INSIGHTS

  • THE POWER OF HEAT

Report

6 April 2018

If there’s one thing people working in Formula 1 can rarely complain about, it’s the weather. As a sport, F1 chases the sun, racing in venues where it tends to be warm. Sometimes very warm. But then there are the occasions when warm turns to hot, and starts becoming an influence on performance.

An F1 power unit runs hot enough as it is, without a further push from the ambient temperature.

Look at a weather forecast for this weekend’s Bahrain Grand Prix and you will see day after day at 30C or higher, and even the overnight lows are in the mid-20s. So just what happens to the power unit when things start to hot up?

SATOSHI NAKAMURA | PRINCIPLE ENGINEER, HONDA F1

Normally when the atmospheric temperature goes up it means the water temperature, oil temperature and the air intake temperatures also go up.

“Especially the plenum temperature - the induction temperature for the engine - that goes up, and this has a big impact on the performance and reliability side.

“High temperatures can lead to knocking - when there is irregular timing of the combustion - so that means we have to turn the performance down to avoid it. We are always being very careful with high temperatures.

Knocking is bad for both performance and reliability because from a damage point of view it can have a big effect.”

30 degrees is the magic number when temperatures start to be monitored even more closely, but it’s not just when the mercury is rising that the power unit notices a difference.

“The best is 20 or 21 degrees,” Nakamura says. “When it is much lower temperatures we don’t have specific engine mapping because you don’t expect it. So from a performance point of view that means it’s not so good as well. If we had mapping for it then it would still increase the performance.

“When it gets hot, the exhaust pipe and the turbine are likely to be the biggest issue. We are always monitoring the temperature using sensors.”

And by hot, Nakamura means seriously hot. The MGU-H limits how much heat energy is wasted as it converts the heat from the exhaust gases back into power, but even so the exhaust temperature can reach 1000 degrees centigrade. For comparison, that’s the same temperature as the brakes are capable of reaching when they glow red hot under maximum braking.

The power unit is designed to run at higher temperatures, with the water temperature typically between 120-130C. The water system is pressurised to allow it to reach these higher temperatures, whereas your typical road car will be running some 33% lower.

While air temperature has an impact, the power unit also needs to be protected against the impact of the track itself.

“For starters, the track temperature means the air temperature is also high!” Nakamura says. “Heat comes from below the power unit so you have to protect against that with heat shielding, but many parts have shielding on them.

“Especially the exhaust pipe has a lot of heat shielding, because the exhaust pipe is very important for the energy recovery from the MGU-H and turbine.”

Clearly overheating is something that all power unit manufacturers are keen to guard against, with drivers often told to find clean air - away from the wake of the car in front - to aid cooling. But what happens when things start to get too hot? Well, quite simply, the power unit reacts.

“For example if the exhaust temperature goes higher and goes above the limit, the fuel flow rate goes down automatically. It’s a failsafe action, and then with less fuel you get less power and you go slower.

“If the exhaust overheated, then the wastegate valve could get broken or the turbine blades could be operating at over 1000 degrees and that can do big damage to the turbine blades. So we have to keep the temperatures low.”

Telling the driver to move out of the dirty air of another car is one approach when on track, but before the car leaves the garage there are measures that can be taken to counteract against high temperatures.

SATOSHI NAKAMURA | PRINCIPLE ENGINEER, HONDA F1

“To keep the power unit cool we open up bodywork and cooling inlets. The side pods and the exit ducts are important parts, and also the radiator size.”

“You open up the exit ducts because you need to get the heat out more quickly, but if you use the big ducts then the aero efficiency goes down. So we are always trying to balance performance with the cooling effect, it’s a constant trade-off.”

That trade-off is made in partnership with Toro Rosso in order to try and minimise any aerodynamic impact. Cooling specifications are built into the car’s design, with the airflow being directed into ducts.

When the car comes to a halt after returning to the pits, there is no natural airflow to cool the power unit, and that’s when you see the pit crew spring into action.

“We use dry ice to cool the PU in the pits and the fan size this year is much bigger than last year. Toro Rosso has a good facility so we have more cooling this year.”

Of course, finding out that the power unit is running hot when it’s in the car can reduce vital track time, so tests take place back at Sakura to gather data on how it will perform.

“When we have the power unit on the dyno we make the area hotter,” Nakamura reveals. “So when we are testing on the dyno we change the temperature by doing things like turning off the air conditioning.

“Once we get some data and then we get to know at which point we can set the limit, but we don’t actually run on the dyno until the component breaks.”

If safeguarding against heat wasn’t enough of a task, Bahrain poses another challenge: Sand.

With the Bahrain International Circuit based in an exposed area some 20 miles south of the capital Manama, wind can lead to sand blowing across the track, and those particles are tough to stop.

“I’m not so concerned about Bahrain’s temperature, I’m more concerned about the sand,” Nakamura admits. “Bahrain is a desert, so that has an impact as well.

“For example if sand got through to a bearing and a bearing was broken… There’s nothing you can do about stopping sand.”

While such a scenario is unlikely, sand may affect the efficiency of intake if too much gets stuck in the air filter, which can lead to the need to change the air filter more frequently than normal.

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