There has been a lot of chatter in recent days, following the publication by the ACO of the Performance Adjustments in advance of the Le Mans 24 hours, for which scrutineering is due to begin in just two weeks time. My sympathies lie with all concerned. First, with the ACO, who is coming under criticism for doing ‘too little, too late’. Second, with the smaller teams who now have very little time to test out different engine mappings and the impact on fuel consumption and tyre wear of running with less weight and more power. And third with the major manufacturers, whose advantage over the rest has (to an extent still to be determined) been diminished.
For the spectators and media though, it can only be good news. The media can now go into a frenzy of claim and counter-claim and the spectators have the prospect of a closer race to witness, with all kinds of possibilities now in prospect for the great race.
The detail of the adjustments can be found elsewhere on the web and if you are savvy enough to get here, then you’ll be able to read the exact changes that have been mandated. I also commend to you the interview (published both in English and French) with Vincent Beaumesnil (sporting manager of the ACO) justifying the adjustments. My purpose here is merely to comment.
First, a defence of the ACO. Article 1.3 of the 2011 Sporting Regulations (first issued in December 2010) was clear enough: the adjustments would be applied to ‘the slower technologies’ and there was no suggestion that the faster cars would be ‘reeled in’. So the idea that the ACO was going to adjust the performance of the diesels to slow them down to the ‘target lap time’ of 3 mins 30 secs was never (in my opinion) an objective for the ACO. I’ll admit that it was their stated objective when the Technical Regulations were written in the first place, but not the objective of the mid-season performance adjustment.
So suggestions that the ACO missed an opportunity to slow down the diesels are, quite simply, wrong.
It was equally obvious therefore that the impact of the performance adjustment would fall on the teams using the slower technologies. So the time to complain was in December and January (or in the many meetings that the ACO held with Le Mans entrants beforehand), not now that the actual adjustments are made known.
The regulations also made clear that only race data would be analysed, and adjustments would only be made after two races had taken place. Sebring and Spa were the first two rounds of the ILMC, but the ACO also had the chance to analyse data from Long Beach (ALMS) and Paul Ricard (LMS), but of course there were no diesel-engined cars at either of these events. Data from practice and qualifying sessions, and the Le Mans Test Day was inadmissible. From looking at the calendar, it was apparent that time would be tight between the data being available to analyse and the outcome of the organiser’s deliberations being made known.
The way I look at it - and for the moment focussing purely on LMP1 cars, the adjustments fall into two categories: firstly the diameter of the refuelling hose (or at least the orifice through which the fuel has to pass) and secondly the engine performance parameters.
The diameter of the refuelling hose obviously has no impact on lap times, but will affect the amount of time spent in the pits refuelling. Now I am no expert at fluid dynamics (I believe the term is rheology), but by reducing the size of the orifice through which the fuel must flow for the diesels by 3mm (to 25mm) and by increasing it for the petrol-powered teams by 10mm (to 38mm), the ACO has made a significant impact, without demanding the teams to make any change to the configuration of the car itself.
By my somewhat rough and ready calculation, the fuel flow rate for the diesels will be roughly half that for petrol-engined cars. In other words, petrol will flow (less viscosity, through a larger restrictor) at a rate of nearly 3 litres per second, but for the diesels at about 1½ litres per second. This will mean that a fuel-only stop will cost a petrol team 25 seconds (depending on how much fuel is left in the tank when the car stops), whereas a diesel car will be at rest for around 50 seconds.
Reassuringly, I did this calculation before reading the interview with Beaumesnil, who also suggested that the difference in refuelling time would be “over 22 seconds, the equivalent of two seconds a lap”. Over the course of 24 hours, this is like giving a diesel car around three and a half laps penalty. If that’s not “reeling in the diesels”, then what is?
The other category of change is the reduced weight / increased air restrictor combination, and this is what leads me to sympathise with the petrol-fuelled privateers. It’s now decision-time. Run at the reduced weight and risk a problem occurring in the race that hasn’t previously been encountered? Maybe the car is not at the weight limit anyway; in which case, the increased restrictor could mean additional engine development costs and changed mappings. But doing nothing is not really an option either - the extra air entering the engine should provide enough horsepower to reduce lap-times by up to a couple of seconds. But would Pescarolo or Rebellion (for example) want to come to Le Mans with a different package from the Test Day without proper testing? It is a real dilemma.
The trouble with all this performance fiddling, is that it makes comparisons difficult. Lap times obviously can’t be compared from last year to this, but nor really can pit stop times. “Time spent in pits” is one of those interesting statistics that I collect. But when I look back at the amount of time spent by cars in the pits over the years, I find myself increasingly comparing apples with pears. In the days of Group C, the fuel fill rate was one litre per second, and the tank (under the first iteration of the regulations), took two minutes to fill. More recently, the nonsense with the restrictions on the number of mechanics changing the tyres has made it meaningless to compare pit stop times with those from the early years of this decade.
This year, however, the fact that fuel is allowed to flow into some cars more quickly than others, will make "time spent in pits" even more irrelevant as a measure of a team's efficiency - although it may well have a bearing on the outcome of the race.
There are other aspects of the adjustments which also bear discussion, such as the reduced weight of the Oreca Peugeot (yes, the one that won at Sebring) and the LMP2 changes (which seem to penalise the slower cars), but I think I will leave those for another occasion.
What do you think?