Data acquisition can be used for testing, but it's not accepted for competition in many U.
Speed costs. How fast do you want to go? Or so the saying goes. In that same mindset, many racers complain about other racers beating them with cubic dollars. Granted, money has a great impact on racing, but not always.
Occasionally, something very affordable comes along that makes everybody stand up and say, "Wow!" Imagine sitting in the pits (during the late '50s) when the first car rolled through the back gate with a great big wing on top. That type of shock factor has happened again. This time, it's data acquisition.
In professional racing, data acquisition is very common and has been in use for roughly 15 years. Now, it's spreading to all levels of racing and for a very good reason. Few items have the incredibly huge performance potential of data acquisition. As such, the number of data acquisition users and suppliers is growing.
Contrary to what you might imagine, data systems are affordable, relatively simple, and easy to operate. Don't be scared just because they are electronic recorders. If you can operate a telephone answering machine, then buckle up, because your race car is about to get a whole lot faster.
Wheel position sensors are commonly called data shocks. They are compact, lightweight, and
Affordability When it comes to something new and different, the first thought is always about cost. Actually, like most electronic gadgets, prices for data acquisition have migrated downward and become surprisingly affordable.
Peter Kelly of Competition Data Systems states, "System costs are incremental, but [each] value is huge. A lot of it depends on what you want to measure and record." Prices have been coming down on all systems, and pro systems may come down a little more. Many subparts are manufactured by third parties, which limits how much the prices can decrease.
"Prices only go up when a new technology comes to market," says Scot Elkins of Pi Research. "Typically, data acquisition is the last thing racers think about, but any system can be a huge advantage." Whether it is a basic system that just records rpm, or a full-blown pro system, the performance potential is huge.
Just as a Nextel Cup tire costs more than a Hobby Stock tire, the same is true for data acquisition systems. Professional-level circle track systems can cost $20,000 or more; however, for around $5,000, you can get an ASA-level system from Competition Data Systems. Even more affordable are systems by Comp Cams for $3,600 or Performance Trends for roughly $3,500.
Pressure sensors can be plumbed into brake lines, oil lines, or fuel lines. This brake lin
You may think this is a lot of money, but you could easily spend it on a motor. Remember, there's added value from a data system. If you change classes, you can use it on the new race car (which you can't always do with a motor). You might even think of the system as an investment and rent it to racers in other classes. You definitely can't do that with a motor.
Although price is typically used as the reason to outlaw data systems, it's not fair legislation. To quote Elkins, "If a racer has enough money, he is going to get a 50-foot trailer rather than a 20-foot trailer; you just can't control spending." However, if by using a data system, the midpack racer learns what the weekly winner knows (and then becomes a front-runner), it improves the show.
Anybody who wants to win or is serious about racing needs to own a data acquisition system. A good rule of thumb for a purchase might be to look at how much you spend on an engine. An equal amount of money, or only half as much, toward data acquisition is going to be a wise investment. In fact, for what you spend on a Super Late Model engine, you could buy a NASCAR Cup-level system.
When selecting systems, Kelly states, "Deal with an established company. Support, reputation, and experience are very important." If you need customer support, a U.S. company is likely to be better than a company on the other side of the world in a different time zone. Just like any other part of racing, it is helpful to look around and ask others what they have found.
Throttle position sensors can be mounted in the engine bay or in the driver's cockpit. TV
Data Acquisition Basics Relax-this is not going to be a lesson on how to build an atomic clock. But, just as you need to understand engine basics before you can set the timing, it is necessary to understand data system basics to see the incredible performance potential.
Data acquisition systems are not as complicated as you might expect. The basic concept is very simple and easy to understand. A data system has three basic functions: 1. sense or measure; 2. save; 3. replay.
Chances are you use machines that do this every day, but never thought to apply it to your racing. For example, an old-fashioned phone answering machine can be thought of as a data acquisition system. A microphone (sensor) is used to measure a voice message. The electric signal from the microphone is saved on a magnetic tape. Later, when you press play, an electric signal goes from the tape to the speaker, and you retrieve the message.
Racing data acquisition systems are much like phone answering machines. But instead of using a microphone, they use sensors to measure engine rpm, vehicle speed, pressure, or movement. The magnetic tape on the answering machine is replaced by a digital "data logger" on the race car. The main difference with a data system is the "replay" portion. Instead of the speaker in the tape recorder, the racing data stored in the logger is displayed via computer software.
This tiny sensor measures g-force. It is best to mount the sensor to the rollcage and not
The exciting aspect is that race car sensors are measuring "the real deal" on the racetrack, and the logger box is recording it all the way around the track, lap after lap. Problems that happen very quickly on the racetrack can be replayed back in the pits. You can replay it in slow motion or even freeze-frame to pinpoint something that happened in 11/450 second on the racetrack.
In addition to capturing events that happen quickly, many other events can be captured, too. Data that determines what the chassis, engine, and driver did on the racetrack is neatly saved for examination 15 minutes later, or when you get home, or even next week. This can be a great stress reliever because you don't have to digest the information at the racetrack when other priorities demand your attention. Another advantage is that you don't have to remember to write every detail in a notebook.
In our illustrations, you'll see a marker beside the device. This will give insight into the size of each particular item.
Data Sensors Sometimes the hardest part of using a data acquisition system is deciding what you want to measure. There are sensors to measure just about every aspect of your race car, especially for the chassis, engines, and even the driver.
Wheel Position Data Wheel position sensors are a typical part of a circle track data system. They look like a skinny little shock and are often called data shocks. Data shocks are mounted just like your regular shocks. One end is attached to the frame and the other to the rear axle or lower A frame in the front.
Without data acquisition, wheel travel is typically measured by the position of the rubber grommet on the shock absorber. This method only measures the maximum compression travel from the last time you reset the shock rubbers and requires the measurement be taken on a flat and level surface. The advantage of data shocks is the ability to continuously measure wheel travel all the way around the racetrack. Rebound and compression travel are recorded-not just the compression displacement of the old shock rubber. You will know the suspension travel at every point on the racetrack.
Here's where chassis people get excited. By having data shocks on all four wheels, the wheel position information can provide even more information. For example, comparing left and right wheel positions gives you the ability to measure body roll. You can tell if the chassis is rolling up or down and where that happens on the racetrack. Likewise, you can measure dive, squat, or ride heights at any point on the racetrack.
Typically, the largest component in a system is the data logger box. This photo is a 38-ch
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 system is not located on the race car, but positioned track
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.
Other Data There are infrared sensors that measure tire temperatures, air pressure sensors for aerodynamic work, and torque-sensing driveshaft yokes. You can find sensors to measure tire pressure, spring load, and force on suspension components. If you have the budget and want to measure anything, there are sensors to do the job.
The Box (Data Logger) Once you have your sensors mounted on the race car, you need a box to record all of the measurements. Data loggers are a lot like stereo equipment. The average user can't tell the difference between the best high-end unit and a very good mid-level unit, but understanding what you need in a box can make a difference of thousands of dollars at the cash register.
For the average racer, there are two main items to understand about data loggers: number of signals and memory. The old phone answering machine had one signal, the microphone. Data loggers can have many signals, often called channels. Each sensor you place on your race car will require a channel. So, in essence, the data logger is like several tape recorders built into one unit.
Box Size Boxes come in many different configurations. There are little four-channel boxes on the low end of the scale that cost around $600. These are basic units and typically are not expandable. Next are the expandable units that all have roughly the same box size, but allow more channels to be added in the box. Adding channels increases the cost, but midsized units (12-16 channels) start around $1,200 and go to $2,000. High-end boxes have 30-38 channels and can cost $2,000-$5,000, depending on other factors.
Once you start using a basic unit, you may find it confining, but midsized units are more than adequate for weekend racers. For example, if chassis setup is your priority, a midsized unit will allow you to record four individual wheel position channels, steering, brake, throttle, engine rpm, two wheel speeds, two g-force channels, and have some open channels. If engines are your game, then you could have engine rpm, wheel speed, driveshaft speed, water temperature, air temperature, fuel and oil pressure, manifold pressure, eight EGTs, throttle position, g-force, and more. In either case, a midsized unit can handle the load at a reasonable price.
Memory Memory in a data logger is like memory in your home computer. It will take more memory to save a 50-lap main event than a 5-lap test run. Basically, more laps equals more data, and more channels equals more data. Typically, a unit comes with a given amount of memory, and you have the option to purchase more memory. Boxes come with as little as 128K or as much as 4 meg of memory. Even for professional circle track racers, 2 meg of memory tends to be a reasonable quantity. However, some midsized boxes come with 2 meg at no extra charge, so it pays to shop around.
Memory influences the length of recording time, but sample rate has a big impact, too. Think of samples such as the individual frames on a movie film. One frame per second makes a real jerky movie, where 10 frames per second is barely jerky. However, the added frames require more film. Likewise, a higher sample rate uses more memory. Data systems typically run between 10 and 100 samples per second, and some units go as high as 400 samples per second. The question of what sample rate should be used will likely prompt a long debate between engineers, suppliers, and data geeks. Just keep data rate in mind and realize it will impact your recording time.
The Beacon Just like the beep between messages on the phone answering machine, a marker is needed in your data. A lap timer beacon is used with data acquisition systems to signal the end of one lap and the beginning of another. Basic data systems use infrared lap timers already used by many local racers. High-end systems use a multi-IR beacon, but work on exactly the same line-of-sight principle.
Because the beacon sensor is connected to the data logger (box), it will require a channel. Using a channel is a small price to pay when you see how much more information you get by breaking the data into laps.
At or near the start/finish line tends to be the best location to place the beacon. The car's position on the track (line) will be relatively consistent by doing this. Also, the race car is always accelerating at that point, providing a much more consistent condition, and the data lap times will be similar to typical track lap times.
This concludes the cost and basic hardware aspects of data acquisition systems. Next month the replay portion of the system will be covered. You will get to see how software is used to display the sensor information and where the race car is on the track. In addition, you will see real data with tips on how to use this information to make your race car faster.