Typically, the largest component...
Typically, the largest component in a system is the data logger box. This photo is a 38-channel professional system; however, it is relatively compact and only weighs a few pounds. A weekend racer may have a similar box size but only have one fourth of the cables connecting to the box. This team developed an aluminum plate that is quickly attached to the rollcage with hose clamps. The rubber feet under the box assure a long and trouble-free life for the logger.
If that's not enough to put any chassis man into eternal bliss, these sensors also provide the data for shock absorber velocities. Now, the voodoo and black art of chassis tuning with shocks becomes simple science. Once you know your peak shock velocity and what percentage of each lap is spent in each velocity range, you can identify shock wedge just like spring wedge. With this data, a bad or fading shock becomes very obvious.
Steering Data A data shock can also be mounted horizontally and connected to the steering linkage. Steering position measurements can be used for chassis improvement and driver skill development. With steering position data, "tight" and "loose" go from qualities to quantities. Rather than using the subjective statement, "really tight," you now have a measurement to define the handling. Another fun aspect is not only the maximum steering angle in the corner, but how it got there. Remember, the sensor is measuring the steering position all the way around the racetrack. How the driver turns the steering wheel is very important. This is why some teams call data systems lie detectors, and also why some drivers hate data systems.
Pressure Data Racing sensors are not limited to linear or angular measurements. They can also measure pressure. A common pressure sensor is brake pressure. Because the sensor is measuring pressure all the way around the racetrack, brake usage can be evaluated just like steering. Now you know how much total brake pressure was applied and the location of the car on the racetrack when it was applied. Drivers can evaluate how they got to the peak pressure and how they released that pressure. Sometimes this sensor can be used to find more speed. For instance, a driver claimed to use no brakes, but 75-100 psi of line pressure was measured in the corners. This led to the discovery that the driver was resting his left foot on the brake pedal and didn't realize the g-force was making him drag the brakes.
Throttle Data Another useful sensor, often called a string-pot, is great for throttle position. This sensor is much like a pocket tape measure that rewinds itself. The tiny little cable is attached to your throttle linkage and pulled out of the sensor as you press the throttle. At first glance, this may not be an intriguing sensor, but when used properly, it is one of the best driver development tools available (more on this in the software section of data acquisition systems).
One part of a data acquisition...
One part of a data acquisition system is not located on the race car, but positioned trackside. As the race car passes the beacon, the data logger is signaled that a lap is completed and starts recording the next lap's data. Most systems can provide straightaway and corner segment times for each lap even though a single beacon is used. Typically, a motorcycle battery or regular car battery provides power for larger units such as this one. Lower speeds on short tracks may not require larger beacons, but if you run at Daytona, bigger is better.
Throttle sensors are also valuable for engine developers. When used with rpm sensors, oxygen sensors in the collectors, temperature sensors in the headers, and/or g-force sensors, your data acquisition system becomes a rolling dyno. The big advantage is that you are measuring these items on the racetrack in present conditions. An engine builder's dyno doesn't always reflect the best performance on the track. G-force and banking angles can make a carburetor respond quite differently than on a fixed dyno.
G-Force Data G-force sensors-properly knows as accelerometers-are also common in racing systems. These sensors typically come in a two-axis or three-axis design. A two-axis accelerometer can measure g-force in two directions and is typically mounted to measure lateral g's and fore/aft g's. A three-axis sensor would also include the vertical forces.
Wheel Speed Data Most systems come with wheel speed sensors. Typically, this consists of two parts-a magnet clamped to a wheel hub, and a pickup mounted to the axle flange or front spindle. As the wheel turns, the magnet passes the pickup, and one revolution is signaled. Enter your tire size and you now have vehicle speed at every point on the racetrack. By placing a wheel speed sensor on the front wheel and one on the rear wheel, you now have the ability to measure tire slippage. You can also place the sensors on both rear wheels and see what is happening with your differential. You could even go crazy and place sensors on all four wheels to do a braking analysis.