Forum Discussion
RoyJ
Jan 08, 2021Explorer
4x4ord wrote:
^^^^ It would be nice to see the bsfc map for the 2021 Cummins. You are right that keeping the torque high and rpm low saves fuel for the heavy trucks that pull hard all day. How or where are you seeing more gears helping the Ram pickup get better fuel economy? Where on that map would you like to see a pickup truck engine run while towing a 16k - 18k trailer down the highway?
Let's build an imaginary pickup heavy hauler. 2021 Cummins dually, 10 spd Ford transmission. We'll have to assume that bsfc map applies to the new engine, with the same torque curve, just shifted up to 1458 N-m.
235/80r17 tires turn 654 rpm @ 60 mph. Let's start with 3.31 gears, here's the rpm in each gear from 45 - 75 mph:
This is where the beauty of the 10 spd shows - at every given speed we can put the engine into the rpm where peak bsfc occurs (~1500 - 2000 rpm). 6th & 7th @ 45mph, 7th or 8th @ 50, 7th & 8th @ 55, 8th & 9th @ 60, 8th & 9th & 10th @ 65, 9th & 10th @ 70, and also 9th & 10th @ 75.
The BEST part is we have 2 to 3 gears to choose and still stay within the optimal RPM. This means we can also pick the gear depending on load to get the engine torque into the optimal range.
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