Saturday, March 2, 2024

Mastering the art of IndyCar strategy

Race strategy in IndyCar is like no other motorsport series on the planet. The variety of tracks, along with the number of tyres and the compact race weekend schedule makes tyre degradation impossible to predict. Teams also need to manage fuel consumption, pit windows and full course yellows – all with smaller teams and more competitive grids than the likes of Formula 1.

Types of track

However, the biggest headache for strategists is the type of track IndyCar races on. There are three types of circuit on the IndyCar calendar:

  • Ovals – short ovals and superspeedways (which are more than two miles long)
  • Road courses – permanent tracks which feature both right and left turns
  • Street courses – made up of closed-off public roads or airport runways

This diverse range of circuits means that lap times can vary from 23 seconds on an oval, to 1 minute 45 seconds on a road course. Consequently, the time lost in the pits relative to the average lap time varies significantly at each track. This not only plays a major role in determining pit windows, but also changes the effect of pitting under a full course yellow. Therefore, the optimum race strategy is completely different depending on whether you are racing at an oval or a road/street course.

A corner of the Indy 500 with cars lining up on it and the grandstands full of fans
Lap times in IndyCar can vary from 23 seconds on an oval to 1min 45s on a road course. CREDIT: IndyCar

Types of tyres

To suit the demands of each circuit, Firestone have had to develop a plethora of different tyre constructions and compounds, giving the engineers lots of tyres to try and figure out.

There are essentially five types of tyres, based on their construction:

  • Street course tyres
  • Road course tyres
  • Indy 500 tyres
  • Superspeedway tyres
  • Short oval tyres

Then there are two compounds, the primary (black) harder compound and the alternate (red) softer compound. On ovals, teams are only allowed to use the primary compound, however, due to the forces generated on ovals, each corner of the car requires a slightly different tyre compound or construction. On street/road courses teams can choose from the primary and alternate compounds as well as one wet tyre.

Close up of a row of primary and alternate IndyCar tyres
Alongside the five different types of tyre construction, there are two compounds; the hard (black) primary compound and the alternate (red) softer compound. CREDIT: IndyCar

‘Firestone does tweak the tyres each year as well,’ highlights David Faustino, Lead Race Engineer at Team Penske. ‘Typically they are trying to tweak the balance between the primary and alternate tyre to get some crossover degradation. But it’s enough of a change which means going into a race weekend, it’s not always obvious how the tyres are going to behave relative to last year.’

Full course yellows

The biggest variable that is outside of the teams’ control is yellow flags and full course yellows. Unlike other series, if a full course yellow comes out during a race, the pit lane closes. A pace car is then released which picks up the race leader and the other cars bunch up behind. Once the pack is formed, the pit lane opens, giving cars the opportunity to pit before the race goes green.

If a car passes the Pit Commitment Line after a yellow, the driver cannot complete a full pitstop (but can repair damage or refuel for two seconds), and has to drive through the pitlane, ending up at the back of the pack. They can then complete a full pitstop when the pit lane opens again.

Several IndyCar cars crashed at a corner apex, with flag panels displaying the Full Course Yellow sign
Full course yellows have a huge impact on race strategy in IndyCar. CREDIT: IndyCar

The strategic difference between ovals and road/street courses

‘A lot of our strategy comes down to how IndyCar handles full course yellows,’ explains Eric Cowdin, Race Engineer at Chip Ganassi Racing. ‘On road and street courses you want to pit towards the front of the pit window, because if a yellow comes out and you haven’t pitted, you have to wait until the pitlane opens again, by which time the pack has completely bunched up.’

‘Typically, cars that have completed a pit cycle before a full course yellow will have a track position advantage,’ highlights Faustino. ‘This is because the leaders will then pit under yellow and will cycle to the back of the cars that have stayed out, assuming they have enough fuel to complete the same number of stops overall. With the point structure in IndyCar you usually see the field split 50/50, so in a 26 car field, if you are the leader and haven’t pitted before a yellow, you could end up 13th, which is a substantial hit,’ Faustino continues. ‘So usually cars will stop early and take the risk of having to fuel save for the rest of the race, in the hope that they will get lucky with a yellow where they can then conserve fuel.’

The IndyCar pitlane with several cars in their pit boxes with mechanics changing the tyres
Unlike other championships, the pit lane closes during a full course yellow. CREDIT: IndyCar

However, on ovals it’s a different story. Pitstops are initially dictated by fuel consumption and a normal pitstop can put a driver two or three laps down compared to the rest of the field. Therefore, by pitting under a full course yellow on an oval, once the pack has bunched up, a driver can complete a pitstop and re-join the track on the same lap – without going several laps down. So, if a yellow falls during a driver’s fuel window, then it is effectively a ‘free’ pitstop.

‘The strategy for ovals is the opposite to road courses. You want to run as long as you dare to try and catch that yellow,’ says Cowdin. ‘But then you also have to consider fuel and tyre degradation. There’s no point staying out 10 laps longer on older tyres if your rival is going considerably faster than you on a new set, because when you do pit, you will come out several places behind them.’

Race strategy software

With full course yellows capable of completely turning a team’s race strategy on its head, engineers need to be alert to this threat and have access to all the necessary information to respond quickly and accurately. However, unlike the live strategy software we see on the screens of Formula 1 and WEC pitwalls, most IndyCar teams use standard timing data alongside their own strategy tools.

However, teams such as Arrow McLaren SP invested in new race strategy software from SBG, called RaceWatch. This is a live prediction tool which synchronises track data such as live timing, race control messages and weather updates with car data including telemetry, GPS and onboard video. The algorithms within RaceWatch then process and analyse this incoming data using statistical models which can predict the probability of an overtake, a driver’s pace during a session and the latest values of tyre degradation.

Screenshot of RaceWatch showing the different fuel windows for each driver
Fuel windows are defined for each strategy prior to the race and show on which laps a driver needs to pit to make it to the end of the race on the desired strategy. CREDIT: SBG

Our aim is to help engineers bring all the data they need into one place,’ highlights Mike Caulfield, Senior Motorsport Product Specialist at SBG and former Strategy Engineer at Mercedes and Haas F1 teams. ‘This avoids them having to manage several spreadsheets and manually move data to populate tools. Instead, RaceWatch automatically picks up all the necessary data streams and updates the models simultaneously,’ Caulfield continues.

‘Strategy software should never tell you what decision to make,’ says Caulfield. ‘In RaceWatch, we try to model the scenarios as best we can and provide all the relevant information in a clear and concise way so that teams can understand the options available to them and the level of risk associated with each. It is then up to the team to decide whether to take that risk or not.’

Screenshot of RaceWatch showing the free air optimisation of three different strategies
Once tyre degradation has been calculated for each compound, strategists will then conduct a clean air optimisation of the race. This assumes there are no other cars on track and defines the optimum strategy based purely on tyre degradation. CREDIT: SBG

> To read the full article on IndyCar race strategy, check out the October 2022 issue

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