PAT SYMONDS TECH
Let’s start at the beginning: what is engine mapping and how does it work? In their most simple form, the maps are an array of numbers – in effect a big table of rows and columns, such as you might see on a Microsoft Excel spreadsheet. These tables give values of various parameters, which determine how those parameters may vary as a function of the engine operating conditions.
To give an example, the amount of fuel that is injected into an engine will depend on both the engine speed and the torque that the driver is demanding by means of the position of the throttle pedal. For each discrete value of both these inputs to the map, there will be a specific amount of time for which the fuel injectors need to be open in order to provide just the right amount of fuel that the engine needs.
If you imagine looking at a train timetable, you look along the columns until you see the station you are interested in. You then look down the rows until you nd the time of the next train. The engine maps work in a similar way in that the Engine Control Unit (ECU) will measure the engine speed and index along the table to the correct rpm, while simultaneously measuring the throttle-pedal position and indexing down the table to the relevant position to nd a value that will tell it how long to hold the injectors open.
Of course there are many more maps than this. As well as the amount of fuel injected, you need to determine exactly when in the compression stroke it needs to be injected as well as determining when the spark needs to be ignited. Similarly, the turbo boost required will be determined by yet another map.
Why are they called maps?
If you imagine that in the case above we looked at it in three dimensions, with engine speed representing North/South and throttle position East/West, then the values of injection duration would represent values in the vertical dimension. The effect would be that the data would look like a three-dimensional map of the earth, hence they are called ‘maps’. Are these maps fixed? The base maps are fixed but they may be modified by other inputs. For example, the current Formula 1 engines run close to the point of detonation, or ‘knock’ as it also sometimes known. This is a premature firing of the fuel and air mixture, which can be very destructive and can cause rapid engine failure. The engines are tted with knock sensors which, if they detect any cylinder knocking, can apply an offset from the base-map ignition timing, thereby reducing the propensity to knock. Has it always been like this? No, the technology was not available in the time of the ubiquitous Cosworth DFV F1 engine for example. Even some of the rst-generation turbocharged engines relied on purely mechanical means to control the fuel, ignition and boost. As micro-electronics became more readily available in the early 1980s, so engine control was able to increase in sophistication.
Where are the maps stored?
They are held in the ECU. In the early days they were held in a specific sort of chip called an EEPROM. These were read-only memories, whose contents could be erased and reprogrammed using a pulsed voltage. This was done by removing the chip from the ECU and putting it in a programming device.
In 1986 when I was working for Benetton, we used the BMW turbo engine, which utilised these devices. I bought a programmer and learnt how to re-programme the chips, which were programmed in hexadecimal – a complex number system using base 16 rather than the normal decimal system, which uses base 10.
The late Paul Rosche, who ran the works engines in the Brabham cars, could never understand why we had such good performance and often asked if he could check our chips. I was extremely adept at the sleight of hand needed to remove a chip and substitute it with an ‘approved’ one – which I would then hand to him for checking.
These days the maps are loaded into the car remotely because the ECU is part of the network. This is done by the engine engineers at the circuit who will hold the maps on their computers and download them to the ECU using a specific piece of software. How exactly do the engine maps affect the performance of the engine? The power-unit manufacturer will determine the base map (or calibration as it is often known) by experimentation on a dynamometer, balancing peak performance with the reliability needed for acceptable life. Under the current F1 regulations, they also have to check that the fuel ow does not exceed the regulatory limit. This base calibration will then be used at the circuit, although the engineers working at the track will also be able to make minor changes in response to specific problems or driver requests.
Do you need to use different engine maps for different circuits?
Not really, since the sophistication of the current electronics is such that the maps are suitable for all normal conditions. There may be a few exceptions, for example in Mexico where the
extreme altitude means increased workload for the turbo-compressor, a different turbo speed map may be used.
Can the driver alter the engine maps?
To some extent he can. While there is a base engine map on which the engine may operate, he can also select alternative maps for certain conditions. If we assume that the base map is one that is suitable to use for the entire race then there may be maps loaded that are less aggressive and hence will enhance engine life for use during practice. Equally there will be a special map that he can select just for the hot laps in qualifying, which will push both the engine and the electrical power deployment to the maximum.
Is the power unit the only system that is mapped in this way?
The chassis engineer also has a similar mapping system available to him. These days there are not many maps available, but brake balance and the differential locking are used extensively to optimise handling. The differential mapping is particularly useful as it can recognise corner entry from mid-corner and apply different locking in different parts of the corner. This is particularly useful since the driver can then adjust base maps in response to tyre degradation to keep the car balanced through a stint.
Engine maps determine the amount of fuel that is injected into an engine, depending on the engine speed and torque requested by the driver via the throttle. These maps are updated by engineers on arrival at the circuit