Sunday, 8 June 2014

So what about Porsche?

My last post about the Le Mans Test day failed to mention the new Porsche 919 Hybrid. Deliberately so, for I had the feeling at the Test that Porsche was ignoring everyone else and getting on with their programme. Although it makes sense to look at their performance at the Test day in isolation, we are, after all, looking forward to a motor race; and the purpose of a race is to compare yourself with the opposition. But regardless of the objective, let's have a closer look at Porsche's Test Day.

Porsche has, arguably, the most advanced hybrid system of all: a front-axle kinetic and an exhaust gas-driven turbine feeding energy into water-cooled, lithium-ion batteries. This provides much greater energy than Audi can achieve, and delivers the power much more flexibly than Toyota. The small-capacity engine can be boosted whenever the engineers have the fuel available to them, providing the team with the ability to make the most of opportunities that might arise.

We saw at Silverstone and Spa how fast the Porsches were; they are also economical. If any car in the LMP1-H class has the ability to manage 14 laps, then it is for sure the Porsche. The fact that they did not go that far during the Test Day is surely irrelevant. Toyota may also go 14 laps come the race, but they may have to shave ultimate performance to achieve that. Porsche will be able to complete 14 laps at full power.

How fast is fast? Here are the top speeds, measured at the speed trap located just before the first chicane on the Mulsanne straight.

No. Car        Top Speed         Average top speed
1 Audi 333.9 325.5
2 Audi 332.9 326.1
3 Audi 332.9 321.8
7 Toyota 334.9 320.1
8 Toyota 336.0 318.4
12 Rebellion           326.8 322.4
13 Rebellion 331.8 323.3
14 Porsche 332.9 323.7
20 Porsche 339.1 330.3

The ‘average’ top speed is the average of the best 25 speeds recorded - removing the effect of any ‘bansai’ lappery or trickery to gain bragging rights.

The main conclusion to be drawn from this is that the two Porsches had very different programmes. I don’t think that is particularly surprising in the circumstances, but what is interesting is that the two cars finished the day separated by just a quarter of a second in terms of best lap, and the ‘ideal lap’ i.e. the one achieved by taking the sum of the best three sector times, for the no. 14 Porsche was within a hundredth of a second of that of the no. 2 Audi.

Porsche may be in only its third race, but it has spent a long time testing, and should, by now, know what it is doing. Reliability may be an issue, but then this technology is so new that Toyota must have similar concerns, and even Audi’s bullet-proof reputation puts it at risk.

The other thing to consider is going to be the time spent in the pits. Even though Michelin is providing tyres to Porsche, Audi and Toyota, it will be interesting to see if they all are able to make the tyres last the same. The more potent Toyota may find that tyre wear is more of an issue. And of course this is the area in which all the teams were concentrating at the test. And they won't tell us (at this stage) what they have learned!

I don’t expect Porsche to participate in what is undoubtedly going to be a no-holds barred battle at the front in the opening few hours, but I do expect them to get on with the job quietly and efficiently, and if they can stay out of trouble, they will certainly be a feature when the sun comes up next Sunday morning.

I’ve said it before; but it bears repetition: Toyota is the favourite for this year’s 24 hours, but if they are not perfect - on the track and in the pits - then they cannot expect to win.


  1. Hi Paul,
    Great stuff as usual. I have been an avid reader of this blog for some time now and have a great respect for your opinions and analysys. But your last 2 posts (and other things I have read) have left me confused.

    From what I understand each car has a maximum amount of energy it can use for a lap of Le Mans.
    Porsche & Toyota get 139.5mJ and Audi 138.7.
    Porsche & Toyota get a maximum of 6mJ from recovery systems and Audi 2mJ.

    So am I right in thinking that Porsche & Toyota produce 133.5mJ from their petrol engines and 6mJ from recovery systems giving them 139.5mJ. Whist Audi produce 136.7 from their diesel engine and 2 mJ from recovery?

    So we are looking at a very small difference of 0.8mJ per lap, which by my sums is slightly less than 1%. Especially when you divide that 0.8mJ between the number of corners. If there was only 8 corners at Le Mans that’s an additional 0.1 mJ per corner. So how on earth are Toyota getting so much more acceleration? And how does all this fit in with the figures floating around the internet that Toyota have about 230 bhp more than Audi with Porsche somewhere in the middle?

    If Toyota are using a greater % of their total allowance for acceleration, once that has been used they should be left with a slightly less powerful engine. So how come they appear to be faster down a long straight? The difference at Spa was staggering!

    It seems to me either some of these teams are generating massive amounts more than their maximum or Audi are nowhere near theirs.

    One other thing.
    This 0.8mj per lap seems very small until you multiply it up.

    With the new Slow Zones system I think it is fair to assume that there will be very few safety car periods. So a new distance record could well be on the cards.
    Lets assume they do 390 laps. 390 x 0.8= 312mJ. Or enough for more than 2 laps.
    And if your sums are correct (I don’t doubt it!) Porsche & Toyota should be able to do 14 laps to Audis 13 per tank of fuel. So 27 stops for Toyota and Porsche and 30 for Audi.
    Oh dear, they had may as well of told Audi to give the others a 5 lap lead! And there was me thinking all these new rules were designed to equalize petrol/diesel!

    1. Dave,

      Fundamentally, you're right on all counts. The only bit you miss is that electric is much more efficient than a combustion engine, so can convert the energy to kinetic better. This is where the Toyota's acceleration is coming from (and Porsche's).

      The problem for Toyota is that by the end of the straight bits, the electric energy is beginning to wane, so its speed will tail off towards the end of the straight, whereas Audi and Porsche will be able to maintain their speed (although reach top speed more slowly).

      But yes, it is complicated, and hopefully new rules when they are introduced, will be simpler.