How did Alfa Romeo turn the C42 into a formidable midfield contender in 2022? Mark Hughes looks at the changes that see the Swiss-based team sit fifth ahead of the Miami Grand Prix.
Alfa Romeo have been making significant progress of late and, at Imola, only a lost nine seconds in the pit lane to a cross-threaded wheel nut cost Valtteri Bottas a genuine shot at the podium. Rejoining after that problem, he quickly eradicated an 11s deficit to George Russell’s Mercedes and, had he been able to pass, he may have had the pace to have challenged Lando Norris’ third place.
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This came in the wake of significant aerodynamic upgrades to the C42. These comprised three sets of changes, which can be considered one coordinated update of the car’s airflow. What is significant about them is that they seem to represent a change of philosophy in how the rear ‘coke bottle’ section of bodywork contributes to the car’s aerodynamics.
Alfa Romeo have changed how the coke bottle section works with their Imola upgrades, the rear section of the bodywork now flaring outwards
The ‘coke bottle’ is the section of lower bodywork – at the rear between the floor and engine cover – which swoops dramatically inwards. It has been a standard feature of F1 design since the 1980s. The principle is that the sudden in-sweep creates an air pressure reduction which the oncoming air rushes to fill. This speeds up that airflow along the car’s lower flanks, maximizing its speed as it travels through the gap between the rear wheels and the roof of the diffusers.
The faster it flows, the more downforce is created in principle, as that airflow interacts with that exiting the diffusers from the underfloor. The more accentuated that in-sweep, the greater the pressure drop and the more effective it should be.
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In recent years the coke bottle has tended to be combined with the sidepod undercut to accentuate the effect even further – so that the bodywork sweeps inwards both in plan view and in section. This is how it was on the original Alfa C42, which raced at the first three events of this season.
But for Imola, the undercut was removed from the coke bottle section and the bodywork now comes down to meet the floor much further outboard than before, meaning there is less floor area exposed ahead of the rear tyres. The sidepods themselves are bulkier than before in their lower regions.
The original sidepod (bottom) featured a more extreme coke bottle than the new one (top). This is very much counter to trends prior to the new regulations of this season. Alfa have actually increased the size of the bodywork in this area, finding that it ‘tidies up the flow in front of the rear tyres, improving the flow to the diffuser’.
Alfa claim that this change “tidies up the flow of air in front of the rear tires, improving the flow to the diffuser and the overall aerodynamic efficiency of the package”. In response to the new aero regulations of this year, with the twin venturi tunnels beneath the floor, teams are still in the early stages of finding the optimum trade-off in upper and under-body airflow.
Ferrari have pioneered the extreme use of bluff, bulky sidepods to outwash the airflow as strongly as possible now that the bargeboards – which used to do that job – are no longer permitted.
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With these changes, Alfa seem to be moving towards the Ferrari philosophy and it would seem that more has been found from improved outwash than has been lost to any loss of energy from the coke bottle section.
To accompany this change of sidepod philosophy, Alfa have altered the mini-vanes either side of the central keel at the leading edge of the floor. This will be to give a flow which takes fuller advantage of the new shape of the sidepods. There has also been a small change to the rear brake ducts, better aligning with the revised airflow resulting from the changes around the coke bottle.
Heading to Miami, Alfa Romeo are fifth in the constructors’ standings on 25 points – more than their past two seasons combined, and nearly half of their 2018 total.
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