Unexpected open loop

[guru1oftal]

I am data logging a stock 2017 5.7 Ram and noticed that it goes into open loop/Accel every time RPM reaches 4,300 even though the pedal is a volt below the PE threshold (2.5V or 50%) and coolant temperature is well above the thresholds for closed loop operation (199F). I have verified that timing moves from PT to WOT when this happens.

Has anyone seen this before and any reason why it happens?

[rockystock]

I am data logging a stock 2017 5.7 Ram and noticed that it goes into open loop/Accel every time RPM reaches 4,300 even though the pedal is a volt below the PE threshold (2.5V or 50%) and coolant temperature is well above the thresholds for closed loop operation (199F). I have verified that timing moves from PT to WOT when this happens.

Has anyone seen this before and any reason why it happens?

Might be your catalytic convertor overtemperature protection kicking in, it will start adding fuel to cool down the cats. Log your Cat temps. I also created a math to calculate the amount of fuel-air being added beyond the stoich amount. At stoich or commanded afr=14.7, the value is zero. When at WOT or COT, the value goes up and shows up on my graph. Makes it easy to find all the WOT and COT spots in a large log file. I think you could also log your commanded AFR; it will drop steadily to a minimum and rise back up to 14.7, inverse to the "fuel-air adder."

If it's your COT adding fuel, you will typically see a gradual increase in fuel-air to a peak, and then a similar decrease back down to zero as the convertors cool down below the threshold temp. I've found with my stockish tune that COT often adds significantly more fuel than at WOT.

[guru1oftal]

Might be your catalytic convertor overtemperature protection kicking in, it will start adding fuel to cool down the cats. Log your Cat temps. I also created a math to calculate the amount of fuel-air being added beyond the stoich amount. At stoich or commanded afr=14.7, the value is zero. When at WOT or COT, the value goes up and shows up on my graph. Makes it easy to find all the WOT and COT spots in a large log file. I think you could also log your commanded AFR; it will drop steadily to a minimum and rise back up to 14.7, inverse to the "fuel-air adder."

If it's your COT adding fuel, you will typically see a gradual increase in fuel-air to a peak, and then a similar decrease back down to zero as the convertors cool down below the threshold temp. I've found with my stockish tune that COT often adds significantly more fuel than at WOT.

Thanks for the input, I'll definitely check out COT. I hadn't considered that possibility since both commanded AFR and timing are changing when this happens.

[rockystock]

Yeah your timing will also change - the PCM will shift over to the WOT Thermal spark table while in COT. You can log aircharge and spark timing, and make a table in VCM scanner using the axis labels of the WOT thermal table. Plot the spark timing in that table (filter the spark timing by something like "commanded AFR <14.7") and you'll see the timing roughly match the table in your tune.

[f.creek-ranch]

I miss the answer for it....
The RAM has a short runner valve in the intake wich will activate at this rpm range.
Maybe it this operation wich uses only WOT ???