AEM F/IC6 and M45 Tuning

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and M45 Tuning

I finally got the AEM F/IC6 installed in March 2015 and ready to run. Now all that is left is to tune it. I called AEM support to get the unit working. They flashed the unit and helped me to be sure it was working.

I tested the unit by loading a zeroed out calibration file and disabled boost so the car would run on the OEM ECU. It ran fine. No issues. The wires were all connected correctly and now I could try tuning the F/IC6 to the M45 supercharger.

I got in touch with Roger and with a file he had started we got together to tune it to my car. We ran into a harsh stumble that we could not tune out. That is why it has taken me so long to get to posting this. I could not find the issue. Below is what I did trying to get the stumble out of the tune.

This is where I was as of May 2015.


  • The vehicle is a 2000 Miata SE with a stock M45 Jackson Racing supercharger (4-5 psi). The car has around 90K miles on it with the last 10,000 miles being run very successfully with the M45 supercharger and only a non-adjustable Powercard for control.

  • The supercharger now had about 60K miles on it. I bought this supercharger with 50K successful miles on it.

  • The F/IC6 was purchased to allow for better fuel control, timing control and to allow for later installation of 62.5 mm pulley for 2 more psi. F/IC6 installed on the M45 in attempt to tune it before installing upgrades.

  • I made a patch cable from an AEM harness extension. It was tested before and after installation. 1K resistor installed on O2 lead.

  • AEM analog UEGO connected and included in logging.


  • The engine stumbles while slowly accelerating in gears 2-5 and only when just at boost where O2 map forces Open Loop (usually about 3000 rpm). It feels like ignition stops for a second but then runs smoothly after one or two stumbles.

  • The O2 map is set at .19 in all the cells starting at 14.7 psia (0 psi) up to maximum boost to cause the ECU to go into Open Loop and use the fuel map in FIC.

  • The logs show a sudden increase in AFR while the injectors stay on a smooth curve which may be caused by sudden stop in ignition signal. This is usually from around 2-3 points on AFR recording. (While this is probably not the problem, I think it indicates the sudden stop in ignition.)


  • Boost disabled and FIC file with all zeros runs the car fine.

  • Fuel map changed to add and delete fuel at transition into boost.

  • O2 map changed to switch to open loop sooner and above 0 psi. Also tried .43 prior to 0 psi which caused additional hesitation, but stumble remained after hesitation.

  • Acceleration settings changed multiple times including using zeros in all cells.

  • Zeroed the F/IC6 calibration file and Powercard reinstalled. Car ran great again without hesitation.

  • Recalibrated the TPS.

  • Installed new plugs and decreased gap to .030.

  • Called AEM and talked to Matt. He suggested swapping the F/IC6 and maybe the OEM ECU.

  • Replaced this new F/IC6 with another new F/IC6 (I have two).

  • Roger suggested verifying the F/IC6 it was running the 110 hex file. I could not find out how this was done. I had used the support desk at AEM to help me flash both the units when I bought them and I had talked to them again about the problems so I decided this was not necessary since they are the experts on their equipment.


  • Swap and re-calibrate TPS

  • Swap OEM ECU

  • Fiddle with the O2 resistor


  • The engine runs beautifully when given sudden WOT through all the gears without knock.

  • The car runs fine with no knock at all other times and is driveable.

  • The stumble is disconcerting since I believe it must be something that should fixed.

  • Plans to improve the tune and install the upgrades on the M45 are on hold until the stumble is fixed.

  • I have another F/IC6 to put on a M62 BRP hot side supercharger, so need to find problem now for the M45.

At this point, I was considering abandoning the F/IC6 and going back to the Powercard. Nothing I had tried seemed to make any difference to the stumble. I contacted Ken Hill to see if he could help.

Ken was very busy at the time I contacted him but he did offer some suggestions. After trying his suggestions, I was still stumped by the stumble. I just could not identify the source of the problem. I let the car sit for another three months without hardly touching it.

My son Matt then contacted Ken Hill and Ken offered to look at the calibration files we were using and help us try to tune out the stumble. He was very patient with us and sent us six or seven different calibration files to test and log. However, the stumble persisted.

I decided to make a video of logging the next calibration file results so he could hear the stumble. He suggested that the hex file was wrong, or the F/IC6 had a fault. But he also included a link to an AEM video on how to determine the hex file now in use and how to re-flash the unit if needed.

This time I did not call AEM support and instead used the information in the video to find out which hex file was on both the F/IC6 units. Roger had told me early on that I needed to check this but I did not since I had used AEM support reps to help me flash both units.

I did not know how to check the hex file since nothing is mentioned in the instructions that came with the unit. And I did not correlate that checking the hex file was the same thing as the Get slave version selection in the file menu of the F/IC6 software program on my computer. I followed the instructions to Get slave version and found that the hex file on both units was z107.hex and not z110.hex that is needed for my Miata!

I then followed the AEM video instructions on how to re-flash the units with the correct file. Presto! No stumble when I ran the latest calibration file Ken had sent me. The wrong hex file had been my problem all along!

While the guys at AEM support did know how to use and program their unit, they did not help me fix this problem. We discussed the hex file, but they apparently do not know how important that verifying the use of the correct hex file is to the successful use of their product.

I hope AEM will consider including more information in the F/IC6 written instructions about how to flash the units with the correct file for each brand vehicle and how to verify the hex file by using the Get slave version menu selection. That sure would have saved me from chasing rabbits for the last seven months.

Thanks Ken Hill! I would have given up without his help. Ken is definitely an expert for tuning with the AEM F/IC6.

Now we can try changing the M45 nose pulley and increasing boost. Hopefully, we can get another pound or two of boost without having to resort to an intercooler for the M45.

Update 07/21/2016

The new pulley has been on the supercharger for a while now. Since Ken Hill helped me to fix the stumbling problem, I have been waiting until hot weather to try to fine tune the FIC. With the 90+ degree heat starting in June, I have been adjusting the tune.

I have made many logs and have gotten the tune to work well in the heat. However, I am concerned that I have gotten it too rich for winter driving.

I plan to work on it more as I have time.

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