Under pressure
Racecar Engineering|December 2021
Toyota may have finished first and second at Le Mans this year, but the effort required to overcome a fuel delivery problem and finish with both cars was Herculean
ANDREW COTTON

The history books will show Toyota dominated the 2021 running of Le Mans, with opposition coming from a year-old Alpine that was hamstrung by regulations, and two Glickenhaus LMH cars that were in their first year of competition.

The GR010s finished four laps clear of the Alpine in third position, but after the race the Toyota team members were exhausted, both mentally and physically. The effort it took to bring both cars to the flag was little short of miraculous, as both cars suffered blocked fuel filters that threatened to retire them at any point in the last eight hours of the 24-hour race.

From the outside, it was clear the cars were nursing a problem as they were not running full-length stints on the fuel. At times, the cars were pitting every three laps, which put incredible strain on the team in the pit, and also lost valuable track time.

Onboard cameras also showed the drivers were pressing a set sequence of buttons at various points around the lap. At their most vulnerable point they were switching to 'DD7.3, a setting on the steering wheel that was broadcast to the outside world, in every one of the six major braking zones around the lap. What they were in fact doing was switching off the fuel pump when it was not loaded under braking, and then re-activating it when acceleration was required from corner exit in a bid to maintain engine performance.

'At 8am on Sunday, there was no one who knew about the problem who would have bet that we would be there at the end, admitted team principal, Pascal Vasselon, after the race.

The entire team was involved in either brainstorming to find a solution, or running the cars, but underlying the whole final third of the race was the fear they would lose one or both cars through a fuel starvation misfire.

This is the story of the race, Toyota's mission to analyse the problem whilst running at race pace, find a workaround for an unstable issue and, ultimately, bring its two cars to the flag.

The problem

The opening round of the FIA World Endurance Championship at Spa in May was the race debut for the Toyota GRO10s, and they were not without problems. One of the two cars had only just been shaken down prior to arriving in time for the pre-season test, and the team spent much of the weekend working around various electrical and hydraulic issues. The other had completed much of the pre-season testing so had been largely de-bugged.

After bringing both cars to the flag there, in first and third places, the team worked hard to improve them for the second race at Portimao. The cars ran well in Portugal and so it was with a little more confidence that the team arrived for the third race in Monza.

However, the Italian race provided an indication that the cars were still vulnerable. The number seven car had stopped for a system re-set on its way to victory, but there were far more issues for the number eight car, which suffered from a clogged fuel filter, which was at times starving the engine of fuel, leading to a misfire.

Brendon Hartley was at the wheel when the problem became so great the team had to pit the car and change the collector at the bottom of the fuel tank. The fix took 45 minutes, but a mistake in the pits meant the front left wheel was not properly re-attached, and in braking for the first corner the car went off, Hartley again the innocent passenger.

Toyota took a close look at the fuel system of the number eight car to work out why the filter had become blocked, and almost immediately hit on a reason.

'The blockage of the filter came from two things explains Vasselon. 'The first, and most critical, one was a grease that was present in excess in the refuelling connector on the car where the nozzle connects. This is serviced every year at the supplier, and the connectors came back with a lot of grease. This grease did not dissolve in the fuel and was going around [the tank). But this grease alone was not enough (to cause the blockage). The grease was able to go through the filter.

'What happened in Monza was that this grease collected aluminium oxide particles that were present in the fuel machines. We had new fuel machines in Monza that were not completely clean inside, and were generating aluminium oxide particles. This is how we concluded we were certain to have found the problem!

The fuel storage tanks were new at the start of the season and had not presented this problem in testing, or at the opening race, so it was with some surprise that the team found the issue post-Monza.

'We never found this issue in testing/ confirms Vasselon.'It takes time to clog the filter, it doesn't happen in three laps. You need the grease to collect the particles, and the particles came from the machines we don't always use. We got these ones for the Prologue in Spa, so there was not so much mileage on them!

Confident arrival

The team therefore arrived at Le Mans convinced it had identified and solved the fuel issue by cleaning the machines properly, and senior management was robust in its defence when questioned prior to the race.

Privately, however, there were members of the team that were not convinced the problem was completely resolved.

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