KERS in F1, a ruleset for innovation

By on

For most of us when the FIA technical regulations for F1 were released midway through 2008 we not only stared in mock horror at the drastic revolutions that were about to happen to the cars themselves aerodynamically which became the heart and soul of formula 1 as we knew it, but we also took note of a new section in the regulation relating to the Kinetic Energy Recovery System.

During the latter half of 2008, it was one of the most talked about items, and also the most anticipated. For most of us seeing the photos of the first prototypes of the Ferrari’s and the Mclaren’s during the 08/09 winter testing period with asymmetric bodywork, we surely wondered if the gloss of the sport was going to be tarnished. Thankfully the teams managed to preserve the sheer beauty of the cars and the sport with evolution and revision of KERS systems in the short time between opening testing and the first race in Melbourne at Albert Park, while also staying true to being functional systems.

What we will discuss here is why KERS was an initial failure to the spectators of the sport and why the technology has failed to deliver the promised 2-4 tenth of a second per lap that the simulations were expecting to deliver. We’ll cover the differences in potential technologies that have been developed and deployed, where it is most useful, what the teams would have to have considered and subsequently the lack of delivery on the track in the early days, the tactics to use KERS, and then tie this all in with the technical regulation set down by the FIA, and possible future technologies that we will soon see in 2014.

For those that aren’t aware, KERS is the Kinetic Energy Recovery System which harnesses car energy under braking and then releases it via driver control under acceleration. Considering that KERS can only deliver a total of 400kJ of energy at a maximum rate of 60kW the minimal time that KERS can be used per lap is 6.67 seconds.

Mercedes KERS package of 2011

The following are the technical regulations set down by the FIA relating to KERS in 2009.

5.1.3 Crankshaft rotational speed must not exceed 18,000rpm

5.2 Other means of propulsion 5.2.1 The use of any device, other than the 2.4 litre, four stroke engine described in 5.1 above and one KERS, to power
the car, is not permitted.
5.2.2 With the exception of one fully charged KERS, the total amount of recoverable energy stored on the car
must not exceed 300kJ. Any which may be recovered at a rate greater than 2kW must not exceed 20kJ.
5.2.3 The maximum power, in or out, of any KERS must not exceed 60kW.
Energy released from the KERS may not exceed 400kJ in any one lap.
Measurements will be taken at the connection to the rear wheel drivetrain.
5.2.4 The amount of stored energy in any KERS may not be increased whilst the car is stationary during a race pit stop.
Release of power from any such system must remain under the complete control of the driver at all times
the car is on the track.
5.2.5 Cars must be fitted with homologated sensors which provide all necessary signals to the SDR in order to verify
the requirements above are being respected.

8.2 Control electronics 8.2.1 All components of the engine, gearbox, clutch, differential and KERS in addition to all associated actuators must
be controlled by an Electronic Control Unit (ECU) which has been manufactured by an FIA
designated supplier to a specification determined by the FIA.

9.9 Kinetic Energy Recovery System 9.9.1 The KERS must connect at any point in the rear wheel drivetrain before the differential.
9.9.2 The system will be considered shut down when all energy is contained within the KERS modules and no high
voltage is present on any external or accessible part of any KERS module.
The shutdown process must take no longer than two seconds from activation.
2009 F1 Technical Regulations 31 of 67 17 March 2009
9.9.3 It must be possible to shut down the KERS via the following means :
- the switch required by Article 14.2.1 ;
- the switches required by Article 14.2.2 ;
- the switch or button required by Article 9.4.
9.9.4 The KERS must shut down when the ECU required by Article 8.2 initiates an anti-stall engine shut off.
9.9.5 All cars must be fitted with a KERS status light which:
- is in working order throughout the Event even if the main hydraulic, pneumatic or electrical systems
on the car have failed ;
- is located in the same general location s the light required by Article 8.10 ;
- is green only when the system is shut down ;
- remains powered for at least 15 minutes if the car comes to rest with its engine stopped ;
- is marked with a “HIGH VOLTAGE” symbol.

At a glance we can see a great deal of potential for KERS from 2009 and we can also see the justification for all the initial development by the teams such as Renault (Currently Lotus), Ferrari, Mclaren, Williams and BMW (Now Sauber).

But firstly let’s ask a few basic questions. Will KERS make the car go faster? Will it quicken the standard lap time? Will the benefits outweigh all the inevitable drawbacks that come with integrating a new piece of technology, into a previously well-known and understood racing machine? Before we answer any of these questions we must first understand a few facts and principles, and how KERS integrates into the entire drive system.

Rotational Power (W, Watts) is the product of rotational speed (w, radians/sec) x by the rotational torque (T, Nm). (P = w x T), in the same way as power is the product of Linear Velocity (v, m/s) x Force (N). To convert to Radians, take Engine RPM then multiply this ((2 x pi) / 60)

We can see why there was such a drastic power reduction after 2005 when engine volume, and engine rev limits were imposed to 19,000 rpm, and currently 18,000 rpm and soon to 15,000 Rpm (2014), from upwards of 20,000 rpm, thus making total power, torque dependent.

Rotational Torque (T, Nm) is the product of Rotational Mass (J, Inertia) x (Angular Acceleration, Change in Velocity over the Change in Time, dw/dt). (T = J x (dw/dt) or (F x Radius)), in the same way as Linear Force is the product of Mass (Kg) x (Acceleration m/s^2). The F x Radius will become
more important later.

Neglecting mechanical losses we will treat gearboxes and differentials to simply reduce speed according to the gearing ratio and to multiply torque by the same factor. As you will see, if you take; P = w x T and then pass this through a gearbox with a reduction ratio of 2:1 you will end up with; P = (w/2) x (T x 2), whereby you will be moving at half the speed, but able to push more inertia / accelerate quicker.

We can also appreciate that with a fixed amount of power, the lower the revs of the motor, the greater the torque. If you doubt this take a look at a semi-trailer and compare the difference to a fully loaded rig to an empty one. An empty one will even give a standard car a run for its money, but the same car will never be able to haul as much freight!

Ultimately the power at the output will be the same as the power into the gearbox (neglecting mechanical losses). With gearing in the final drive an arbitrary constant and with 7 forward gears to choose from we can now understand clearly how the torque is multiplied far more in lower gears than in higher gears where rotational speed is much more important, but still enough torque is required to offer enough forward drive, to balance the rearward drag of the car.

At the end of the day regardless of the design of the power train, between any teams, a 2.4 Litre V8 producing approximately 740HP blasting down the front straight of Monza at ~330Km/h each team regardless of any gearing or differential combination will typically end up with the same power combination of speed and torque at the rear wheels, especially considering that the dimensions of the tyres are fixed according to the technical regulations. From here we can now start to analyze KERS against the regulations set down by the FIA as well as evaluating it honestly for what it truly is, and what it offers.

This article is the first in a series where we look at the KERS systems in use from 2009 to 2013. Next we will look at what KERS has to offer to enhance the performance of a Formula One car Text by Richard Ronc, Ronc Industries Image courtesy of Mercedes HPE