Track Testing

Track testing has the potential to offer the most accurate and inaccurate aerodynamic testing method simultaneously. Airflows are completely accurate, but the ability to measure them is very limited, hence knowledge of them is poor. 

It is the only technique that uses the actual racing car in real world conditions. All factors that affect aero performance can come into play, from car surface geometry, thermal effects, ground effects, tyre effects, engine intake and exhaust flows etc.  Unfortunately, they tend not to come into play in a controlled manner, hence it can be very difficult to separate causes from effects.  In particular, the weather will play a part, with gusting winds the greatest headache.

Forces acting on the car normal to the ground (down force or lift) tend to be measured by strain gauges fitted to the suspension.  Resolution can be poor and it can be difficult to calculate out the inertial effects of the car's motion.
Forces acting on the car in the direction of motion ( drag ) can be measured via torque sensors in the drive-train or by using 'coast-down' techniques.  The torque measuring technique is preferable, but resolution is again poor.

Teams try to control some of the influences by testing at specialised aero testing tracks.  These typically feature very long straight sections and are located in regions where the weather tends to be more stable.  These facilities will improve the resolution of the data acquired, but data quality, and hence the conclusions drawn, can still be unreliable.

In terms of cost, this can be a very expensive option.  A team of engineers and technicians may be required to run the car depending on it's complexity.  These people will need to travel to the venue,  and will need food and accommodation for the duration of the test.  Equipment will need transporting to the venue and back again. Running the car and engine will eat into the available life of each and consumables (such as tyres and fuel) will need supplying. The test car itself is essentially 'free', though the cost of  producing full scale test components that are able to survive the rigours of life on a race car may be very significant.  Fitting suitable instrumentation to the test car can also be expensive and time consuming.

Obviously, this development technique also relies on the availability of a test car, hence it is of no use to 'clean sheet of paper' design exercises.

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