FIRST PRINCIPLES DATABYTES A frame of reference
Understanding key comparison factors in a given data outing using common details, such as time and distance
Databytes gives insights to help you improve your data analysis skills each month as Cosworth’s electronics engineers share tips and tweaks learned from years of experience with data systems. Plus we test your skills with a teaser each month.
To allow you to view the images at a larger size they can now be found at www.
racecar-engineering.com/ databytes
W
e all know that perspective can change how we
interpret what
we see. Looking at an aeroplane from a moving car can make it seem almost at standstill, and the sound of an ambulance siren changes depending on whether it’s moving towards or away from the listener. The same applies to the
interpretation of racecar data. Different reference points can
have a significant effect on how the data is interpreted and whether we can find what we are looking for. If the correct scale and reference points are not used, it is possible to get false information which in turn can mean a wrong decision in the race. For example, if an oil pressure
alarm comes up, it is necessary to know what the qualifiers for that alarm are. Obviously the pressure itself has dropped below the normal operating value, but the oil pressure is also relative to the
“Producing data relative to distance makes it possible to determine exactly where a certain event occurred”
engine speed. It may be that the oil pressure warning is of low importance as the engine speed is also very low. Therefore the oil pump might not be at full capacity. A good way to look at information that changes with another factor is to use an X-Y plot. This clearly highlights when there is a cause for concern. Below is an oil pressure vs engine speed X-Y plot and it’s clear that at high engine speed the oil pressure is normal, but at lower engine speed it drops. This is not a cause for concern. If the oil pressure starts to drop at the far right end of the graph it is time to conduct further investigations.
Time or Distance A key element of data analysis programs is the ability to reference not only to distance, but also to time. Producing data relative to distance makes it possible to determine exactly where on the circuit a certain event occurred, and if it’s possible to create a basic track map in the software then this becomes even easier to visualise. Generally when two laps are
Figure 1 Oil pressure plotted against engine speed
being compared the reference should be the distance travelled. This makes it possible to see, for example, whether one driver is braking earlier or later than another. Over the page there is an example of the difference between using time and distance for driver comparison. Looking at the brake pressure it is clear that if the time domain is selected the information seen does not give a correct picture of what actually took place. Using time, it seems that on the green lap the driver applied the brakes earlier than on the red, but
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