The Bahrain Grand Prix is one of the few twilight races on the Formula One calendar, so what can teams learn from the two daytime practice sessions?
INSIGHT: Daylight vs Twilight - What Can F1 Teams Learn?
Racing in Bahrain throws up a rare and rather unique challenge. Alongside Singapore and Abu Dhabi, they are the only F1 events that run sessions both in daylight and twilight - which present teams and drivers with very different track conditions.
It makes preparing for these races trickier than most. In Bahrain, first practice and third practice take place in bright sunshine and with the backdrop of gorgeous blue skies. But, second practice, Qualifying and the race are completed as the sun sets and day turns to night, lit up by bright floodlights.
Therefore, what F1 teams can learn and gather in FP1 and FP3 is somewhat limited, as the conditions and environment is so different to the one they'll be qualifying and racing in. But, teams make the most of the track time, because there's still some knowledge to be gained.
This is especially true for Bahrain, with the race being the second round of the 2018 F1 season. The daylight sessions are the first time the new cars have been run in very warm conditions, so it puts cooling specifications to the test.
Seeing how a car's cooling package holds up to the searing heat of Bahrain is a crucial lesson for the season ahead, with races such as Hungary, France and Brazil also set to feature very high air and track temperatures.
It's also a good opportunity for teams to see how the new range of Pirelli tyres behave in such a warm climate. Bahrain's weather is very different to the cold conditions of pre-season testing in Barcelona, so having a hot session on a consistent track is handy.
Therefore, teams treat FP1 and FP3 in Bahrain as a test session for later in the year, completing experiments and trial runs. It usually throws up a pretty mixed-up order on the leaderboard as a result, with everyone being focused on different things.
While conditions are unrepresentative, the third and final practice session can still be used to check any changes that have happened to the car overnight, the systems, Power Unit, fuel consumption and more. It's not a completely wasted hour, but it isn't particularly useful for setting up the car and finding the right balance.
At last year's Bahrain GP, track temperatures dropped from over 47 degrees in FP1 to 35 degrees in FP2. The following day, FP3 took place in 39-degree heat, but this figure fell to 30 degrees for Qualifying and it was the same for the race on Sunday too.
That's a drop of around 10 degrees (or more) between the daylight sessions and the twilight sessions. This can not only alter the balance of the car, but it also changes how the tyre is working, because it can move the Pirelli rubber out of its operating window.
Cooling and the brakes are also impacted by this temperature shift. Some teams may even use different cooling specifications in the daylight sessions, before switching over for the twilight running. It's helpful in some ways, to find out how the cooling handles the heat, but this alters the aerodynamics of the car.
Therefore, because of how the conditions impact the cars and the tyres, it's very tricky for teams and drivers to work on car set-up and balance in these two sessions. Things change so drastically for the sessions that really matter, so FP2 is the only real chance to hone the set-up and find the sweet spot.
All of this doesn't even take into account the track evolution in Bahrain, which is constantly changing from session to session. Due to the Bahrain International Circuit's desert location, sand is often blown onto the track. This makes things even trickier and means that while the temperatures may become cooler as day turns to night, the track itself becomes faster as it's cleaned up.
The drastic dip in temperatures and the evolving conditions of the Bahrain GP weekend aren't experienced all that often. Abu Dhabi runs a similar schedule, but as it's later in the season teams have already gathered the information they need. FP1 and FP3 in Singapore are run in the day, but due to its more humid climate, the temperature changes aren't quite so dramatic.
Bahrain's always a challenging weekend for F1 teams, but they just have to try and make the most of the track time they have. While the daylight sessions aren't as useful as the twilight ones, there's something to learn every time the cars hit the track.