Data Logging

What is it, how does it work?

All the cars used by Itratec Motorsport are fitted with data loggers. A data logger is an electronic device which measures the output from various sensors hundreds of times a second. This information is downloaded onto a computer at the end of the run for analysis. In International motorsport some teams are able to relay the information from the car back to to pit crew for analysis during the race.

Most data loggers record engine revs and speed. Just these two sensors can provide a wealth of infomation, particularly if two driver's recordings are compared. Drivers within a team often agree to swap data, as although another driver may benefit from your data, you will also learn from theirs.

Speed and rev data can be used to compare braking points, gear selection, and identify exactly where time is being lost. Reading the data is quite an art, as on first inspection traces can appear very similar. However, close inspection will show minor differences which can have a dramatic effect on lap times. For example, going into a corner too fast will usually lead to a slow exit. A slow exit, say 75mph rather than 78mph, will result in lost time for the entire length of the following straight, which could amount to half a second or more.

Additional sensors are often also added. G force sensors can measure lateral forces (side to side) or longtitudinal forces (acceleration and braking). The output from lateral G sensors can be combined with speed and distance data to automatically draw a map of a circuit to help with the analysis.

Other sensors include:

Fuel pressure

These are a selection of the sensors, although anything which moves, or has pressure can be measured.

Example output

The example above shows two laps of Snetterton. The lap shown by the green trace took 1min 10.52 seconds, the lap shown by the white trace took 1min 10.50 seconds. The pink line rises or falls as the green lap gains or loses time against the white lap.

Looking simply at the lap times, the two laps appear very similar (only 2 hundredths of a second difference). However, the driven laps were quite different.

The white car came out of the corner before the start quicker, and hence at the start of the graph makes up time along the first straight. By the first corner he is 0.1 secs ahead. However, a 'moment' in the first corner loses him 0.05 secs. He benefits very slightly in the next very slow corner, but the length of the next straight multiplies this so by the time they hit the brakes at the mid point of the lap the white car is 0.2 secs ahead.

White brakes slightly earlier at the end of the straight losing 0.05 secs, although green locks the wheels under braking regaining white 0.04 secs.

Green then drives the final section much better, regaining 0.40 secs, although he loses 0.2 secs coming out of the final corner and back up the straight to the start line.

If a driver were to learn from the other, and correct his slower corners he could easily reduce his lap time by 0.5secs. In a twenty lap race that gives him a 10 second advantage.

This information can also be given in numerical tabular form, splitting the circuit into sections.