F1, Ferrari: SF-23 power unit tuned down in Mexico City GP to avoid overheating. Ferrari lost 20 km/h lost from Saturday to Sunday in Mexico City.

After brilliantly securing the entire front row in the qualifying session for the 2023 Formula 1 Mexican Grand Prix, the engineers at Scuderia Ferrari had to settle for third and fourth places for Charles Leclerc and Carlos Sainz due to the inherent issues with the SF-23. Tire wear prevented the red cars from containing the performance of Hamilton, who finished second in the Mercedes. However, more than 20 km/h lost from Saturday to Sunday to prevent the 066/10 power unit from overheating also played a part in the result.

Ferrari had plans to gain significant points on Mercedes, and at the end of the Mexican GP, the team should be content if they concluded with a tie in the Constructors’ Championship for the second place.

After Charles Leclerc’s pole position and an all-red front row with Carlos Sainz, one could expect more than just a podium for the Monegasque and a fourth place for the Spaniard. Perhaps not to challenge Max Verstappen’s 16th victory, but at least to compete for Lewis Hamilton’s second place.

At the 4.304-kilometre Autodromo Hermanos Rodriguez in Mexico City on Sunday, we witnessed the SF-23 in a somewhat different light. It was extraordinary, even elusive, in a single qualifying lap, but it displayed less race performance. This characteristic is not new for the Maranello team’s car, accentuated by Mexico City’s altitude and the thin air at the 2,200 meters of altitude at the Tenochtitlan plateau.

Ferrari’s engineers had prepared for this tricky race, following last year’s experience when they had to significantly reduce the power unit’s output to ensure reliability.

Ferrari had indeed been one of the most open cars aerodynamically among the top teams. The aerodynamicists were aware that on a track where speeds exceed those of Monza (Valtteri Bottas reached 361.9 km/h with the Alfa Romeo C43 fitted with the Ferrari 066/10 engine), they would have to use maximum downforce with Monaco-style wings. Sacrificing some efficiency to open up cooling ducts shouldn’t have been a major issue.

For Mexico City, Ferrari designed a bodywork with various heat outlets, not only in the engine cover’s root area but also in the trench that remained at the top of the sidepods. It should be noted that an asymmetrical configuration was chosen.

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As shown in Giorgio Piola’s image, there were six vents on the left side that climbed from the sidepod up to the engine cover’s flat portion. These were enlarged openings that easily revealed the mechanics underneath. On the same side, in the initial part of the trench, there were five more horizontal hot air outlets that were not seen on the right side. On the right side, even on the engine cover, only four “windows” were counted because two were closed.

Red Bull and Mercedes adjusted their cooling systems but without going to the extreme of the Scuderia. On the RB19, we counted four vents on each side at the edges of the sidepods and about ten gills on the engine cover, with considerably smaller openings. The Silver Arrow retained three small openings in the horizontal recess of the engine cover bazooka and used a grid of about ten vents at the upper edge of the sidepod.

Although Ferrari wanted to keep things under control, the Maranello team had to deal with the Mexican heat and thin air. As early as the third lap of the 71-lap race, the Maranello pit wall radioed Charles Leclerc to “lift and coast” on the long straights because the power unit temperatures needed monitoring.

The telemetry graph, comparing Charles Leclerc’s pole lap and the 16th race lap (chosen as a sample), shows significant differences. Obviously, the performance on a clear lap with an almost empty tank and new soft tires is not comparable to a race lap with a full fuel load and medium tires. Therefore, we’ll avoid discussing lap times, focusing our analysis on some parameters that are highly indicative of the car’s behavior.

Il confronto

The comparison should not be made in absolute terms, but by taking some interesting points of analysis. The most noticeable one is the top speeds: in Q3, Charles Leclerc reached a peak of 350.7 km/h, while in the race, he didn’t exceed 330.5 km/h. A 20.2 km/h difference was significant because he was fifth in the speed trap chart in qualifying and plummeted to 19th in the race. Carlos Sainz, who finished fourth, touched slightly higher speeds at 333.5 km/h.

What’s noteworthy here is that the Ferrari customer cars with Ferrari engines had significantly higher top speeds: Valtteri Bottas topped the speed trap with the Alfa Romeo C43, reaching 361.9 km/h, while Guanyu Zhou in the sister car reached 353.6 km/h. The two Haas cars of Nico Hulkenberg and Kevin Magnussen hit 359 and 357 km/h, respectively. For comparison, Max Verstappen, the race winner with the Red Bull RB19, reached 354.0 km/h, while Lewis Hamilton reached 349.2 km/h.

The difference in speeds between Ferrari and all the other cars was striking. It signaled something was not going as planned, as in the stunning qualifying lap. Telemetry reveals more informative data, beyond the speed trap readings. If we look at the engine revs graph (third one from the bottom, RPM), we can see that the limiter was not hit because the gearshifts reached the rev peak, but the drivers frequently didn’t utilize the full power of the 066/10 unit. Instead, they opted for defensive strategies to control engine temperatures.

Moreover, during the three long straights at the Mexico City circuit, by observing the white line of the throttle (Throttle), it’s evident that it was released much earlier compared to the qualifying lap. This signifies there was a premature release to favor “lift and coast.”

Naturally, we must add tire behavior to the engine parameters in our analysis. The soft tire in qualifying partly covered the SF-23’s setup deficiencies, which, however, became evident in both race stints.

With the yellow tires, Charles Leclerc and Carlos Sainz defended well (they were about 5.5 seconds behind Max Verstappen), but the same can’t be said after the restart on lap 37 following the red flag. With the hard tires, the two Ferraris struggled more, and Lewis Hamilton’s pace became unstoppable, especially since the Englishman took the risk of using the yellow tires, covering a distance the red cars wouldn’t have reached.

The combined effect (thin air, engine, and tires) forced the Maranello’s drivers to settle, and at the end of the investigation, Charles Leclerc’s third place, followed by Carlos Sainz, is not even that bad given the circumstances. Moreover, at the end of the race, the drivers were instructed to move more rearward with the brake balance because the front discs began to reach temperatures close to the limit.

Ferrari concluded the Mexican GP with a points haul that was not as expected. This weekend, the circus moves to Interlagos for the Brazilian GP, another track at altitude (about 700 meters, not 2,200 like Mexico City). F1 arrives on a circuit that seems quite suitable for the W14 (the Silver Arrow had a double win there last year), and Ferrari can’t afford any more mistakes if they still have ambitions to aim for the second place in the Constructors’ Championship.

One thing is certain: the use of a fifth engine is not expected on the São Paulo track, a sign that the preventive work carried out in Mexico has yielded results. Contrary to certain reports, the Scuderia should conclude the season without needing an additional unit for which they would face penalties…