Track Time (NHRA Time)

The following procedure illustrates how to create a math channel in the DataLink II software to show the elapsed time from your E.T. slip. Why is this channel necessary? Let us give you a quick explanation.

As many of you know, on the starting line at most tracks are the pre-stage beam and stage beam. Quite often there is a third “guard beam” as well, but we will disregard that for the time being. For the sake of this example, let us assume that the NHRA or “Track” timing system begins when the vehicle’s front wheel travels the “rollout distance”, which is usually about 12 inches. That means that the vehicle must travel this distance before the timing system knows that the vehicle has left the line. In almost every drag racing vehicle, from Super Street to Top Fuel, it takes approximately 0.24 seconds for the vehicle to travel this initial distance.

That means that if your E.T. slip shows “8.900” for an elapsed time, the downloaded file from your data logger will show you crossing the finish line at 9.140 seconds, since the data logger recorded the movement nearly one-quarter of a second before the timing system saw the front tire leave the stage beam.

Since it can be difficult and sometimes confusing to keep this time offset in mind when viewing your data, we encourage racers to add a channel called “Track Time or “NHRA Time” to help them more accurately correlate their data with their E.T. slip. This channel is very important when trying to display other DataLink formulas, like Intervals, G-Meter MPH and G-Meter Distance.

First, open the file to which you wish to add the new channel. If it is a run file, simply open it from the ‘File’ menu in the DataLink II software. If you wish to add it to your configuration file, so the channel will appear in all subsequent downloaded files, the select ‘Open Car Configuration’ from the ‘File’ menu, and select the appropriate configuration file from the available list.

Once the desired file has been opened in the software, select the ‘Channel Maintenance’ option under the ‘Edit’ menu.

Click on the channel in the list where you would like to insert the new channel. In this example, we have selected a position after the last channel, so the position after ‘Pan Press’ has been highlighted. Click on ‘Easy Insert Channel’.

Now we need to select the type of channel we will be inserting. Since this is a simple expression, we will select “Calculation’ and under the Type, we will select expression (EXPR). Click ‘OK’.

Click on the text box beside Name and enter the desired name, either ‘NHRA Time’ or ‘Track Time’. Then click in the Expr: text box and then scroll down through the list until you find the timer channel called Timer_100sps. Double-click on it so that it appears in the expression text box and then subtract the offset, which in this case is 0.024 seconds.

Also, be sure to scale the minimum and maximum values correctly for your application. We recommend the minimum value is ‘0’ and ‘9999’ as the maximum. In this example from a Top Fuel car, the maximum has been set to ‘330’. You may wish to change the result units to ‘S’ (seconds).

Simply click ‘OK’ to add the channel to the list, and then ‘OK’ a second time to return to the main screen of the DataLink II software. You should see the channel button ‘Track Time’ appear in the location into which you inserted it. If you are satisfied with the results, be sure to click ‘Save’ from the ‘File’ menu.

For questions or assistance in adding these channels to your system, please contact us at Performance Data Systems at (949) 652-6300 or email us at