Malaysian Grand Prix: Strategy Predictions

Posted on March 22, 2012

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Given last year’s race, the immediate guess will be that the majority of cars will look to stop three times, and that there will be a few midfield teams who will aim to stop twice. Well, I’ve done my homework in analysing the 2011 race, and although there are differences in the tyres from last year (the hard tyres are softer and the soft tyres are medium), there are useful things which can help to know what to look for. The idea of this post is to go through the possibilities, and to point out what we might be able to find in the data from the Friday (and Saturday) running to give us some clues about both the relative pace of the cars, and the potential strategies.

So what do we learn from last year. Well, first off, what is the likely pace of the opening laps? Vettel’s opening stint was run at a pace of about 104.2s per lap – with the tyre degradation offsetting the fuel burn off (about 0.09s per lap fits well) closely enough that it’s a good enough model. You could argue for a slightly higher initial degradation, and that the lap times gradually deteriorate, but the difference is small enough that it doesn’t affect the analysis in a material way. So if the tyres are performing in a similar way, we would expect to see long runs in Free Practice 2 which are run at close to constant pace (for a number of laps – how many is key) – with a full fuel load pace being slightly slower than Vettel’s pace from 2011. This is based on the pace being of the order of 0.6s slower at Melbourne in comparison with the previous year, which is all we have to go on. It may mislead, but it’s the best guess we can make. This should provide some idea of who is running a full fuel load, and who is not.

Secondly, the impact of running new or used tyres was about 0.3s for the soft compound, and significantly more for the hard compound last year. As the tyre compounds have changed for this year, and the tyres available are the medium (reasonably close to the soft from last year) and the hard (softer than the medium from last year), we will go with the 0.3s penalty for used tyres as a best guess. The pace gap between the tyre compounds was around the one second per lap mark (ranges from 0.8s-1.2s for most cars) last year, so we would expect something smaller this year. However, the most important aspect of the tyres was the lifetime. The softer tyres entered a ‘phase 2’ degradation after (depending on the car and fuel load) after between 9 and 15 laps, and the severity of this non-linear extra degradation varied between about 0.6s per lap and a full second per lap. There is quite a big variation here, and it is this aspect that is likely (if indeed this ‘phase 2’ degradation is a probelm at all) to determine the pitstop strategy. The hard tyres did better, but 20 laps was about all they managed.

So, for an initial set of simulations, we will use a pace difference between the tyre compounds of 0.5s per lap, a used tyre penalty of 0.3s per lap and no ‘phase 2’ degradation issues. We will also assume that there are new new softer (option) tyres, and two sets of new harder (prime) tyres. The time loss for a pitstop at Sepang is of the order of 22s-23s, so we will use 23s. From this we get the following idealised race history chart.

And we find that two stops is the winner, but with three stops less than 10s slower. One stop is (perhaps surprisingly) competitive. It is worth noting that the penalty for running mediums for two stints is under four seconds.

But look what happens if we put in some ‘phase 2’ degradation. Let’s start with 12 laps for the mediums, and 15 laps for the hards, say, with a ‘phase 2’ penalty of 0.6s additional per lap. This would be roughly in line with last year’s data, although the tyre lifetimes are guesswork – more clues should be given from the practices on Friday.

 

Now one stop is properly uncompetitive (and thus ignored), and three stops is more than ten seconds faster than two stops, with running on the harder tyre preferable for the longer lifetime. Four stops also comes into the picture now, and is competitive. This goes to show how important it is to avoid the ‘phase 2’ issues. Therefore, it is the lifetime of the tyre before the degradation becomes severe which is the driving factor in the strategy. Whether the teams will allow the long runs to be long enough for us to see how their cars are using the tyres (you could see it in Japan last year, but it wasn’t visible in the data from Brazil), or whether we need to glean bits of information from Pirelli to give an idea of the lifetimes is yet to be seen. But if the first stops are much past lap 10, then three stops should be OK; if we get to lap 15, then it could well be two – and that would be a surprise.

Having done all this, what are the chances of a wet race?

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