2021 Ram 3500 H.O.

Cummins12V98 wrote:
"I mean what’s your opinion about the Cummins that’s 370/850? I’m thinking with 4.10’s that combo will be just awesome for loads under 25k."

My 15 DRW/AISIN is a measly 385/865 and it moves my combined 35k double tow load just fine all across the West Coast. Trans nor engine ever gets hot even in 100 degree weather pulling long 6% grades.

That is a cool pic. I am not certain how the ECM determines when to defuel to keep your engine from melting down but my suspicion is that your not making 385 hp on a 100 degree day pulling a long steep grade. Shiner can probably set me straight here.

I think safe temperatures are controlled based on things like charge air temp, boost pressure, rpm and the amount of fuel being injected. (Basically EGT can be calculated without being directly measured). So it is likely that defueling occurs based on indirectly measured EGTs. Because the engine defuels on long hard pulls in hot weather the radiator is not being taxed the way it would if the engine was able to put out its full power all the way up the hill. I would be very interested in knowing what it takes to get these trucks to defuel on a long hard pull in 100 degree heat. I think when our pickups defuel it might not be that apparent ...we don’t feel a sudden power loss ... rather the power tapers off. (Im not aware of a time that my pickup defueled but then I’ve never pulled a long steep hill in 100 degree temps)

I’ve never witnessed my Peterbilt defuel on account of EGTs ... The 15 litre engine will put out 550 hp and pull like a freight train until the coolant gets hot. At 220 degrees a red light comes on but there is no reduction in power. I believe it’s 230 degrees where the engine light comes on and the power is suddenly and severely backed off till the coolant drops back down to 220. (It very seldom happens that 230 degrees is reached but 220 is fairly common)