclusion. Essentially, if cars are of similar, consistent performance and leave the grid together, there is no real reason to believe they will ever overtake each other. Similarly, if their performance is vastly different, and they are pre-sorted by speed, then the leading, faster cars will simply pull away. If we believe overtaking is important, then what we need to do is devise a method whereby the cars will have different levels of performance, at different stages of the race."

"This sometimes occurs if people use different types of tyres, which have different performance profiles through a race. It has also been employed in some form with turbocharged engines, where a limited number of over-boosts are allowed in a race. But overall, it is this concept of a variable performance differential between the cars that is central to generating overtaking during a race."

Denis Chevrier:

"Historically, Hungary has been characterised by its sporting aspects rather than its technical demands. It is a circuit at which overtaking is notoriously difficult, and modifications to the layout last year have not significantly changed this situation. While not as important as in Monaco, pole position still represents a major advantage."

With a layout that includes 16 corners in just over four kilometres, this is a circuit where a low percentage of the lap (51%) is spent at full throttle, and where the maximum speed is also relatively low, at just over 300 kph."

"Five of these corners are taken at less than 100 kph, and just two see speeds of more than 200 kph. However, the other interesting factor is that unlike in Monaco, there are no what might be termed unusually slow corners, and the slowest turn is the first corner, taken at 90 kph."

"Consequently, the range of engine performance is not as wide as at some other circuits, and during the race weekend we concentrate on optimising acceleration between 90 kph and 250 kph. We have made significant progress with in-gear performance during the season, and this will allow us to capitalise on the generous torque curve of the RS24."

"The circuit is also renowned for a very dusty atmosphere. However, this does not give us any major problems as the density of this air-borne pollution is not particularly high, and not significantly different from other circuits during the season."

"One other factor to bear in mind is the comparatively high weight penalty for carrying a heavy fuel load at this circuit (0.41s per 10kg). This means that an engine with good fuel consumption will provide a greater relative advantage than at some other venues."

"Finally, the other factor to be taken into account is the ambient temperature. Of course, this requires special precautions in terms of cooling, but we are familiar with these demands. Rather, high temperatures also have the effect of dislocating an engine's power curve upwards, meaning peak power is produced at higher engine speeds than usual, owing to acoustic changes produced by the lower air density."

"In this respect, the new D-spec engine which will debut at this race will improve the engine power available throughout the rev range as well as allowing us to run higher engine speeds, and will provide an additional advantage in these circumstances."

-renault-

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Series Formula 1