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Tech Spec – The McLaren telemetry Spa-ga - A closer look at the straight lines and squiggles of some unexpected data

Published by Will Davies

Lewis Hamilton’s Twitter-sode over the Spa weekend left us with a lot to think about. Not just his openness and insight, but also his frustration, and some less-than family-friendly language – all in an attempt at justification for his ‘poor’ qualifying.

Possibly the best thing that came out of all this was the Instagram photograph – a comparison of Jenson Button’s telemetry for the Pole-lap, with his own. Now I don’t claim to be able to read these, let alone correctly, but I’d like to try to pull apart the information that is hidden behind the ‘squiggles’.

What does it all mean

I’ll start by (trying to) work out which ‘squiggle’ means what. The first thing that we can see is that all these data are represented against the distance (on the x-axis) around the lap – beginning at the SF-line (0m), Eau Rouge is around 1100m and finishes back again at 7004m. Secondly we need to note that for each ‘squiggle’ there are two different traces – one is Jenson’s data, while the other is Lewis’.

A good place to start would be the top line – that is DRS state, with the lower line indicating that the wing was closed, and the raised sections showing that the drivers had the device activated. I was rather confused as to what this was, until I remembered about the ban up Eau Rouge – then it become obvious. We can see that both drivers are using the DRS in almost identical places – which I’d imagine comes from hours in the simulator. I’m actually a little disappointed that Lewis didn’t manage to take a photo of the whole page – as we’re missing KERS usage data.

McLaren telemetry

The second set of lines is quite simple – car speed – the higher the line, the faster the car at that point of the lap. We can clearly see that JB (top line) manages to reach a higher speed than LH, at the end of the straights (1). Further down the page we can see a stepped trace – showing which gear the cars are in. Although the drivers seem to be using the gears fairly similarly, we can see that LH has to shift ever so slightly after JB. We can put this down to LH’s choice of rear wing. The higher down-force wing that he was so aggrieved to have chosen has slowed his straight-line speed – meaning his up-shifts have been delayed accordingly (2). Another possible / contributing reason for the slower acceleration might be that LH’s gearings would’ve (probably) been optimised for use with the other wing.

The dotted line that has usefully been annotated for us is the time delta between the two drivers – the higher the line, the closer LH is to JB's time, as vice versa. You can even notice that he’s ahead at around 5000m through the lap (3). It is clear that on the straights he does lose time (probably down to the wing), but that is not the whole story.

Just above (and overlapping slightly) the speed-trace is the steering angle, with left being represented downwards, and right upwards – for reference, I’ve marked the La Source hairpin. For most of the lap there is no real difference between the drivers, which is what you’d expect from top drivers. However, you can make out that LH lost some time in Les Coombes (2600m) – it looks like he had understeer (4) and his trace shows a mid corner correction.

At the bottom of the page there are the traces for both percentage of throttle and brake pressure.

Further conclusions

Apart from what can be gleaned from the traces when taken individually, closer consideration of a few together can lead to further conclusions.

For a start, LH’s higher wing wasn’t quite as much of a hindrance as he’d like us to believe. He gains back time on JB under braking, and through the corners – having more downforce meant that he could brake later, as well as carry more speed through the corners – because his car had more force ‘holding it on the track’. This is most likely the reason that LH matches JB on the run down the hill to Bruxelles, so he’s not losing much time there (5).

At the final chicane, the Bus-Stop as was, LH was much better on the brakes – able to apply more pressure without the risk of locking his wheels (6). He gains so much time that the printout shows that he manages to get himself ahead of JB (7). If you watch the BBC’s side-by-side running of their laps, this isn’t the case, so it looks like the scale for that trace is misaligned slightly.

This doesn’t diminish from the gains that he made, and although his run to the line would’ve inevitably been slower, he could still have had enough in the bank to have gone P1.

It is also worth spotting that LH manages to (almost) match JB’s speed at the end of later straights. I feel that this is somewhat to do with the trade-off that the higher downforce wing brings. Although it may mean that a car is producing more drag (a factor in slowing acceleration), as mentioned before, by carrying more speed through the preceding corner (8) means that you get a ‘head start’ in the acceleration on that straight – and ultimately meaning that he doesn’t lose as much as you might first expect.

And finally

Lewis may have achieved his aim of illustrating that he was hindered on the straights by his choice of wing, however he’s also shown us that he could’ve still been on pole. He gained the time back by being able to take the corners at a faster speed (9), and it is in fact the mistakes that he made that cost him the places on the grid.

Maybe next time (not that there’ll be another Twittergate quite like this) he’ll read his telemetry more closely before publishing it for his own means – to justify his ‘slow’ lap, as all he’s done is highlight what might’ve been.

And if Lewis or anyone from McLaren is reading this, more printouts please – these are great. Oh, and also feel free to put me right on anything I’ve misinterpreted.

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