Traditionally Formula One car performance progresses from one season to the next primarily through a combination of tyre, engine and aerodynamic development. In 2008 the cars are running on the same Bridgestone control tyre as before and the engines are essentially unchanged. In fact, if anything there has been a loss from the powertrain. The introduction of a ‘spec’ Single Electronic Control Unit (SECU) to run it has not affected the small gain that all the major players have made in recent years through seamless gearshift systems but it has cost traction control and engine braking assist. However, the tiny loss of lap time that represents will be dwarfed by the gains made over the winter by the aerodynamicists. The 2008 cars will be faster, even if they are no more powerful and are more challenging to drive.

Driving is more challenging in 2008 due to reduced engine control

THE PACKAGE
Chassis technology on the mechanical side (monocoque, dampers, brakes, etc) is these days about incremental gains. Readers interested in the whole car environment will find detailed information in our sister publication F1 race technology Volume 2 out this April. From the lap time perspective the highly significant factors are that the parameters within which the aerodynamicists work are hardly changed by the rules (only a slight increase in the height of cockpit sides) while the needs of the control tyre are now more fully understood.

The recent tyre war provided sufficient scope through tyre development that Renault, having handicapped itself with a heavy engine for 2004, was able to successfully pursue a rearward weight bias whereas other Michelin runners went in the other direction to just as good effect. The control tyre has now pushed everyone to a forward weight bias, with somewhere in the region of 44-48% of total weight on the front tyres and an appropriate aero split. From the point of view of aero the forward bias has forced Renault away from its traditional V-keel approach to front suspension mounting, to join the rest in a zero-keel design. At the same time there has been a trend to longer wheelbase dimensions, primarily to provide more scope for the aerodynamicists.

The contemporary Formula One car carries in excess of 50 kg ballast but the FIA has frowned upon the practice of putting a significant amount in the nose. As a consequence there is pressure to look to means to alter the car’s architecture so as to move weight forward.

There was the same pressure in the late nineties, following the introduction of grooved tyres. At that time the Stewart Ford team and its engine supplier Cosworth were ahead of the game. Stewart moved the engine oil tank from its usual location in the bellhousing to the front of the engine, so that it nestled in a recess in the back of the monocoque’s fuel tank area (nowadays the universal solution). Stewart also developed a lightweight transmission case using carbonfibre technology (others have since found other materials just as effective) while Cosworth removed cylinder liners from its engine to help make its V10 more compact and lighter.

Engine Developments Ltd used screw in liners to produce the first sub-100 kg Formula One V10 then Cosworth showed the way forward with its linerless approach. However, with the switch from 3.0 litre V10 to 2.4 litre V8 for 2006 the FIA bucked the trend to ever smaller, lighter engines. The size and weight of the V8 package is effectively set by the rules, through a specified bore centre spacing (106.5 mm), a minimum crank height (58 mm), a minimum weight (95 kg), a minimum centre of gravity height (165 mm) and so forth.

So the potential to manipulate engine architecture to packaging gain has gone. Nevertheless, in an effort to move weight forwards in mid 2007 McLaren introduced a lighter gearbox while this year it moves to a longer wheelbase, moving the engine forward. Team boss Martin Whitmarsh remarks: “Although we achieved virtually the weight distribution we were seeking in 2007, that was achieved … by putting ballast at the extremes of the vehicle. The fundamental (un-ballasted) weight distribution of the 2008 McLaren… has been moved forward.”

WATER & OIL SYSTEMS
The idling ability of McLaren’s 2007 specification Mercedes V8 became evident in Malaysia, at the first hot race of the season. Here the McLaren-Mercedes was able to wait on the sun baked pit road, engine running for minutes at an end without overheating. This gave the team scope to put its cars at the head of the lane early enough to ensure they led out onto the circuit for the pole session, gaining valuable track position.

Clearly since the car wasn’t moving this had nothing to do with airflow through its radiators. Rather it was evidence that Mercedes Benz High Performance Engines (MBHPE) hadn’t compromised on the quantity of coolant in its engine and had instigated a clever strategy to run the engine on idle as a four cylinder. Some years before Cosworth had introduced the concept of separate cooling systems for the heads and block to reflect their different requirements while the concept of the idling strategy is to fire four rather than eight cylinders on each engine cycle, alternating the quartet that are fired. This halves the amount of thermal energy that has to be dissipated; less goes into the coolant (the flow of which through the radiators can be speeded up to further assist) and radiation becomes adequate to reject the heat.

2008 McLaren-Mercedes won out of the box

Some while later Ferrari followed this idling strategy but first it had to sort out its 2007 car’s cooling at speed. The heat of Malaysia led Ferrari to compromise its bodywork just to get sufficient cooling for the engine and yet it still had to cut engine revs in the race. This led to revised aerodynamics for the 2007 Ferrari, providing a better compromise between car performance and the cooling requirements of the powertrain, which embrace engine coolant and oil, gearbox lubricant and the fluid for the hydraulic systems that help control them.

Since the Formula One engine was forced to run two consecutive race meetings there has been a significant increase in the cooling provided to each piston by means of oil spray. Multiple oil jets nowadays spray the underside of each piston. Mecachrome developed a steel piston that had no weight disadvantage and reduced the oil cooling requirement but the rules have been changed to mandate aluminium alloy. On the face of it there is little difference in cooling requirement between the six current V8 engines, all of which have comparable power output.

It is routine these days to pressurise the coolant system. It is at normal atmospheric pressure (1 bar at sea level) that water boils at 100 degrees centigrade – pressurising it pushes up the boiling point, so that less cooling is required for the engine, to the benefit of car aerodynamics. Pressurising the coolant also means that steam bubbles forming inside the engine are beneficially smaller. Before the FIA mandated a limit of 4.75 bar absolute at the header tank pressure relief valve, systems were pushed towards 6 bar, allowing coolant temperatures in the region of 140 degrees.

2008 Mercedes V8: fundamentally unchanged from the year before

On the car side we find the Northampton, UK based NAR Group, which specialises in the manufacture of automotive radiators currently developing new cooling technology for an undisclosed Formula One team. Conventionally Formula One cars use bar and plate type oil radiators since the alternative tube and fin type does not lend itself to the complex 3D shapes demanded of contemporary chassis designs. However, NAR is now working to develop ‘wave fin’ technology to attain a shaped tube and fin oil radiator with notably high performance.

In this type of aluminium oil/air heat exchanger, if the oil is passing horizontally through tubes, the airflow passes also horizontally but at right angles to the fluid flow, travelling through the gaps left by fins that are sandwiched by the tubes. The fins are made of wafer-thin aluminium that is folded and concertinered to form a wsection. The fins are attached along each fold to the adjacent tube to maximise the transfer of heat from the oil to the airflow. Normally the fins provide a straight through-passage for the air whereas the wave fin as its name suggests creates a snaking through route. This design of fin lends itself to be formed into complex 3D shapes, unlike the regular straight fin.

Compared to a conventional straight fin the wave fin can be thinner (0.078 mm versus 0.12 mm) and for a given air pressure change across the radiator it exposes a greater surface area to the airflow. In fact, tests have shown that its lower resistance is such that it can provide 27 fins per inch for the same pressure change as is created by 21 straight fins. It can be lighter for a given heat transfer requirement, partly because it holds its shape better under the aerodynamic forces experienced at speed.

In addition to this NAR has improved the design of the ‘turbulator’ housed inside each oil passage, which encourages the fluid to transfer heat to the tube wall and thence to the fins. This further improves the efficiency of the wave fin production. The key to these developments is the exploitation by NAR of ‘Controlled Atmosphere Braising’, a noncorrosive flux braising process developed by Alcan. NAR now has in house a specialist furnace that provides the vacuum purging required by the CAB process. The company believes that for a given Formula One oil radiator requirement its new wave fin production can outperform a bar and plate design.

STORY CONTINUES IN ISSUE 29 OF RACE ENGINE TECHNOLOGY. BUY YOUR COPY AT WWW.HIGHPOWERMEDIA.COM

This article from Race Engine Technology magazine was published by permission.