Subaru Rally Team Engineer: Jonathan Carey
Tom's Hardware: Clearly, building a race car requires a lot of work and testing. How do digital data acquisition and data logging help improve the design and build process of a rally car?
Jonathan Carey: Data acquisition and logging are fundamental to the test and development of a rally car. The core design evolves around objectives that are established from calculations based on driver feedback, chassis and powertrain data, and stage performance data. Data logging gives us an accurate history of all working conditions at any point during a rally by taking time-based values for each area and displaying them as either a chart form, scatter plot, bar chart, histogram, or value report.
During testing, we log information anywhere from 200 to 1000 Hz to gain more accuracy and allow certain areas of the car to be focused on more intently.
Tom's Hardware: What kind of information do you record during races and testing sessions?
Jonathan Carey: Data logging allows us to collect accurate information from multiple areas of the vehicle, including its engine, transmission, suspension, and cooling systems. We get:
- Engine RPM
- Engine pressures: oil, boost, fuel, coolant, and barometric pressure
- Engine parameters: throttle angle, ignition advance for all cylinders, fuel injection condition for all cylinders, and wastegate position
- Temperatures: engine coolant, engine intake manifold air, oil, and fuel, transmission oil, and rear differential oil
- Transmission: speed, wheel speeds, differential condition, speed difference from front to rear wheels
- Chassis: acceleration rate
Tom's Hardware: What are you using to log the data?
Jonathan Carey: We use a USB data logger from General Engine Management Systems (GEMS) that we can quickly remove from the rally car and download information to a computer. This logger is only 1" x 3/4", weighs only a few ounces, and can store up to 32 MB of data. In our event setting, that means recording continuously for two hours. There are much larger options available; however, this give us the best balance between data captured and the time available during service to process it.
Tom's Hardware: What can your team do with the data they collect during the course of a race?
Jonathan Carey: Data is stored from all events and tests, and is then processed whenever it's needed according to the area of the car that is being focused on at any particular time. As an example, the development of differentials can be affected according to wheel speed information, vehicle handling characteristics, and engine conditions.
During an event, the data is inspected at each service point to confirm that the vehicle is functioning within pre-defined limits. Any areas outside of those limits are investigated and acted on. The data is also reviewed for performance improvement reasons, and to identify any potential improvements in vehicle handling or driving technique. The latter is used to help aid the driver make better use of the vehicle, and also to improve the programming of the vehicle functions to better suit the driver's style and preference for any particular conditions.
Tom's Hardware: Do you consider yourself a tech geek?
Jonathan Carey: I would not consider myself a tech geek. I am interested in technology as far as it applies to my professional role, but that's about as far as it goes.
Tom's Hardware: What's your daily driver?
Jonathan Carey: A Ford Fiesta SportVan.