Mercedes were finally beaten to the chequered flag on Sunday, to the great relief of F1 fans everywhere I'm sure. In this post I'll show you some details in the RaceTrace™ for the Malaysian Grand Prix which hint at how Ferrari managed to win with probably the second fastest car.
If you haven't seen the RaceTrace™ before, it's a chart showing each car as a line starting at the left at lap zero (the start) and progressing to the right as laps are completed. The vertical axis is time and the horizontal axis is distance (number of laps), so the slope of a line is determined by the laptime of the car. To make things a little bit harder to describe, but a lot easier to see, the time axis is not simply time since the start of the race but rather time relative to an imaginary reference car which doesn't make pitstops. To see the difference have a look at the plots below:
As you can see, the raw times don't tell you much whereas the time relative to a constant-paced reference car really shows you what happened in the race. Now if we just focus on Ferrari and Mercedes we can get some insight into how Vettel managed to win the race, fig. 3 shows just the two main protagonists, Ferrari and Mercedes:
You can see that when the safety car came out the two Mercedes dropped down the order and got stuck in some traffic while Seb drove off into the distance, and you can see that all three front-runners stopped twice after the safety car. You will also notice that the line gets steeper after each pit-stop and the lines at the end are much steeper than at the beginning – this is due to fuel-effect. Every lap the cars use about 1.8kg of fuel, and each kg of mass on the car slows it down by about 0.03s/lap, so every lap the cars get lighter and faster, by about 0.054s/lap at this track. Meanwhile the tyres are getting worn out lap by lap and making the cars slower, this is tyre degradation or tyre deg, or simply deg (engineers are not verbose people on the whole). So if tyre deg is bigger than fuel-effect then the lines for each stint will tend to curve downwards as the car gets slower each lap. If deg and fuel-effect are equal then the lines will be relatively straight and change slope at the pit-stops (as in Vettel's last stint). The thing is, fuel-effect isn't really interesting, it affects all cars to roughly the same extent and it doesn't really contribute to the strategic picture, so we'd like to get rid of it and see the effects of tyre deg on their own. To do this we simply change the reference car to have its own fuel effect; instead of showing time relative to a car doing constant lap times, we show time relative to a car going 0.054s/lap faster every lap. Fig. 4 shows the fuel-corrected version of the RaceTrace™ from fig. 3:
This fuel-corrected RaceTrace™ shows us the tyre deg much more clearly and we can start to see how much gentler on the tyres Seb is than the Mercedes by how little his trace curves downwards compared to the traces of the Mercs. Bear in mind that the Mercs had fresh tyres coming out of the safety car period and so made three stops in total to Vettel's two. Another thing we can discern from this is that Mercedes pit-stop strategy was not as good as Ferrari's, their second stint was too long. We know this from looking at the slope of the fuel-corrected traces just before each pit-stop: Vettel's line has pretty much the same slope before each pit-stop, meaning the same fuel-corrected lap time before each stop and hence the same amount of deg on each set of tyres. The Mercedes on the other hand have a much more downward slope before the second stop than before the third – this means that they used the second set of tyres a lot more than the third set and that if they had done fewer laps on the second stint and more laps in the third stint they would have reached the chequered flag sooner. Fig. 5 zooms in on the post-safety car stints and highlights the slopes of the three lines at the ends of each stint:
This was a very interesting race, strategically-speaking, we have seen from the RaceTrace™ that Ferrari nailed it and Mercedes got their tyre deg estimates wrong. If they hadn't got stuck in traffic under the safety car it would have been a very close race indeed!