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Practical Diesel Tuning: Data Logging

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Data Logging


00:00 - As we've briefly touched on already, one of the most daunting aspects of reflashing for those coming from a standalone ECU tuning background is the inability to make tuning changes in real time.
00:10 With a conventional standalone ECU, we can adjust the numbers in any of the tables and instantly we see the result of these changes on the dyno.
00:16 As we discussed earlier, in some instances live tuning may be an option for some ECUs however the much more common technique is to take a datalog from the ECU and make changes based on the data you see.
00:27 This means that datalogging plays a critical part in successfully and accurately being able to reflash a factory ECU.
00:34 If you're buying a commercial reflashing package then it'll come with the datalogging software while in the open source community there are various logging options available that you will need to download.
00:43 Some of these may be free while others may be a modest investment.
00:47 You will see the datalogging in action in the worked examples later in the course but in this module we'll discuss what we're trying to get from our datalogs and what parameters we may want to look at.
00:56 One aspect to consider is that there may be a huge amount of data available that we can potentially log and the data we need to view will depend on the specific task we're trying to complete.
01:07 It might sound sensible then to simply log all the parameters available.
01:11 And then you're certain to have access to the data that you need.
01:13 The problem with doing this is that there's often a limit to how much data can be sent through an OBD2 port and if you log multiple parameters, this can result in the parameters being logged at a slower rate that isn't useful for the purpose.
01:25 For fast moving inputs such as engine speed, manifold pressure, fuel pressure, or injection timing, we need a reasonably high logging rate.
01:33 20 - 25 hertz as a minimum to get useful data.
01:36 Slower moving inputs such as inlet air temperature or engine coolant temperature don't change quickly and therefore slower logging rates are OK.
01:44 1 - 5 hertz is OK.
01:45 The amount of control over the logged parameters and the logging rate will depend on the vehicle you're tuning as well as the logging software that you're using.
01:53 The actual parameters that are available to log will depend on the ECU you're working with anD not all parameters are going to be available on all ECUs.
02:02 The actual parameters you want to log are often defined by what's referred to as a PID which stands simply for parameter ID.
02:09 And these PIDs are used by the datalogger to request data from the vehicle's ECU.
02:13 While all manufacturers are required to make available certain PIDs, mainly for the purpose of checking emissions compliance, many other PIDs may also be available which may be useful for technicians servicing the vehicles or diagnosing faults.
02:27 I won't bore you by listing every useful PID but some of the key ones that I like to use, engine speed, boost pressure, fuel pressure, injector pulse width, fuel quantity and injection timing just to name a few, in particular logging fuel quantity and engine speed will allow you to see where in a particular map the ECU is accessing at a certain point of the datalog.
02:48 As well as logging PIDs that are internal to the ECU, it can be useful if we can also input additional sensors such as exhaust gas temperature and air/fuel ratio into our datalogger so we can see exactly what these parameters are doing at any point in the log file.