Cat vs Powerstroke torque curves

The only thing a C11 and a PS have in common is burning diesel fuel.

rjstractor wrote:
The industrial or OTR diesels are also designed to run 1,000,000 miles or more at a full power duty cycle. The PSD and others could have similar duty ratings but their power ratings would be reduced, probably to half what they are in a pickup. Even in the F650 its power rating is reduced to only 330/725. Similarly, a Cummins ISB in a Freightliner M2 has a max rating of 325/750, with ratings as low as 200/520. To have a million mile full power duty rating, those engines would likely need to be limited to about that 200/520 rating.

The peak power rating of the Powerstroke might not affect its life nearly as much as you think. Many industrial machines and some highway tractors can work all day long in conditions where they require nearly 100% of their engines rated power output. The Cat engine makes its peak power of 335 hp at 2000 rpm. At the low end of it working range, 1200 rpm, it is still able to deliver 285 hp or 85% of its peak power output. Even though the Powerstroke has a max power out of 440 hp it almost never generates that kind of power. With your foot in it pulling a heavy RV you are seldom at rpms above 1900. You can see from the graph that @ 1900 rpm and full throttle the Powerstroke is only capable of making about 900 lb ft of torque which equates to 325 HP. At 1500 rpm the Powerstroke might be capable of making about 825 lbft of torque or 235 hp which is just 53% of its rated power output. Just casually cruising down the highway with a 15000 lb trailer in tow only requires about 100 hp.

The industrial or OTR diesels are also designed to run 1,000,000 miles or more at a full power duty cycle. The PSD and others could have similar duty ratings but their power ratings would be reduced, probably to half what they are in a pickup. Even in the F650 its power rating is reduced to only 330/725. Similarly, a Cummins ISB in a Freightliner M2 has a max rating of 325/750, with ratings as low as 200/520. To have a million mile full power duty rating, those engines would likely need to be limited to about that 200/520 rating.

hone eagle wrote:

4x4ord wrote:

hone eagle wrote:
Mine peaks about the same , at around 1650 ftlbs . it has never come out of overdrive.
EGR climbs a bit, boost climbs a lot and if the dash is displaying instant fuel mileage I get chest pain.

I take it you have a 485HP C13? You don't have to be much over 1300 rpm to be making 400 hp.

Volvo D12 set at 465 -500 on cruise.
Flat land running -1200rpm @65 mph - bit over 9mpg

And note the revs. Large trucks are not cruising at high revs, they are near peak torque for best fuel economy. So the torque rise theorized as the revs drop is not available in the way you mean it. There will have to be a downshift to raise the revs above peak torque before that works.

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Nice graph, 4x4ord.

The automotive type diesels probably are tuned to save their flimsy clutches, auto-transmissions, rear axles and twisty noodle frames.

Under the heading, "other observations", the torque curve difference above also well illustrates the main difference between a gasser vs diesel. I had two 3/4ton Ford trucks simultaneously, a 2000 6.8L V-10 gasser and a 2000 7.3L diesel.

On hills, the low hp (235) diesel running at 65 mph (or about 1800 rpm), was already in it's high torque rpm band at overdrive during normal highway speed. Even left in Cruise Control, it seldom shifted out of overdrive to pull our travel trailer uphill. And running without Cruise, held at steady throttle, it never shifted out of overdrive on the moderate rolling hills of I-94 in ND and usually sacrificed less than 5 mph cresting.

The gasser, which has greater hp, (310) shifts down once, or even twice, on the same hills as the engine seeks it's high rpm torque band. Frequent shifting is only moderated slightly by manually holding a steady throttle. And, to save brutal tranny wear, it is best to lift-and-shift down ahead of time, under low throttle/torque conditions, prior to the hill.

The diesel has about 500 footpounds, the gasser about 450. Offhand, the diesel did about 2 to 3 mpg better... until some lady totaled it while parked in my driveway. Sigh.

Wes
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4x4ord wrote:

hone eagle wrote:
Mine peaks about the same , at around 1650 ftlbs . it has never come out of overdrive.
EGR climbs a bit, boost climbs a lot and if the dash is displaying instant fuel mileage I get chest pain.

I take it you have a 485HP C13? You don't have to be much over 1300 rpm to be making 400 hp.

Volvo D12 set at 465 -500 on cruise.
Flat land running -1200rpm @65 mph - bit over 9mpg

hone eagle wrote:
Mine peaks about the same , at around 1650 ftlbs . it has never come out of overdrive.
EGR climbs a bit, boost climbs a lot and if the dash is displaying instant fuel mileage I get chest pain.

I take it you have a 485HP C13? You don't have to be much over 1300 rpm to be making 400 hp.

Mandalay Parr wrote:
How about the C7 curve?

The 300 HP C7 would be a flatter curve than the C11 drawn. At 2400 rpm the C7 makes about 655 lbft of torque and it rises to a peak 860 lbft as it pulls down to 1440 rpm.

Mine peaks about the same , at around 1650 ftlbs . it has never come out of overdrive.
EGR climbs a bit, boost climbs a lot and if the dash is displaying instant fuel mileage I get chest pain.

How about the C7 curve?