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These ECU's work a little different than previous Fords.
They are Torque based and use 'Torque Based Decel'. IE, you program the torque to be used on Decel and the ECU closes the Throttle to achieve the Torque (or negative torque) on decel. If it has determined that it's not enough, it retards ignition timing. It is 100% normal to see negative ignition timing on decel. Even on the stock and track key tunes. It may not be severely retarded on the first decel, but as the ECU learns, it starts to retard more and more ignition timing. We do not have control over what timing the ECU learns to use on Decel, and the programmed Torque on decel in my tunes is Ford Factory Stock. I use TiVCT changes to increase compression braking. (Which could accentuate the decel popping, but I have not tested that theory.)
The Popping on decel is directly related to your exhaust system. The un-burnt fuel (due to severely retarded ignition timing) exiting the engine on decel can mix with fresh incoming air from the tailpipe creating a perfect mixture to burn. A little heat from the exhaust system and you get popping on decel (backfires). The larger the exhaust, the worse it can be. Exhaust leaks and cut-outs can also greatly increase this affect.
There is 1 thing we can do in the tune, but it will result in decreased compression braking and will likely not solve the decel popping completely. Plus I do not know what other effects it may have as I have not tested it myself. A tuner buddy told me about the change and said it cured the decel popping on a few customers cars.
They are Torque based and use 'Torque Based Decel'. IE, you program the torque to be used on Decel and the ECU closes the Throttle to achieve the Torque (or negative torque) on decel. If it has determined that it's not enough, it retards ignition timing. It is 100% normal to see negative ignition timing on decel. Even on the stock and track key tunes. It may not be severely retarded on the first decel, but as the ECU learns, it starts to retard more and more ignition timing. We do not have control over what timing the ECU learns to use on Decel, and the programmed Torque on decel in my tunes is Ford Factory Stock. I use TiVCT changes to increase compression braking. (Which could accentuate the decel popping, but I have not tested that theory.)
The Popping on decel is directly related to your exhaust system. The un-burnt fuel (due to severely retarded ignition timing) exiting the engine on decel can mix with fresh incoming air from the tailpipe creating a perfect mixture to burn. A little heat from the exhaust system and you get popping on decel (backfires). The larger the exhaust, the worse it can be. Exhaust leaks and cut-outs can also greatly increase this affect.
There is 1 thing we can do in the tune, but it will result in decreased compression braking and will likely not solve the decel popping completely. Plus I do not know what other effects it may have as I have not tested it myself. A tuner buddy told me about the change and said it cured the decel popping on a few customers cars.