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5. Data Processing with MS-Excel

To process the data a relatively simple spreadsheet can be made. These spreadsheets are often available online for download, or you can make your own. Most excel users can create the spreadsheet based on the instructions below.

The spreadsheet consists of 3 sections.


This is a 20x20 grid where you paste in the logged AFR data. When using spreadsheets to tune you need to delete any bad data points. Engine braking, and erroneous points need to be removed. Rows P1 and P2 should be deleted. Often it is a good Idea to tune the idle manually, and to delete the idle region form the pasted AFR data as well. Delete these in the Input section.


This is a 20 x 20 grid where you define the desired AFR. Desired AFR should consider the very different requirements for idle, cruising, midrange, high boost and high RPM. AFR is often a blend from a cruising range of 14.7:1 to a full boost value of ~11.0:1 for a turbo rotary. The idle AFR may vary depending on the engines state of tune. There is some debate on what is the best AFR and this should be researched carefully before tuning. A desired AFR graph used successfully on a single turbo street ported RX7 is shown below.


This is another 20 x 20 grid where the Pasted AFR values are compared to the desired AFR values, and a correction factor is calculated. In MS excel the equation for these cells is as follows: CELL =IF(OR(ISBLANK(B3)),1,((B3)/B27)) Where B3 is the pasted AFR value and B27 is the desired AFR value. Should the input be blank, the value will be 1, otherwise it will simply divide the actual AFR by the desired AFR

As an example if the AFR is 14.0 and the desired AFR is 10.0 then the correction factor is (14/10) = 1.4. The spreadsheet will add 40% more fuel to obtain the desired AFR. Figure 14 is the correction factor map based on the input data and the desired AFR grid.

6. Using Processed LM1 Data with FC-Edit

1. To move the logged data from the Map Watch to the spreadsheet a simple copy and paste operation can be used. Highlight the 20x20 grid and press Ctrl+C to copy. Right clicking and selecting copy works on the newer revisions of the FC edit. Be sure to highlight all of the data. This can be done on the fly while tuning the car. Usually stopping the logging and copying the raw logged data is best. The logs can get rather large and difficult for a laptop to save and open later. Copying the data on the fly ensures you won’t lose it.

2. Pasting the data into the 20 x 20 grid is just as simple. Highlight the 20 x 20 grid in excel and press Ctrl+V to paste the data, or right click and paste. Be sure to have the data aligned properly in the grid. If the data is shifted, it will seriously skew the results of tuning.

3. After pasting in the data it needs to be cleaned up to remove any bad data points, engine braking, and any areas that we do not want to modify (idle range perhaps).

4. To input the correction values into the FC edit file, we need to first reset the injection correction map to all 1’s by recalculating the base map. The FC edit has 2 maps that are used to determine the fuel quantity provided to the engine. There is an Injection Correction map, and a Base Map. These two maps are multiplied to calculate the injected fuel. There are several other factors that get used to determine the actual fueling, however they are beyond the scope of this document. Using tools – Recalculate base map, the FC-edit software will perform this multiplication and adjust the base map while setting the correction map to 1.00 in all cells.

After recalculating the Base Map, the INJ MAP will look like figure below.

5. Now that the INJ MAP is all 1’s, we can paste in the correction values from our spreadsheet. Highlight the 20 x 20 correction values from the spreadsheet press Ctrl+C, or right click Copy.

6. Highlight the 20 x 20 INJ MAP and paste in the data by pressing Ctrl + V, or right click paste. Be sure to have the complete grid highlighted. The new INJ MAP should look like figure 17. Be sure to verify that the numbers pasted are in fact the numbers from the spreadsheet. They should be numbers close to 1.00. A number of 1.10 will add 10% fuel ad a 0.90 will subtract 10% fuel. Unless the car is running really rough, try to avoid large changes of %30+.

7. Save the new FC-Edit file and write it to the ECU by clicking Update.

8. You have now completed logging and correcting based on the logs. The AFR values should be quite close to the desired AFR after only 1 or 2 sessions. It is important to drive the car, or dyno test the car under all boost and RPM conditions where it will operate to ensure that all cells are modified. After each logging session the data collected needs to be pasted into excel for processing then copied and pasted back into FC-Edit. Each time data will be pasted into FC-Edit it is important to recalculate the base map and reset the INJ MAP to all 1’s before pasting correction values.

9. It is often a good idea to start with a rich running car, and then remove fuel by tuning. Starting with a lean car can be dangerous because of engine knock, and high exhaust gas temperatures. Rotary engines are particularly sensitive to lean mixtures, and easy to damage. If you have a generally lean mixture, go into the INJ map and add fuel almost everywhere by changing all values to greater than 1. A general rule of thumb is that 10% extra fuel will lower your AFR by a full point.




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