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MBT tuning when reflashing

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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I understand the concept of tuning for MBT when live tuning is an option and can be done on the dyno. My question is, how do you go about tuning for MBT when live tuning is not an option? An example would be using a hand held tuner such as a diablosport, where you can use the CMR software to make changes to the maps then it must be reloaded into the ecu and live tuning is not an option.

Hi Shane,

Best way to do it is with pulls on the dyno, you need to try and recreate the same conditions each time, coolant temp etc so the tests are fair

It's not possible to perform the spark sweep test that we demonstrate in the course when you can't make live changes. Fortunately in most cases the part throttle timing in a factory map is going to be at or very close to MBT and hence it's not as critical to make adjustments there. On the other hand it's very simple to make full throttle ramp runs and add timing to see the effect on torque/power. This is identical to how we dial in the timing under WOT with a standlone ECU that can be live tuned.

Is it still the case that sticking with the factory timing is sufficient for part throttle if a slightly higher octane fuel is available compared to what the vehicle is recommended to operate with?

What mods are done to the engine? If you only have simple bolt ons, the low load/cruising spark (MBT spark) shouldn't be too affected. When you change heads and/or cam(s) there could be a significant difference due to slower burn. Also, changing variable valve timing settings can also affect it. That being said, unless it's way off, you're looking at more like a minor impact on fuel economy than anything. If it's way off you could get some hesitations or misfires (if under sparked).