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If you take your car to the drag strip, road course or autocross track then you need to know what your vehicle is doing. If you've modified your car with ported heads and a cam, or added a turbo or blower, or you squeeze a little nitrous oxide now and then, you really need to know what your vehicle is doing. What you don't know can hurt you, or at least hurt your engine.
Enter data logging, which is an electronic device that records data over time via remote sensors. Data logging can be as simple or as complicated as you want it to be. In this two part series we're going to show you how to data log via your late model HEMI's OBDII port with a Diablosport Trinity and via dedicated sensors with an AEM Electronics AQ-1 data acquisition system.
Let's start with the basics, why do you need to data log? If your vehicle is mostly factory stock with just a few bolt-ons like cold air intake, cat-back exhaust and the like then you probably don't need to data log unless you're planning on bigger mods later and want to know what your engine is doing in its current state. However, if you have the previously stated power adders installed, then a small investment in data logging may save your engine someday. If you compete in bracket racing, autocross, or open track racing, then if you want to improve your performance you have to data log if you want to be at the front of the pack. We're going to talk about data logging at the drag strip in this story because that's what we do. But the same equipment and principles apply to whatever kind of racing or high performance driving that you do.
If you're not data logging currently, then you really only think you know what your vehicle and engine are doing. You think you're spinning the tires at launch, but you may be over-hooking and going into wheel hop/tire shake and not even know it. The difference is critical, because what you do to cure true tire spin at the hit is the exact opposite of what you do to cure wheel hop. You think your air-fuel ratio is good because you have the data graph from when your tuner tweaked your engine controller on their dyno. But do you know exactly what your A/F ratio is like through all of the gears in the real world? Your tuner's graph is for wide open throttle in one gear only and in the temperature and humidity that was present at the moment it ran on the dyno. How's your air fuel health in every gear and at different altitudes and temperatures? The answer can be the difference between doing well at the track and going home in one piece and having your engine detonate very expensively on the track.
We've been using our Diablosport Trinity to data log our runs for almost four years now and we have a lot of data and experience with it. Installing the unit with a zip tie and the included suction cup mount can take as little as one minute for the physical mounting. The Trinity is primarily a hand held PCM programmer, Diablosport products are almost ubiquitous among late model HEMI fans, from the older Predator to the new Trinity and inTune devices. Each of the devices have available "canned" tunes from Diablosport that are safe and easy to upload to stock or near stock vehicles for improved performance and drivability. Beyond that level, custom tuners can create one-of-a-kind tunes for your modified vehicle using their advanced Diablosport software and a dyno. Custom tunes are then uploaded to the car's PCM (engine computer) with the device connected to the OBD II port under the dash.
For data logging, the Diablosport devices can pretty much log any PID (Performance Information Data) information that is monitored by OBD II mandated vehicles. This includes things like Engine Coolant Temperature (ECT), Inlet Air Temperature (IAT), base and actual spark advance, manifold pressure, throttle pedal and throttle blade position, and lots more. Our Trinity can also log up to two external analog 5v sensors. We used our two analog channels for reading A/F ratio with an Auto Meter gauge that reads from a dedicated O2 sensor which can send an analog signal to a logging device. We also used an AEM Electronics fuel pressure gauge that could read from a dedicated sensor on our fuel rail and also can send a 5v analog signal.
Note that (oddly) air-fuel ratio is not a PID that is monitored by OBD II compliant engine controllers. The only way to know you're A/F ratio with any data logger is to installed an additional O2 sensor to your exhaust and hook it to a device that can read the sensor and pass the signal to a data logger.
We're excited about expanding our data logging capabilities with the addition of the AEM AQ-1 data logger. As a dedicated data logger, all of the hardware is optimized for just one job, logging data. As a true Sportsman racer's data logger, the AQ-1 requires external sensors for all of the information you'd like to log (no reading the OBD II here since race cars don't have emissions requirements and equipment). The AQ-1 has extremely high sampling rates, which means smooth and accurate data traces for each channel monitored. It has a built-in three-axis accelerometer as well as built-in battery voltage monitoring. You can log up to eight channels of data and trigger up to three digital switch channels (such as nitrous controllers, boost controllers, clutch activated devices, etc.).
Brand new to the AQ-1 and a real boon to Sportsman drag racers just getting into data logging is AEM's "Drag Race" set up file that allows users to quickly begin using their AQ-1. By installing pressure, temperature and other sensors for popularly logged parameters into pre-determined inputs in the "Drag Race" set up software you can start logging right away with no need to calibrate any sensors, and view data without having to create a template in the "AEMdata" analysis software.