Yeah the city bus that I was trying to ride on today died, and guess what??? It was the Cummins B's turbo that died--no injector, no leak, just the turbo died--no whine from it at all. The good news it that they are changing to Cat engines now.

 

RE-posted w/ some of my typos corrected:

PSD/TS vs CUMMINS/48RE

A Ford PSD/Auto-TS and a Dodge Cummins/Auto-48RE are driving across the salt-flats. They each have an empty trailer into which we are going to add weights until someone must downshift to maintain speed. They both must also maintain the same speed. The first forced to slow down loses the race. We will start with the most ideal speed for the Dodge, which is 1600 engine rpm (max torque of 600 ft-lbs). Each has a 4.10 rear axle, the best for towing and 31inch diameters tires on a 16-inch wheel. Therefore the speed they are running at is: (1600 rpm x 3.14 x 31 inches) / (0.69 x 4.1 x 1056) = 52 mph, which is a nice comfortable highway speed.

(1) DROP IN THE FIRST LOAD (827): Ford must downshift to 4th

Dodge work potential is 600 ft-lb x 1600rpm = 960K ft-lb(6.28rad/min), transmission axle rpm = 1600 / .69 = 2319 rpm

Ford must go transmission axle of 2319 rpm, so engine turns 2319 * .712 (5th gear) = 1651 rpm, Torque @ 1651 rpm = 530 ft-lbs, work potential of the Ford = 530 ft-lb x 1560rpm = 827K ft-lbs(6.28rad/min).

The Dodge has more torque reserve (i.e. the ever-wonderful low-end torque, 960 to 827). We drop a load in each trailer, and it’s maxed to 827K ft-lbs(6.28rad/min) of load. The Ford must downshift.

Ford downshifts, must maintain transmission axle rpm = 2319rpm, 4th gear is 1.0 so engine is going 2319rpm Torque @ 2319 rpm = 550 ft-lbs. Work = 2319rpm x 550 ft-lb = 1,275K ft-lbs.

(2) 2nd DROP OF MORE LOAD (960): Dodge must downshift to 3rd

Now ford has more torque reserve (1,275 to 960 ft-lbs (x6.28rad/min). We drop more load in the trailer and the load is upped to 960K ft-lbs (6.28rad/min) and Cummins must downshift.

Dodge downshifts, must maintain transmission axle rpm = 2319 rpm. 3rd gear is 1.0, so engine is going 2319 rpm. Torque @ 2319 = 585 ft-lbs. Work capacity = 2319rpm x 585 ft-lb = 1,357K ft-lb (6.28rad/min)

(3) 3rd DROP OF MORE LOAD (1,275): Ford must downshift to 3rd

Now dodge has more torque reserve (1,357 to 1,275 ft-lbs (6.28rad/min)) but the margin narrows. We once again add more weight and the load is upped to 1,275K ft-lb and Ford must downshift.

Ford downshifts, must maintain transmission axle rpm = 2319 rpm. 3rd gear is 1.538, so engine is going 2319 rpm x 1.538 = 3567 rpm. Torque @ 3567 = 450 ft-lbs. Work capacity = 3567rpm x 450 ft-lb = 1,605K ft-lb(6.28rad/min)

(4) 4th DROP OF MORE LOAD (1,357): Dodge must downshift to 2nd

Now Ford has more torque reserve (1,605 to 1,357 ft-lbs x 6.28rad/min). We add more weight and the load upped to 1,357K ft-lb and dodge must downshift.

Dodge downshifts, must maintain transmission axle rpm = 2319 rpm. 2nd gear is 1.45, so engine is going 2319rpm x 1.45 = 3363 rpm. This is substantially beyond peak horsepower, and there is at least a 25% loss from max torque down to 450 ft-lbs (if not lower). Work capacity = 3363 rpm x 450 = 1,513K ft-lbs x 6.28rad/min.

(5) 5th DROP OF MORE LOAD (1,513): Dodge must downshift to 1st

Ford STILL retains more torque reserve (1,605 to 1,513 ft-lbs x 6.28rad/min). The dodge is now in a position of never being able to catch up. The race is soon over. Yet more weight again, and the load is upped to 1513K and dodge must downshift again.

Dodge downshifts, must maintain transmission axle rpm = 2319rpm. 1st gear is 2.45, so engine is going 2319 x 2.45 = 5681 rpm. REDLINE. Cannot maintain that engine rpm… the truck is forced to slow down to a slower transaxle speed, and go slower with the new load of 1,513 ft-lbs x 6.28rad/min in the trailer. So what should the Dodge slow down too? Well, if the max RPM for the dodge is about 3500 rpm, then 1,513 ft-lbs x 6.28rad/min divided by 3500 rpm means it would need a torque of 432 ft-lbs. Can a Dodge produce that amount there? We’ll assume so. The new speed of the Dodge will now be:

Speed (mph) = (3500 RPM x 3.14 x 31 inch tires) / (2.45 x 4.1 x 1056) = 32 mph[/QUOTE]

 

52mph in 3rd for the TS is above peak hp. Torque is falling off. It cannot travel 52mph in second nohow. In other words. Your not likely to hold 52mph with any kind of load behind the PSD. Let alone the dodge. You cannot hold that speed. The dodge will do it in third but not second. The PSD will have a hard time in third and cannot in second. Its above both engines torque curves out of direct. In direct. The cummins has the advantage.

You are correct though. if the dodge drops into second. The PSD will eat it for breakfast. Top speed wise. But in second the cummins could tow more of gods weight than the PSD can in third. More torque at the wheels. I get 45 mph at max hp in second. The PSD should do about 48 at peak hp in third. Dodge could move more weight at this rpm and hp though. If both were going 48 mph at peak hp. They could move identical weight at identical speeds. With identical torque at the wheels. Identiacl hp at the flywheel. They are just geared to do different things at different velocities.

My only problem with that math is that what load would it take to pull these trucks down into first. It would be 4 times their legal rated load. So In first. The PSD has more torque but has less top speed. Same with second. It appears like you said the doge would drop into first while the PSD retains third. There is no scenario where this is possible. You are the engineer. How much weight would it require to need that much torque at the wheels. My guess was about 90k lbs. There is almost three times more force at the wheels in first than in direct for the dodge. If it can tow 16500 in direct up a 4% grade. Do you multiply by a factor of three to discover gods weights up a 4%. I have no idea how much hp is necessary to overcome friction and wind resistance. I know these trucks will do over a 100 without a load. So there is a lot of hp left over at cruising speed empty.

The PSD has more torque in first but less maximum wheel speed. If you lock both into first and drive to redline the dodge will be traveling faster. The second gear of dodge is slightly slower than the third gear of ford. Again lock both in second drive em both to redline the dodge will be traveling faster. Less torque at the wheels equals higher velocity. Thats the way multipliers work. The are capable of identical velocity and torque at the wheels. If geared properly. Its the way gears rpm and hp work together.

Now if you compare both in direct and OD. The two gears you will use the most while towing on the highway. The dodge has more torque at the wheels. Same work. More, but slower. BTW. I would not tow with either below 2000 rpm. Peak torque for the PSD. 600 x 2000 and 560 x 2000. Except the psd is geared to be at 2050 at 65mph. So 600 x 2000 and 560 x 2050. This is where they are going to do most of their work. Not the most work just most of their work. Both will do 325hp worth or work. One is geared to pull better at highway speeds. Actually the PSD is geared well to travel at 70mph in direct drive. About 75 would be peak hp. The cummins is not geared as well. It will be at peak hp at 65mph. Though the dodge has more hp available at this rpm and more torque at the wheels in this gear.

If you needed to hold 65 to pull a big hill. It would do that quite well. Better than the PSD trying to hold 65 to pull the same hill. I have done the math before and i dont think the PSD could hold 75mph at 6%. So on a 6% or greater the cummins has better gearing. This in my mind is the true test of an engine. Not a race from a dead stop up a hill. I like to hit the hill with a little momentum. Im not likely to line up at the bottom of a big hill on the highway. Stop. And race. Im gonna hit that thing runnin. In this scenario. The dodge at gross is more likely to hold its speed. Once again. Ive never had to downshift to second in any vehicle on the highway so I dont think its pertinent to actual rear world towing. I cannot imagine any scenario that would pull a 325hp diesel into second on anything short of a 12% at gross.

If both were towing 90k. The PSD would have a gearing advantage in first and second. I may be mistaken. It may only be 40 or 50k but its well beyond what you or I would tow. Me with my idi and you with you modern marvel.
It is an unrealistic comparison.

 

Heretic, in real world towing the Dodge wiil kick down into second, second gear is passing gear on them, you start slowing down on hill and put yer foot into it and it will hit second. I assume that Fords tow/haul mode locks OD out right? I know that in the '02 ram my buddy has it says to lock OD out while towing.

 

Most autos will lock out OD. I dont know if the TS is immune. Second has a top speed of maybe 50 mph with 4.11s. You arent suppose to tow in OD with a manual either. Its too much load for the engine. Tends to lug. Luggin kills motors. If you are doing 65 up a hill and floor it is in the gear it needs to make max hp and sufficient torque at the wheels to do the job at that speed. It is unlikely to kick down into second unless you have a taller rear end.

Plus an auto in 02 doesnt have 325hp and 600 lb ft of force resisting deceleration on a big hill. Stick an ez cranked all the way up on the same truck and you will have similar results to a 600. Depending on the rear diff of course. With 420lb ft of torque and a 3.55 rear end. It can and will grab second if needed. A 600 lb ft cummins with a 4.11 will have slightly more torque at the wheels in third than a 420 lb ft with 3.55s will in second gear. got me.

 

Tow haul does not lock out overdrive on the torqueshift.

 

Very interesting. What is the recomendation in the owners manual?

 

For what???

 

Proper gear for towing. When I read my owners manual for my previous na 7.3 it said not to use od. I thought this was standard on manuals or automatics. Its to keep from lugging. At least thats what I thought it was for.

 

Well with the tow-haul it might not go into OD depending on the load but it will upshift if it is able. T/H more or less gives you torque converter lock in thru the gears.

 

From what Ive read the tow haul locks the converter in second and third in addition to od for the 48re.

 

I believe mine will do it from 1st thru 4th

 

That was my understanding too.

 

I was thinking about your comparison some more MI. Direct would be a good gear to compare. Instead of saying ft lbs a minute why dont we just call it hp. Something that everyone is familiar with. At peak hp. In direct. The cummins will tow more weight slower. The PSD will tow less weight faster. Same with OD. That pretty much sums it up.
Why? The cummins makes more force with less distance. The PSD makes less force with more distance. In the end they will both do 1,760,000 ft lbs of work per minute. One has more torque in one gear the other another. One has higher top speed in a gear the other another. It appears the cummins will be faster to 30mph and the PSD to 60. If they are both loaded near gross. If you want to race with a diesel the PSD is definitely the correct choice. If you want more hp at the rpms you drive at everyday. The cummins is the logical choice. The torqueshift is a tiebreaker if you want an auto. The nv5600 is a tiebreaker if you want a manual. Then your onto cab choices. Towing capacities and purchase price. I would like a PSD with the cummins powerband and a torqueshift transmission. The PSD is a great engine. I prefer I6s but am not against owning any diesel made by international.

Im glad you stuck with it this was a lot of fun. I hope we can do it again on another topic. You will find I choose an underdog side and root for it. I dont really care. I just like to debate. To ask the question, Why? Someones gotta do it. I dont even like dodge.

If you wish to discuss further. Im still game. As long as its clean and its all in good fun. This stuff is a blast for me. Its a good way to kill time.

 

This stuff is a blast for me. Its a good way to kill time.


Not for those of us that have to follow it...