Cat vs Powerstroke torque curves
I drew out what I expect the Powerstroke torque curve would look like relative to a Cat C11. I think it is very interesting how these curves reveal the different pulling characteristics of ...
Forum Discussion
Sport45 wrote:
In a way it's like comparing golfers to baseball batters.
The golfer's swing is pretty much constant. So he chooses the correct club to send the ball downrange the distance he wants. This is similar to an industrial diesel engine with its relatively small rpm range. You choose the gear to let you do what you need.
The batter always chooses the same bat and adjusts his swing to put the ball where he wants it to go. This is similar to the gas engine which can run in just about any gear from 1500 to 4500+ rpm.
To move a load up a hill at X mph takes Y hp. If the engine can't produce the horsepower it really doesn't matter what its peak torque is.
It's actually fairly simple to calculate what that y horsepower is. For hills less than about 10% grades you simply multiply your speed x the weight of your truck and trailer x the % grade of the hill and divide it by 28125 then add the horsepower required to travel down a level road at that same speed. (100 hp is a pretty good average kind of figure for pulling a typical trailer down the level road at 60 mph). So to pull a 30000 pound truck and trailer up the 8% grade of the Eisenhower pass at 40 mph would take about 40x30000x8/28125+100 or 441 HP. Assuming the tires on the truck are 31 inches tall, the torque on the rear axle would be about 4000 lbft. It wouldn't matter if that torque was being applied by a 2.4 liter formula 1 race engine running 18000 rpm or a 16 liter Cummins running 1400 rpm. Either engine would do it so long as it had the proper gears to transmit the power through.
Edit: the formula I came up with for power required to pull a hill assumes a 25% loss of power in the drivetrain. After thinking more about that I think that is likely too high. Assuming 20% loss would mean multiplying mph x % grade of the hill x weight of truck and trailer in lbs then dividing it all by the nice round number of 30,000 and add the power required to pull your trailer on level ground at the speed your going up the hill......so add somewhere between 70 and 100 horsepower.
