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CarChip E/X A tiny data logger that plugs straight into your car By JULIAN EDGAR N OW HERE’S a brilliant dev­ice – it plugs into your car’s standard On Board Diagnostics (OBD) port and then proceeds to log car data up to a maximum of 300 hours running. You can log parameters like road speed, RPM, oxygen sensor output and the airflow meter signal. Then you unplug the device from the car and connect it to your PC where you can easily graph and analyse the information, including quickly highlighting high acceleration and braking rates, maximum speeds and so on. It’s ideal for someone who wants to monitor how their car is being driven by others (parents of teenage drivers, anyone?) or to check on the health of engine management sensors. And 22  Silicon Chip talking about the latter, the device will also record fault codes and can then be used to clear them! The CarChip E/X The CarChip E/X is only a bit bigger than the OBD socket itself. So what’s an OBD socket then? Mandated in the US about 10 years ago, the OBD port is a standardised diagnostics socket that allows the US authorities to quickly and easily diagnose engine management maladies that could cause the car to be no longer emissions legal. With the legislated requirement that the socket be fitted and that a standardised protocol be used (actually, a number of protocols are permitted), car manufacturers also adopted the system for their own diagnostics. However, the manufacturerspecific data is in addition to the OBD data. In other words, all cars sold in the US have an OBD socket with certain standardised information available from it, while manufacturer-specific diagnostics tools can access further information that pertains to just that model. The CarChip E/X makes use of the universal OBD data – vehicle speed, engine speed, throttle position, coolant temperature, engine load, intake manifold pressure, airflow rate, intake air temp, ignition timing advance, fuel pressure, short-term fuel trim, longterm fuel trim, oxygen sensor voltage, battery voltage and fuel system status. siliconchip.com.au The PC interface cable plugs into this socket (arrowed) and connects the CarChip to the PC’s USB port. Dedicated software is used to analyse and display the data. The CarChip E/X plugs straight into the OBD port now found on most cars. It continuously logs data that can include speed, throttle position and engine RPM. Note that many cars will not support all of these parameters (for example, a car with a MAP sensor will not support airflow rate), so this is the maximum possible list of parameters able to be generically read from the OBD port. At any one time, a maximum of four parameters is able to be logged by the CarChip E/X. Configuring the CarChip E/X After the software is loaded on the PC, the CarChip E/X is connected via a dedicated USB adaptor cable. A “Walkthrough Setup” procedure is then initiated that allows the user to select metric or imperial units, the name of the vehicle and driver, the CarChip serial number and whether the data is automatically cleared from the CarChip when it is downloaded to the PC. Under the “Choose Other Parameters” tab, you can set what parameters you want logged. These can be set to be logged at 5, 10, 20, 30 or 60-second intervals. Thresholds can also be set for what is defined by the data analysis software as hard braking, extreme braking, hard acceleration, extreme acceleration and various speed bands. The braking and acceleration levels are presumably determined by the change of speed over time. The software is largely self-explanatory and is quite easy to use. Installation Installation of the CarChip E/X in the car takes only a few seconds. Step 1 is to locate the OBD socket. By regulation this must be positioned near the steering wheel and it’s also siliconchip.com.au Fig.1: this screen grab shows the output of one of the oxygen sensors, logged over the trip shown in Fig.2. This shows that (a) the oxygen sensor is in good health (the output rapidly varies a great deal) and that (b) the car ran fairly lean mixtures for much of the time (output voltage mostly below 0.5V). Logging the short and long-term fuel trims would indicate if these mixtures were leaner than desirable – if they were (say because of a blocked fuel filter), the fuel trims would show major change. required that it be accessible without tools. Common positions include under the steering column, under a trim panel in the centre console or up under the dash. Step 2 is to plug the CarChip E/X into the OBD socket. Step 3 is to start the car and make sure the data logger indicator LED on the device is flashing (if this LED is distracting, it can be configured off in the software). And that’s it for installation! The unit is now ready for use. Analysing the Data The CarChip E/X stores data for up to 300 hours of driving and then starts over-writing the oldest data. However, at any point, you can remove the device from the car and download the data to your PC which then displays it in the form of separate trips. For each trip, you can display the October 2006  23 The CarChip E/X package consists of a PC interface cable, the CarChip plug-in module and a software CD. logged parameters in graphical or tabular forms. In addition to the logged parameter, each graph also shows where acceleration and braking thresholds have been exceeded. A report can then be brought up that shows various data, including the start and stop times of the trip, amount of time spent in each speed band, distance, average and maximum speeds, and hard braking and acceleration events. Even a glance at this information will show how the vehicle has been driven. Sensor graphs The graphs of the sensor outputs can be used to assess the “health” of This report shows a logged trouble code. In addition to the trouble code number being cited (P1447), the report also shows the engine parameters at the time the code was logged. This information makes tracing intermittent faults much easier. 24  Silicon Chip the sensors used in the vehicle. For example, the oxygen sensors used in most cars should show a swing from about 0-1V. A dead oxygen sensor will not only have a low voltage output but quick changes will also be absent. However, for diagnostics, the first step should be to view the Vehicle Trouble Log. This displays any logged fault codes and significantly, also shows a snapshot of engine parameters at the time the fault code was logged. These parameters include intake manifold pressure, coolant temperature, calculated load value, engine speed, vehicle speed, short and long-term fuel trims, and whether the engine management system is working in open or closed-loop operation. Note that these snapshot parameters are not dependent on the parameters you have chosen to log long-term. It’s important to realise that the logged trouble codes may be manufacturer-specific. The software gives a guide as to what each trouble code may mean but these are not always correct. Instead, it’s best to use Google to determine the meaning of a trouble code (eg, “Honda Insight P1447”) rather than relying on the suggestion. The software can also be configured to delete the trouble code but again, this may not be successful if the trouble code is manufacturer-specific. siliconchip.com.au Fig.2: this screen grab shows the speed log of one trip. The timings on the horizontal axis show that the trip started at 1:55pm on July 29 and finished at 2:13pm. The vertical red trace (arrowed) indicates a hard braking event. The threshold for this (as well as extreme braking, hard acceleration and extreme acceleration) can be user-set. At right is the report for the same trip. At a glance, it can be seen that there was one hard braking event, no hard acceleration, most of the time was spent at less than 72km/h (in fact, the average speed was 61km/h) and the maximum speed was 97km/h. These reports are invaluable when driver behaviour needs to be monitored. The software also includes the ability to replay the vehicle speed for the 18 seconds prior to a sudden stop. The software calls this an “Accident Log” and it may be useful where the vehicle is involved in an accident. However, for various reasons, we think such information would easily be able to be challenged in a court of law. Conclusion The CarChip E/X costs $286 plus $7.70 postage. A cheaper version (the CarChip), with a shorter 75-hour logging capability, is available for $217.80. For your money you get an effective and small data logger that can remain plugged into the car semipermanently. It will clearly show how the car is being driven on each trip. It also reads fault codes and is able to Will It Fit My Car? The first step in determining whether the CarChip will work with your car is to see if it has an OBD port. However, that is not the end of the matter. Many cars sold in Australia were produced with an OBD port but the internal ECU software to output OBD data was not enabled. For example, Toyota and Lexus models of around 1988-1990 have an OBD port but OBD readers will not work with them. Cars produced after about 1991 that have an OBD port and which were also sold in the US are highly likely to have OBD capability. Australian-built cars with an OBD port may or may not have OBD capability. Again, the more recent the car, the more likely an OBD reader will work. The CarChip works with the following OBD protocols: J1850-41.6, J185010.4, ISO9141, KWP2000 and CAN. clear some of them. Furthermore, if you need to monitor sensor outputs (useful if the car is being modified), then the CarChip will do that as well. For further information, contact Ecowatch on (03) 97617040 or browse to their website at www.davisinstruSC ments.com.au Issues Getting Dog-Eared? Keep your copies safe with our handy binders Available Aust, only. Price: $A12.95 plus $7 p&p per order (includes GST). Just fill in and mail the handy order form in this issue; or ring (02) 9939 3295 and quote your credit card number; or fax your order with credit card details to (02) 99392648. siliconchip.com.au October 2006  25