Cat vs Powerstroke torque curves

06Fargo wrote:
There is a FLT Ike video where a Volvo class 8 running empty with a grocery van blows the doors off the pickup and gooseneck flat deck FLT is testing up near the top. My guess is the semi weighs around 28 to 30000 lbs - close weight to the Big Pickup and its trailer. I'm not finding the clip to link just yet...

I remember that one .

Sport45 wrote:
That Volvo could have had up to 600hp. That would easily blow the doors of of any of the pickups they may have been testing.

Volvo D16 Spec Sheet

For some reason when you see the curves for diesel pickup engines torque is shown on the major (left) scale. For OTR and industrial engines it seems HP is most often seen on the primary axis. Go figure...

That is majorly due to the fact that with pickups, you mainly only have one transmission choice(accept for Ram 3500 diesels) per engine, and maybe three or four rear gear choices so it is crucial to get as much torque from the engine as you can.

With the big trucks, your transmission selection list is just about endless allowing you to get anything from from a 10-speed all the way up to an 18-speed. Even two of the same speed transmission can have different gear ratios in each gear. That combined with the long list of rear gear options(the popular Eaton 404 starts at 2.64:1 and ends at 7.17:1) makes torque output not that important of an issue since you can spec the truck out to virtually put as much torque to the ground as you want with gearing. Since you cannot multiply horsepower with your gearing spec, it becomes the advertised factor between the engine competition.

That Volvo could have had up to 600hp. That would easily blow the doors of of any of the pickups they may have been testing.

Volvo D16 Spec Sheet

For some reason when you see the curves for diesel pickup engines torque is shown on the major (left) scale. For OTR and industrial engines it seems HP is most often seen on the primary axis. Go figure...

There is a FLT Ike video where a Volvo class 8 running empty with a grocery van blows the doors off the pickup and gooseneck flat deck FLT is testing up near the top. My guess is the semi weighs around 28 to 30000 lbs - close weight to the Big Pickup and its trailer. I'm not finding the clip to link just yet...

It's interesting to note that in my above example a 4.10 rear axle still wouldn't deliver the necessary torque to stay in third so the truck would still downshift to second and only be going 31 mph at 3000 rpm. It would only be using 314 of its rated 440 hp.

A truck/trailer on the Eisenhower pass at 8% grade and 30,000 lbs combined weight and 33" tall tires will need to put 4450 ftlbs of torque on the rear axle to maintain a speed of 40 mph. If the engine has enough power and the drivetrain can deliver more torque than that to the axle the truck will speed up. If the engine/drivetrain are not able to deliver the 4450 lbft of torque the unit will slow down. Slowing down will not change the torque requirement much......to maintain even a slow crawl will still require about 4200 lb ft of torque.

I'm going to say the 2016 Powestroke can put 85% of its torque to the rear axle. At 2800 rpm that equates to about 700 lbft and at 1800 rpm it works out to 731.
So to get to 4450 it needs a 6.36 gear reduction. If the truck is equipped with a 3.73 rear axle it would require a 1.70 gear reduction from the transmission. Unfortunately that gear is not there. The transmission would have to drop to second gear where it gets 2.32 gear reduction. Now it has more than enough torque but in second gear revved to 3000 rpm the Powerstroke can only turn the axle 347 rpm. The truck is only capable of 34 miles per hour. To turn the axle 347 rpm while delivering the required 4450 lbft of torque only requires 294 Hp at the rear axle so 345 flywheel Horsepower. That is about what the Cat C11 makes over a broad rpm range so without doing the math I'm pretty confident that the 335 Hp Cat would almost keep up to the 440 hp Powerstroke.

It's likely that it wouldn't keep up on many hills but if you knew the truck/trailer weight and all the gear ratios you could calculate the grade where the Powerstroke would win.

06Fargo wrote:
I heard there is a movement that is gaining momentum to replace 450HP 12 and 15 litre 84,000lbs GCW linehaul engines with 440HP Power Strokes now that torque doesn't matter. Big weight savings to be had...

That would be great if they could last a million miles hauling 80k, but good luck with that. Big rig engines make high torque because they have to. They are built with big, heavy components that simply can't withstand higher RPM but are needed to handle the nearly 100% duty cycle they see. Without RPM, you have no HP unless you jack up the torque.

Engine weight doesn't really matter at 80k.

06Fargo wrote:

As far as 6.7 PS vs Caterpillar C13 - if a guy swapped a 440 PS/auto trans into a class 8, and removed a 430hp / 1650 C13 - and re-geared the diffs to allow the PS to howl at it's max output, that should be a fair comparison... hooked up to the same trailer on the same grade... if "hp is hp" it should haul 80,000lbs up the grade exactly the same as the measly 1650 oops sorry 430HP Cat ...

I believe you're absolutely right.

The FLT guys talk about "holding full throttle unless the speed limit is reached, let the engine and trans do it's thing..." during their runs.
Didn't the 6.4 gas engine derate itself to hold in a gear rather than scream to the governor then upshift then lug down then downshift then scream to the governor then upshift and lug down then scream to the governor?

I heard there is a movement that is gaining momentum to replace 450HP 12 and 15 litre 84,000lbs GCW linehaul engines with 440HP Power Strokes now that torque doesn't matter. Big weight savings to be had...