© Vladimir RysBull’s Guide To: Keeping The Car CoolLast time out we looked at keeping the driver cool, but what about all the other vital components in the car? This Bulls’ Guide has the answers…
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We’ll be packing extra laps into the practice programme this weekend to let Max and Checo get a feel for F1’s latest venue, but in the back of the garage, in the Operations Room back in Milton Keynes, and deep within the heart of Sakura, we’ll also have banks of engineers scanning telemetry in the early laps specifically to check we’ve done our sums correctly, and the car isn’t running too hot.
This isn’t something specific to racing in the desert. While the FIA’s forecast, suggesting air temperatures of 33°C on Friday, is on the hot side, we’ve frequently had hotter races at the height of the European summer at Hockenheim and the Hungaroring, even Silverstone last year hit the 30°C mark. Making sure the car has adequate cooling is something the team does every race weekend, albeit with a little more anxiety on a hot weekend and doubly so at a new venue.
Time For The Cool Down© Vladimir Rys
CoolingWhat,AndCoolingHow?
Just as some sharks must keep swimming to breathe, an F1 car has to keep moving to stay cool, drawing air into the radiators and brake ducts to pass over the various surfaces and coolers to keep everything at a suitable operating temperature. This is why fitting fans to the car is the first job the crews do whenever the car stops outside the garage: keeping air flowing into the hot car is job number one at the end of every run because the car has no capacity to cool itself. The brakes are the obvious areas that require cooling when returning to the pit lane.
When in use, the disks may reach spot temperatures of >1000°C but to work at all, they have to be at 500~600°C. This is why you often see marshals extinguishing brake fires on cars that have stopped at the roadside with problems entirely unrelated to the brakes. It isn’t just the brakes, however, the engine and exhaust systems can get very hot also and damage themselves, but more likely, the bodywork cocooning them, if not cooled correctly in the garage. The same is true out on track and is managed by the airflow into and around the car. It needs to operate in a Goldilocks Zone, not too hot, not too cold, but just right.
Not allowing the car to overheat is a simple concept to grasp but the flip side of the coin, not running the car too cold, is a little more involved. While mechanical designers are keen to have as much cooling as they can get, for aerodynamicists, more cooling means more drag, enemy number one, but also a less powerful airstream, enemy number one.
The drag argument is simple: all the things used to scoop-up more of the airflow in turn generate more drag and make the car less aerodynamically efficient. This might be designing a car with a bigger sidepod cross section to get more air into bigger radiators, or temporary measures such as adding extra shoulder louvres (the ‘gills’ some cars appear to have), or simply fitting looser bodywork around the power unit, opening the car up to more airflow.
Off To Cool Down The Car© Vladimir Rys
The rationale regarding airflow is slightly more complex, but the basis is that the airstream flowing over the car is providing an aerodynamic benefit, and syphoning-off air for cooling purposes robs that airflow of energy. The classic example here is in the front brake ducts. Packers within the internals of the duct are configured to split the airflow. Some is diverted to cool the brakes and/or the wheel rim, with the rest being channelled and conditioned to pass over or around the car. More air for cooling means less air for aero and vice versa.
While delivering more cooling than is needed has a negative impact on the aerodynamics of the car, in the case of brake ducts it might also cool the brakes too much. Too much brake cooling is usually a problem confined to circuits with long straights. Somewhere like Baku, for example, is a tough circuit for brakes with plenty of regular hard stops around three-fifths of the lap, requiring a high level of cooling to stop the brakes overheating but the other two-fifths of the circuit is the 2km flat-out section from turn 16 to turn one.
The cooling required to get the car around the rest of the lap suddenly becomes a liability, with too much air wicking temperature away from the pads, such that they struggle to perform in the very heavy braking zone at turn one. There isn’t a magic solution to this, it’s simply a case of finding the best compromise.
The other occasion when cooling becomes difficult is when there isn’t quite so much air available. Air density obviously drops with altitude, and while the loss is noticeable any time we climb up above sea-level, the place where it really hurts is at the Autódromo Hermanos Rodríguez.
High Above Sea Level In Mexico© Vladimir Rys
Mexico City, at 2,200m above sea-level does strange things to an F1 car. Usually, it’s the loss of downforce that makes headlines, and back in the days of the normally aspirated cars the reduction in power also, but it affects cooling just as much. The rule of thumb has air density in Mexico City approximately 78 per cent of what it would be at sea-level, which creates a corresponding reduction in the cooling available to the car.
For powertrains, the question of locating the Goldilocks Zone has to be a little more flexible, since brake cooling is track-specific, but powertrain cooling is weather-dependent. Brakes don’t really care whether it’s 35°C in Singapore or 3.5°C during winter testing in Barcelona because it makes little difference when the operating temperatures are so high.
However, for a power unit, with operating temperatures around 150°C, then a 15°C shift in the ambient temperature, such as you’ll see in the gap between an afternoon practice session and an evening qualifying session this weekend, definitely has an influence on cooling, with the team perhaps fitting tighter bodywork to maximise performance in the evenings.
The one area, however, where the ambient temperature really doesn’t affect the powertrain is the idle time. When the car is fired up but isn’t moving, it’s getting hotter. There’s a hard limit on how long it can stay stationary before the driver has to kill it. In practical terms, the time when there is a performance advantage in having a car that can idle for longer comes when there’s occasion to queue at the end of the pit lane. While it’s often desirable to be first in the queue (when rain is expected in a qualifying session, for example) it’s often a case that the cars with the longest idle time will be able trundle down to the end of the pit lane earlier than their rivals and wait for longer.
Finding The Optimal Idle Time© Vladimir Rys
The cars are, of course, designed to sit at idle on the front of the grid, waiting for everyone to form-up behind them but it can get slightly nervy when there is a delay. This is when the ’go around’ signal is used to complete another formation lap and get some air flowing again.
In the normal course of events, however, the pre-start procedures the team needs to do on the grid and during the formation lap, have a sequence of requirements, not always complementary. The instruction the drivers used to get on the formation lap, back when instruction was allowed, was to ‘warm the brakes, while cooling the engine’. The goal of which is to keep the engine as cool as possible to idle on the grid but have the brakes ready to work with maximum efficiency braking for the first corner. The way to do it is usually to use a high gear at low revs and put in some very hard stops around the formation lap to get the brakes up to temperature.
Before the formation lap, the team will have done as much as possible to make this process straightforward. From the moment the drivers cuts the engine and coasts to the back of the grid, the team starts cooling the car with fans and dry ice. There will, however, be fire-ups on the grid to get fluids circulating and up to temperature too. Depending on the circuit profile and the weather, the crew may also attach brake heaters.
GettingItWrongAndGettingItRight
This weekend, if the team has got its sums right in simulation, the temperatures for the brakes and rims, for oil and water coolers, will be exactly as predicted. If they’re not, then the team will have to take measures to bring them in line. By this point in the year, even though the circuit is new, the car should be a well-enough understood quantity for this not to be an issue.
Fine Line Between Cooling Too Much Or Too Little© Vladimir Rys
It's usually at the start of the season where problems occur. We’ve not been immune to this, with troubled winter testing in the past where bodywork has been catching fire. Elsewhere, we’ve seen other teams frantically throwing damp towels onto the sidepods to prevent scorching whenever the car comes back into the garage, or even, at hot early races in Malaysia or Bahrain, making the ultimate sacrifice of drilling extra holes trackside in their pristine bodywork.
This doesn’t happen very often given how very good simulation tools have become, but what you will see in races are the cars that have pushed their cooling requirements a bit too hard having to drop back in a chase or pull out to the side on the straights to get some clean air, usually with specific instructions to go left or go right, depending on what’s overheating and in which sidepod its coolers are packaged.
This isn’t generally a sign of a failure but rather an indicator of a choice. Somewhere like Singapore, a team will scramble for every hundredth of a second they can find, because a heavy qualifying-bias gives primacy to one-lap pace and accept that, should they become mired in a train of cars, they’ll not be able to follow closely for an extended period of time. At Sepang, where temperatures are similarly hot, the same team might make a different choice because qualifying is not quite so critical.
This weekend it’s difficult to know! Temperatures will be high in the afternoon but not off-the-chart high like they were in Hungary back in July. Street tracks don’t usually give up overtaking opportunities that easily, but this one has three DRS zones, which will help. The track looks very quick but sometimes very quick makes following and thus overtaking difficult. We’ll know more after practice, during which our engineers and our colleagues from Honda will be looking at a whole host of temperature readings very closely indeed.
