CC’s Per Turn

The following procedure illustrates how to create a math channel in the DataLink II software to use your Fuel Flow channel to detect changes within your fuel system.

CC’s Per Turn is a very useful channel, as it is a direct comparison of Fuel Flow to Engine RPM. Therefore, if the value changes throughout the RPM range of the engine, and no bypass jets are being either opened or closed, there may be an issue with the fuel system. When bypass jets are opened or closed (more commonly referred to as “leanouts” or “richening circuits”), the CC’s Per Turn channel will clearly show when these events occur, as there will be marked “steps” in the channel, because the Fuel Flow values change dramatically in relation to Engine RPM.

Looking at the run below, you can see that the efficiency of the fuel pump begins to fall off as the Engine goes above 8700 RPM. After the shift, the RPM drops back down and the CC’s Per Turn continue on at about 9.15-9.20 CC’s.

To add this channel, 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 will be placing it immediately after the ‘Fuel Flow’ channel, so we will highlight the next channel in the list (‘TDC RPM’). Click on ‘Easy Insert Channel’.

Now we need to select the type of channel we will be inserting. Since we are going to create a simple expression, we should select ‘Calculation’ from the list and then select ‘EXPR’  as the type . Click ‘OK’.


Name the channel ‘CC’s Per Turn’, or something  similar. Place the cursor in the ‘Expr.’ line, and then select ‘Fuel Flow’ from the list of ‘Currently Defined Channels’ by double-clicking on the entry in the list. Then, multiply that value by the constant to convert gallons to CC’s by typing ‘*3785’. Then, divide by Engine RPM by using the ‘/’ character and then double-clicking on the ‘Engine RPM’ channel in the ‘Currently Defined Channels’. The completed expression should read as ‘Fuel Flow’*3785/’Engine RPM’ as shown below.

Finish the channel by setting the decimals to 3 digits after the decimal point and result units to CC’s. The minimum result value should be set to ‘0’ and the maximum should be set to ’10’ for supercharged gas and methanol and even nostalgia top fuel/funny car. For supercharged nitro, the maximum should be set to ’40’.

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 ‘Distance’ 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 support@racepds.com.