The Renault-driven cars experienced a series of technical gremlins over the entire race weekend of the Mexican GP. The French manufacturer managed to find the cause of the technical woes right after the race and hopes they won't repeat themselves in the next two GPs.
The Renault-driven Red Bull won the race, four Renault-driven cars qualified in the top 10 during the qualifying session. This string of successes came on a track where engine performance makes a huge difference due to the long straights. This indicated that Renault could make big leaps and strides with its power unit over the last weeks.Engine woes at all Renault-driven teams
However, that performance improvement made damage to the much improved reliability of Renault’s power unit. Toro Rosso had a series of issues on the turbocharger and the MGU-H over the practice sessions. Pierry Gasly could complete only 12 laps in the practice sessions. Brandon Hartely was forced to retire from the race.
After a less successful qualifying, Daniel Ricciardo got a new internal combustion engine, a new turbocharger and a new MGU-H. The Australian was seemingly happy with that precautionary change of components, because he hoped that he can fill up his pool for the remaining two GP weekends. Despite to the fresh elements, the 5-time GP winner could only cover 35kms in the race. The connection between the turbocharger and the the MGU-H broke after that short distance.
The works team Renault had also problems to cope with in the race. Nico Hülkenberg charged for a point-scoring finish which would have helped the French team in its battle with Williams in the Constructors’ Championship. The German was, however, warned and instructed to park his car on lap 25. “Stop immediately. The car is not safe anymore”. The word ‘safe’ in that context has the meaning in the double-hybrid era that the car is under electric current. After a thorough inspection, the Renault engineers could not detect an actual issue, so the warning was only a precautionary one. However, every team follows strict rules in that regard to guarantee maximum safety to their drivers.The root cause of the problems
Renault confirmed that it made a miscalculation in terms of the balance between the performance and reliability while preparing for the Hermanos Rodriguez track. The track lies 2240m above the sea level which is significantly higher than the Sao Paolo circuit which is the second in that ranking with its altitude of 800m.
The altitude means that the air is much thinner. The less oxygen causes problems for the internal combustion engine during its combustion phase. To balance that out, the turbocharger has to work much harder to blow more oxygen into the combustion chamber. The more intense work for the turbocharger, however, means that it runs in higher operating temperatures which can shorten its life.
Renault let its turbochargers run at 108.000/min at the beginning of the weekend. As the engineers found out after the early issues experienced during the practice sessions that this running value it too high, the rev speed was decreased to 102.000/min for the race. This decrease meant a loss of 0.15 of a second in pure lap time.
Interestingly, Ferrari could run its turbochargers at the maximum of 125.000/min while Mercedes was only a tiny bit below that limit.
According to the information of the highly respected German journalist Michael Schmidt, Daniel Ricciardo and Brandon Harley will be forced to put new elements again in their pool of engine components in the forthcoming Brazilian GP which will put them further back on the grid due to the subsequent penalties.