MK8 / 8Y Datalogging Review

Intro to Datalogging

Whether you own a stock daily driver or a dedicated track car, keeping tabs on how your car is running is vital to making sure your car will last without needing expensive repairs.  While monitoring gauges on your car can let you know what is happening with a few parameters at a given moment, it won't be able to give you a full scope of how the car is running. In order to gain perspective over a wider range of time and parameters, we run a datalog.

Here's a good reference on how you actually create a datalog
How To: Datalog

What is a Datalog?

A Datalog is a file taken by the Accessport where it records a user-specified set of sensor data and/or information which the vehicle's computer is using to run the engine. This can include things from simple data like coolant temperature or boost, to how often the computer wants the fuel injector to be open during a given engine cycle.

Why Can't I Datalog Everything?

While each generation of ECU has different limitations there is generally a limit to the number of parameters you can select.  In most cases this is because the ECU needs to process the requests for data and output that information to whatever device is requesting it.  As a result, the more monitors you request, the more work the computer has to do in order to keep up.  On some vehicles as you approach the limit you won't see any differences until it simply cannot log more items.  However, on other platforms you will see the approach to the limit show itself as a slow down in the logging rate, so if you are logging a bunch of different items make sure to keep an eye on the amount of time in between each sample to keep things in perspective.

Things Every Good Datalog Needs

A Map with no reference points is never going to help you get from one place to another.  There are a few parameters that do wonders for helping to put other monitors into context, as well as showing your environment and driving style.

• RPM

•   This lets us see what speed the engine is moving at in Revolutions Per Minute.  Additionally, conditions of acceleration, deceleration, and maintaining a steady speed will all cause variations in the fueling, ignition timing, and boost.

• Throttle Position (ETC Angle or TPS)

  • How far open the throttle is open changes airflow to the engine and when combined with the RPM helps to give an indication of the amount of load the vehicle is under.

• Accelerator Pedal Position - APP

  • Measures the amount the accelerator pedal is pressed down by the driver.  Does not always equate to the same amount of throttle position and can give us additional information similar to what throttle position offers.