In the upcoming weekend, Formula 1 will make a stop in Mexico at the facility dedicated to the Rodríguez brothers. This track has always been a challenge for the teams’ engineers because the circuit is located at an altitude of 2200 meters above sea level. The thinner air requires the search for maximum aerodynamic load, on the levels of Monaco and Singapore. The lower air density reduces aerodynamic drag, allowing cars to reach very high top speeds. It’s no coincidence that the record for the highest speed in an official Grand Prix session was set on this track in 2016 when Valtteri Bottas’s Williams reached 372.5 km/h.
A performance that is difficult to replicate by the current generation of oversized single-seaters that pay the price due to increased aerodynamic drag.
Now we’ll try to explain in the most intuitive way why the cars will have to adopt high aerodynamic load setups despite the circuit’s geometry lending itself to completely different configurations if it were at sea level. In the following illustration, we have the ideal gas law. It is evident that air pressure is directly proportional to its density. Therefore, a decrease in air pressure corresponds to a lower density. In practice, at high altitudes, the airflow hitting the cars has fewer air molecules, generating lower pressure on the wing surfaces of the cars.
But the unique location of the Mexican Grand Prix presents several other critical issues. The environmental pressure is the lowest of the season (equal to 782mb, note), so oxygen levels are about 78% compared to sea level. This has a significant impact on aerodynamics and power units. Less oxygen in the air means less explosive combustion of the fuel in the ICE (Internal Combustion Engine). It is estimated that every 100 meters above sea level results in a 1% power loss. In the case of the Mexico City circuit, the power reduction for the V6 engines is around 22% of the nominal values. However, the turbocharger compensates for some of the power loss, but not all of it, operating at higher speeds due to the thin air. However, the thin air means that the power unit’s cooling effect is much lower, and the risk of turbo overheating can, in turn, result in a power loss. In short, a real puzzle for the engineers of the teams.
For the Scuderia Ferrari, last season’s race in Mexico was a disaster, probably the worst in terms of performance. The former Team Principal of the Scuderia, Mattia Binotto, pointed to the disappointing performances due to the architectural characteristics of the power unit 066/7: “Regarding the power unit, we knew we would have a disadvantage, but not to justify this performance. The difficulty of the power unit comes from our turbo design that, at that altitude and in that thin air, penalized us more than our competitors.” The Power Unit 066/10 that equips the SF-23 does not differ from that of the previous season, except for the changes made due to the engine freeze (which started on September 1, 2022) that have significantly improved overall reliability. Ferrari’s turbo is not designed to reach 125,000 RPM (revolutions per minute). This is because a small-sized turbocharger was chosen to minimize the turbo lag phenomenon, which is the delay in power delivery by the turbocharger. Probably, this year too, Maranello’s men will have to use a slightly lighter setup compared to the competition to compensate for the lower power output from the power unit.
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Such an aerodynamic configuration could be costly in the race when it will be necessary to manage a car with less vertical load, especially in the stadium section. If, on a clear lap, the softer tire compounds will mask the reduced downforce, tire degradation could be a major concern for Charles Leclerc and Carlos Sainz during the Mexican Grand Prix.
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