Data acquisition systems can be used for several different purposes. We have found that there are two areas where a data acquisition system is extremely useful: to improve the driver’s performance, or to answer questions related to improving the race car’s performance. We have used data acquisition for both purposes, but for most club racers, improving the driver performance is the first priority.
Using data acquisition to improve driver performance
One key to improving driver performance is to have a method of measuring the performance. Lap times are one way we all use, but with a data acquisition system, laps can be broken into smaller segments and the segment times can be examined. A feature I rely on is the ‘split report’ that finds the fastest “rolling lap” in a particular session — because of traffic, yellow flags, etc your fastest lap may not have been from Start/Finish back to S/F, but from Turn 3 back to T3. It also shows the fastest theoretical lap — when I see a good theoretical lap time, it really motivates me to “put it all together” in a good lap — I know I can do it.
But knowing how you did is only one interesting result that can be obtained from a data acquisition system. Corners can be compared to similar corners in the search for opportunities to improve. Once you have established the range your car can operate within (maximum lateral G’s at a given speed), you can identify corners where it might be possible to go faster.
Technique can be examined as well. It’s pretty easy to determine how fast you are shifting gears, whether you are really trail braking into a corner, how smoothly & quickly you roll back onto the throttle, and whether your foot stays planted in those always challenging “no lift” corners.
In addition to comparing your performance to previous sessions at the same track, you have the opportunity to share data with a racing buddy, or have a faster driver turn some quick laps in your car. Comparing your speeds/gears/throttle can really open your eyes into opportunities where you can improve. Once you know where to go faster, it’s not necessarily that easy to “just go faster”, but you will have a goal to work toward.
Much of what has been described can be done without too many sensors/features. Here’s a rundown of sensors commonly used (in what we consider the priority order):
- Wheelspeed sensor provides distance traveled, lap times, and speed at any point on the track, and the software can calculate longitudinal acceleration from velocity changes.
- Lap-timing receiver/beacon. Needed to create “laps” from the speed/distance data.
- Engine RPM is useful for determining what gear is being used, detecting shift times, and verifying that the driver is using the gears correctly to keep the engine in the powerband.
- Lateral Gs can be used to measure the cornering performance, as well as allow the software to draw track maps, and automatically create segments.
- Throttle Position – indicates the driver confidence, or areas that can be improved (perhaps the car needs to be improved to allow more full-throttle application).
- Steering Position – an indicator of driver technique as well as a valuable tool for evaluating handling for the race engineer, or savvy crew chief.
- Brake system pressure – used to examine driver technique with the brake pedal, especially during heel/toe downshifts.
- Other sensors can be used to monitor engine functions (water temp, oil pressure, exhaust gas temp). These are primarily used when the data system also provides dash/alarm functions — and are not always needed if you use conventional gauges.
We’ll talk about other sensors in the “car performance” section below.
I use my data system every time I go onto the track. It’s one of the first things I do after returning from a track session – download the data, look at the split times, examine the data in whatever area I was focusing on for that session. For me it’s part of the “after session tasks”. I am comfortable using the computer and looking at the data. If that task will be performed by someone else, you need to make sure they are available to do it for every session — even if you don’t look at the data right away, capturing it is important.
Keeping track of the car/setup relative to a particular session is also important — good setup notes with what changes were made for each session is always a good idea — when it can be correlated to data it becomes even more useful.
Using data acquisition to improve car performance
As mentioned previously, the second use of data acquisition systems is to work on the race car performance. With accurate data, the race engineer can make changes and determine if the results are helping the performance potential of the car. Of course the driver feedback is very important as well, but when the driver can’t feel the difference, that’s when data systems are the most valuable.
The data that can be used to show change in performance comes from many of the same sensors listed previously:
- Wheelspeed – when taken from the driven wheel, it can reveal traction problems (and indicate when they have been fixed), aerodynamic drag can be determined by using a “coast down test” (more often it is revealed as a “flattening” of the velocity traces at high speeds). Since wheelspeed can produce longitudinal (forward & backward) G force traces, it can be used to measure the effectiveness of braking changes as well.
- Lateral Gs are of course used to judge cornering force. Engineers often examine the average Gs in low-speed (< 70 MPH) turns to evaluate mechanical grip. Aerodynamic downforce should produce a correspondingly higher lateral Gs in high-speed (> 90 MPH) turns.
- Throttle & Steering Position – changes in when the throttle is applied often can be used with steering sensors to provide a clue as to the understeer or oversteer experienced in each turn. By knowing the speed of those turns, the race engineer can modify the handling with camber/springs/shocks/anti-roll bars (for low-speed turns), or downforce changes for high-speed turns.
- Shock position sensors. These can be used simply to determine dynamic ride height (due to aerodynamic downforce effects), as well as provide feedback to the amount of damping provided by the shock/spring combination. At the highest levels of racing, frequency analysis can help determine needed shock changes for a particular track, but most club racers will be happy to just learn how much downforce is being generated, and the relationship of front-to-rear downforce.
When searching for downforce, sometimes engineers want to understand the pressure changes on the bodywork, and pressure sensors allow this information to be captured. This can help optimize diffusers, spoilers and other aerodynamic devices.
Other questions that race engineers often have can be answered:
- What is the speed range in each corner and what’s the maximum speed on the straights — this allows optimum gearing to be selected.
- What camber, tire pressure, and tire compound produce the maximum lateral grip for a given track/weather condition.
- Engine builders often want to know where in the RPM range an engine spends most of its time per lap. If engine sensors are logged, then oil pressure, water temperature, etc can be examined and changes made if they are not operating with the ideal range. Changes might be as simple as taping a radiator, or selecting a different oil viscosity.
- If EGT (Exhaust Gas Temperature) probes are attached, the air-fuel mixture can be modified based on results (if too hot, motor is running lean, and larger main jets or smaller air correctors can be installed).
Now a club racer typically doesn’t look at all this data every time. But they may pick one area to focus on, and capture data to help understand what is happening. It’s important to understand that data acquisition systems provide the answer to questions (Is the car balanced at the exit of T3?), but do not necessarily indicate what needs to change to improve the performance.