Renault Sport share details on fuel thirsty Valencia challenge
A tough track over five kilometres in length, Valencia is notorious from an engine perspective as being one of the most arduous challenges of the season, particularly from the perspective of fuel consumption, as Renault Sport F1’s Head of Trackside Operations, Rémi Taffin , explains.
“Valencia is similar to Melbourne in many ways,” he begins. “There are long straights that end in a lot of first, second and third gear corners, which means you almost stop the car before reapplying full throttle. It’s this succession of constant braking and on, off throttle application that leads to high fuel consumption.
“As an average figure, we usually use 0.5kg of fuel per kilometre. Montreal, which is high on fuel consumption, was about 2.15kg per lap. For Valencia, however, we are around 2.7kg per lap. Obviously it massively depends on the weather, but Valencia is normally sunny and dry so fuel consumption will be at this highest level.
“In Valencia you know you are going to be tight on fuel but the teams are always looking to reduce the size of the fuel cell to optimise packaging elsewhere. The emphasis is therefore placed on the engine manufacturer to reduce consumption as much as possible so the fuel cell can be justifiably decreased in size.
“It’s not as simple as running leaner to use less fuel – that is, running less rich engine mixtures and burning less – as you lose engine performance the leaner you run. It also means the engine reliability is compromised so you fall into a place where you have to weigh up performance and respective gains versus risk.”
Compromise… a word which has cropped up regularly over recent races. But at a track where running to the limit on fuel and using the engine at maximum performance are the keys, how does one begin to find such a happy medium?
“We’re always running engines on the dyno to learn more about the usability of the units. We can still improve consumption on full or partial throttle. We can also optimise the way we use the fuel to slow the car too, for example when downshifting. The engine is ‘blipped’ when the driver shifts down a gear to decelerate, but fuel is still used for this. In fact, this is one of the main areas we can save fuel; clever settings could save around 1% of fuel consumption over the course of the lap, which equates to around 1.5kg over the course of a race – not an insignificant amount when you consider how close the field is this year.”
External factors also have a great effect on the fuel consumption, Rémi explains. “When you get to the eighth race of the season you already have a fairly good bank of data regarding how factors such as tyre degradation and DRS usage affect the rate of consumption, particularly bearing in mind that going from qualifying to the race we switch from fresh tyres to used tyres and potentially from full DRS to one straight line DRS. The difference in using DRS on the main straight or not at Montreal, for example, was worth 2 to 3% of fuel over a lap.
“To get the optimum performance over a race distance, we don’t necessarily use the richer settings all the time. As an example, in the last 20 laps of a race, running the leanest mode as opposed to a performance mode could save you 5kg of fuel at the start of the race, which is worth around 0.2s per lap.
“We can also burn more fuel if required, should we find we get stuck behind traffic or after a safety car period. In this instance we have excess fuel, so we attempt to burn this surplus to bring the car down to the planned weight. You can either burn it off quickly, or avoid switching to the leaner engine modes until later in the race, if at all.
“The choice will depend on how the race strategy unfolds. You have to work out where you want to be quickest; is it in the first part of the race, the middle part, or the end? It all depends on your strategy and where you think you will be on track, what battles you will be involved in, and when you will be pitting and what tyres you will be on. This strategic decision will impact not only the starting fuel load but also when and how you use that fuel.
“Normally you will always run the leanest at the end of the race, just because you try to gain track position in the first part of the Grand Prix. You look at the long term plan and you say, ‘OK, our target is to stop on lap 50 for the last pit stop,’ so you will need to run as fast as you can in the early part of the race to get the best position by the time you stop. As a result you want to run the engine at maximum performance with the lightest car. Therefore, your strategy will tend to push you towards using the richest setting to start with before switching to a very lean setting in the end.
“However, if your strategy works, you could also have to defend your position at the same time you are running in a lean mode…which is obviously not ideal. There are certain things you can do though to help, such as you do not need to run the same mixture setting all around the lap. You could, for instance, run lean round the corners and then opt for performance setting in the main straight: in this respect, using fuel settings becomes very similar to how you would use KERS to defend.”
In short, teams optimise the fuel put in the car to be fast according to individual strategy. “A good example of this is Romain Grosjean’s race in Canada,” continues Rémi. “He ran different settings throughout the race and depending on the race conditions adapted the settings to stick to the primary strategy and always get the fastest car. The team played the long game, and it all worked out perfectly for him.”
Courtesty of Renault Sport F1
