This assumes it will keep dropping. At gross up a 7%. It will not keep dropping. It will find a gear and rpm where there is the perfect torque at the wheel. If the TS drops into third and the 48 holds third. Then the cummins would be faster. Unfortunately this scenario is unlikely and depends on other factors. Its really a matter of how much weight. There will be a weight where either will win. Like I said I dont think you can pull a 325hp diesel into second on a highway. I may be mistaken. But I dont think its likely. If the cummins holds third. Which I think likely. It will be travelling faster than the PSD if it cannot hold fourth. If there is sufficient weight to pull the cummins down into second. The PSD will eat it for breakfast. The thing is. It would have to be a lot of weight to pull the PSD out of fourth. There torque at the wheels in fourth at peak hp are 2120 to 2410. Cummins advantage. Cummins could tow more in direct but sacrifices ground speed. You could change the ratio to give them identical speed and torque. To me it seems unlikely that either would come out of direct. I havent towed heavy with either so I have no real world experience.
A good friend of mine bought a 555. Maybe I can talk him into letting me tow with it. To get a feel for it. Just like ive said all along. The PSD is faster. Even after the math. I think the cummins would be more comfortable at highway speeds. It has more torque at the wheels in direct and overdrive. Also more hp at 2000-2400. Not a lot but some. The common cruising rpms for both with the 4.10. What suprises me. Is after the math. My money would be on the PSD out of the hole. Must be cause it can hold first and second longer. I would definitely think the PSD had the advantage.

 

Ironman, I'm getting a kick out of you're referring to yourself in the third person like Bob Dole.

 

Insularism…. works quiet well for him...this thread has its own life...all others need not apply/reply

 

I usually stay out of these threads to avoid the errant slings and arrows usually present...

but this is GREAT !

working some brain muscles I haven't had to test in a LONG time with the work I do

I won't jump in until Ironman has completed his discussion with himself - quite entertaining


My first reaction was that -
Hey - it's just a truck comparison... just take it to the street and compare...

then I realized this is a great theoretical logic exercise
- brings back the old college days...


Now to the statement about time as being stated by an entity removed from time... THAT thread could take a lifetime !!!

 

Bottom line, they'll both get the job done. The PSD will make it up the hill first as Ironman was pointing out with his adding weight illustration. Maybe we'll see a closer competition when they put the 5 speed auto with the Cummins. Call me stubborn but I still prefer the Cummins even after seeing all the situatons the PSD will prevail. I feel that its the better tower. I don't care for all this superior inferior talk I think the Cummins is geared more with towing in mind. Besides I wouldn't keep mine stock anyway I would put that clutch and pusher pump in that bring my 1700 rpm torque over 1000 ft. lbs.

 

I knew there was no convincing some of you guys, even when based on fact and careful analysis.

If the Cummins was geared more for towing then it would beat the PSD in a towing comparison, which it does not.

 

Most arguments like this are pointless. PSD vs. Cummins, V10 vs. PSD, gas vs. diesel, etc. You're really never going to convince but about 10% of them.

 

John how often do you gun it the entire time while towing a 10k load to your destination? In real life it is not a race its casually towing with the common courtesy of keeping other drivers and their families safe. Which is why I assumed my die hard ford man uncle purchased a 2003 Cummins over a PSD for towing his 5th wheeler back and forth from Alaska. When I said geared more with towing in mind I meant real world towing, not racing 1 mile up a 6% grade in a magazine test.

 

That's an extreme test. If the PSD outperforms the Cummins at WOT it will certainly outperform the Cummins at lower speeds as well. Let's have a little reality check here. If one truck outtows the other with 10K it will also outtow it with 5K.

 

I guess I'm crazy but when I tow something, I usually lay it on the floor (or nearly on the floor) until I reach my cruising speed which is often 75-80 mph, since speed limits are 70-75 now. If my truck won't take it, I'll get one that can!!!!!

 

The post count is at 596 and still trying

 

Well, here's another post. First, for Heretic, you keep thinking HP of an engine is some universal number stating the total amount of work it can do. This is false. The total amount of work DEPENDS upon the RPM. The Horsepower is simply the potential to produce work at that one rpm. HP at different RPMS mean different things in terms of work output.

Your ignorance may be because I short-cutted on much math in the analogy, to quickly get to relative numbers for comparison's sake. For example, I did not convert RPMS to radians, and so forth. Here is an explanation of work and loading:

At each gear, the torque is stepped up and the RPM is stepped down (or vice versa) The product of the Torque and RPM remains the same (i.e. energy is conserved). For example, if an engine like cummins puts out 600 ft-lbs at 1600 rpm ... then ... goes through 5th gear (1.0 ratio) and then goes through a 4.0 rear differential, we then have 2400 ft-lbs being applied at 400 rpm. 400 x 2400 = 960,000 ft-lbs of work per minute. Also 600 x 1600 = 960,000 ft-lbs of work per minute. Energy is conserved. In reality there is some loss through the drive train, but energy is still conserved. It is still there in the form of heat from frictional loss.

Of course it doesn't take that amount of torque to move just an empty vehicle. If the truck is empty the actual torque output will be much less, because the load on the engine is less. Those maximum torque numbers, from engine curves, tell you what the engine MAY put out under the highest load that it can take.

EXAMPLE: What would it take to "ellicit" 600 ft-lbs of torque at 1600 rpm? It would take 960,000 ft-lbs per minute (as shown above) x 6.28 radians per revolution is 6,028,800 ft-lbs over that minute. At 1600 rpm, a Dodge/Cummins is going about 50 mph (my guess, but you can redo this with the exact number) that is about ... oh ... 4400 feet per minute. So this work does 6,028,800 ft-lbs over a minute and moves 4400 feet in that minute. Divide, and we see that the load for that was 1370 pounds. That 1370 pounds represents the TOTAL RESISTANCE of the entire vehicle to moving forward. Friction in the trailer bearins. Wind resistance. Etc. Depending on the coefficient of friction and wind loading, you can make your own guesses as to the total combined weight that can be pulled. Shape of the truck/trailer makes a big difference.

The Ironman Has Spoken
The volcano is quiet now. Go back to your trivial existences and driving of Dodges. Peace be with you.

 

Hello out there any of you have jobs? Ok the ditches are dug and I am here.

OK BS alert(am I allowed this).
MI in post #556 "your complete ignorance of engine physics than to completely ignore rpm. This has nothing to do with gearing either." You then go into engineer mode and compare 1600rpm dodge to 2000rpm ford showing the ford having more ft/lb. or work force. Then in post #562 I ask why not compare like rpms instead of using different ones. I go ahead and do the math and low and behold yes at both rpms maximizing fords torque and minimizing dodges torque, at both points it still has more ft/lbs of work. I further remember your long ago post saying the 325 can do more work at 3300 than at 2900, so go back and do the math again and low and behold. 3300 and 2900 come out the same..........
Your response is to now revert back to what......gearing again?????? If engine only is used (I don't think we need to go through all these computations with the gearing, the psd beats the dodge with autos assuming same rear end)as you have said then whats up dad?? The biggest deal is that you are a degreed engineer and this should be simple. If 1)the post from 556 does not involve gearing, why do you need gearing to explain your way out of it.......and 2)if it does involve gearing, at what gear or speed or whatever and in what vehicle are you talking about when you use the numbers 1600rpm dodge vs 2000rpm ford. It seems like you were just comparing power at these two points to me.......

BS BS BS and when compairing fairly at like rpms then work available.........325-600vs325-560 still you have no answer.

 

This is only correct if youare measuring the hp at the rear wheels. If you are going by crank ratings, then Ironman is correct, whoever uses their power more efficiently (making that hp at a higher rpm) is going to tow the same amount faster or more at the same speed.

 

Wrong! He has the right answer you just don't want to hear it. Maybe you can't hear it over the volume of the old Cummins you're remembering. Your repeated statement of flywheel numbers and no more proves that you don't have an understanding of the big picture.