You guys have to remember that you will never get everyone to see that the PSD is so much better. I see what you are all getting at here but I have always had great respect for the Dodges and have yet to be let down by one. Doesn't mean I will never own or like a Ford just means that Dodges are what I prefer and there are alot more guys like me out there. The Dodge/Cummins just works for me. I do have to say that this thread is actually getting pretty educational for me now though, good work.

 

johns diesel
I am surprised. You are the one that started this and then came in and repeated that this is an engine thread. MI keeps using inappropriate comparisons when explaining different horsepower, torque, rpm properties. Short form, only when using all engine data, no gearing, no mine can go faster,etc.......
The formulas when applied simply to the engines and their powerbands, you agree that the 325-560 is more powerful???? Please explain.

 

The torque curve for the PSD is broader than the Cummins. This leads to faster acceleration. Even if they both had the same automatic transmission the PSD would still beat the Cummins for this very reason. When the Cummins is falling flat on its face the PSD still has several hundred RPM left.

What if an engine made 400 HP at 1000 RPM, but after 2000 RPM dropped off quickly? Would you still say it was more powerful over the range of the engine? Over the entire power curve the PSD outperforms the Cummins. If you want to race around a parking lot, the Cummins will give you the slight advantage.

If you can't take a logical conversation please feel free to take your posts over to a Dodge website. It's obvious that some of you are only hear to stir things up. You know who you are.

 

I'm glad it works for you. Why are you on a Ford enthusiast website?????

 

I own 4 or 5 fords, deal with other peoples Fords every weekend etc. My buddy and I tuff truck them so we know them pretty well. Built one from a frame in a weekend and it drives better then his restored chev.

 

For Mr. Spencer: Some more explanation.

325 HP at 3300 rpm

• 325HP = Torque x 3300rpm/5252
• Torque = (325HP x 5252)/3300 RPM = 517 ft-lbs
• Work for one minute = Torque x rpm x 6.28 radians/min
• Work for one minute = 517 ft-lbs x 3300 rpm x 6.28 rad/min = 10.72M ft-lbs of potential work in that minute

325 HP at 2900 rpm

• 325HP = Torque x 2900rpm/5252
• Torque = (325HP x 5252)/2900 RPM = 589 ft-lbs
• Work for one minute = Torque x rpm x 6.28 radians/min
• Work for one minute = 589 ft-lbs x 2900 rpm x 6.28 rad/min = 10.72M ft-lbs of potential work in that minute

However ....
To actually deliver the same work from each of these engines, the gearing would have to be different for each one, but yet making the wheel RPM identical. But Ford & PSD have different gears. So let’s look at that:

PSD is going 3300 rpm, which is about 90mph.
90 mile/hr x 5280 feet/mile x 1hr/60min = 7920 feet/min
The work 10.72M ft-lb / 7920 feet = a load of 1353 lbs

Cummins is going 2900 rpm, which is about 80mph.
80 mile/hr x 5280 feet/mile x 1hr/60min = 7040 feet/min
The work 10.72M ft-lb / 7040 feet = a load of 1522lbs

So, thus, what we see is that the Ford carried less (1353 lbs of resistance) but took it further (7920 feet). The Dodge carried more (1522 lbs of resistance) but took it less distance (7040 feet).

To most people, this will cause confusion and arguments. Which is better? They did equal amounts of work, didn't they. If I were to suggest to you that we go load different loads on each vehicle, and measure how fast that they go different distances, to see who really produces more work … most readers of the magazine would scratch their heads. Heck. You guys aren’t sure what to do with that information. Besides, looking at any ONE POINT IN TIME does not give us much value, either. We MUST examine a more practical scenario, ESPECIALLY involving same speeds and same loads. May the best man win. This is what the independent magazines do. Only they can't add loads on trucks starting at some particular speed. They do the simplest type of test, which is start from zero and go all out.

However, I gave you a scenario, in which BOTH trucks MUST MAINTAIN the same ground speed. This is more practical for understanding the bigger picture of overall performance. Since it's difficult to run that test, you must do it by analysis. We start with the speed, but giving Dodge all the advantage … at 1600 engine RPM (max torque). We let them run side-by-side, and add loads onto both, until the one with less torque reserve is forced to downshift. What we see is that the Ford has the advantage by selecting an engine design which has it’s horsepower at a higher RPM. It must downshift FIRST … sure. But it outlasts the Cummins. Ford made a choice: Ford would rather take a downshift … but out-endure the Cummins for hauling loads.

What would that mean, using all the math in this post above?

OPTION-A: Start with the PSD at 3300 engine rpm (325 horses) and compare it with the Cummins at 3300 engine rpm. The Cummins will have less horsepower
OPTION-A2: Start with the PSD at 3300 rpm, compute the ground speed, and then make the Cummins go that ground speed and see it’s horsepower there. This amounts to comparing the differences in their top gear ratio, and the Cummins would have to be going a little above 3300. (0.73/0.712 x 3300 = 3383 rpm). The Cummins has EVEN LESS horses there.

So, we see from Option A and A2 that having your horses at a higher RPM, either way, is a big big advantage. If you make the other guy come up to your level ... you have him beat.

OPTION-B: Start with the Cummins at 2900 engine rpm, and go through what I have shown above. Now, at 2900 engine RPM the PSD will have less power, yes. But … as I have shown in my scenario, we will get into a down-shifting game, and the PSD comes out on top.
OPTION-B2: this is actually the scenario I gave you, in which the ground speed itself is held the same. Dodge loses that one.

No matter how you toss the engineering analysis ... the PSD comes out on top. With Cummins you get one nice thing: You don't have to downshift as soon once you get a big load or hit a hill. But eventually your truck will peter out, and the PSD will pass you going over Pike's peak. Or a little hill with a heavy load, either way.

Does that help any?

Mr. Ironman

 

Oh. P.S. what is "pounds of resistance"?

That is the true load being pulled for the work you are expending. How does this relate to GCVW? Well ... there are three things involved. (A) the wind resistance of the truck and trailer will give you some amount of "pounds of resistance". The more aerodynamic ... the better. (B) the entire weight of the truck and trailer (maybe 30K or more) is multiplied times a fraction called the coefficient of friction. I.e. 30K lbs times 1% would be 300 lbs of resistance. To get this any better, you must use things like stiffer tires, better bearings, etc. Finally, (C) there are internal frictions in the gearing and engine. The torque your engine puts out at idle is JUST enough torque to overcome this internal friction.

So "pounds of resistance" is not the same as GCVW. Estimating GCVW takes into account all of the above, plus the internal strength of your truck-frame-parts to keep from falling apart mechanically as well.

GCVW numbers are often given by the manufacturers based on what they calculate they will have to repair for warranty, and have practically NO engineering basis for them. Yeah, sure, there's some general ballpark. But if you run your tires stiff, throw on anti-sway bars, avoid hills, grease your bearings, and use a very aerodynamic shield on your tow trailer .... you can easily get WAY above GCVW.

Has anyone ever seen the guy who pulls that locomotive with his teeth? Imagine what your PSD or Cummins can do.

Has anyone ever seen that advertisement where a Cummins tows this big yellow dump truck? Remember the guy who pulled the locomotive. Cough and mutter "BS" under your breath. That is an example in which Dodge is being technically truthful (yes, of course it can pull that truck) but is SHAMMING you, whipping out the snake-oil and attempting to convince you of more than what is really there. If the bearings were greased well enough (extremely low friction) ... you could walk over, lean against that truck and get it moving. Now stopping it would be something else entirely involving conservation of momentum and MV = MV.

Class is over. Go back to your Dodges, ladies.

The Marine Ironman

 

Keep this going.. but keep it nice and clean....

 

And Ford and even GM never advertise this way right Ironman?

 

MI
You're right, my brain hurts. The speeds I think 80 dodge and 90 ford are not the same although you still make the dodge going 80 miles slower the same amount of work potential. Hmmm, you did it again. Not to mention the extra wind resistance. How about slowing down the ford a little or speeding up the dodge.
Now just to answer as if it was a serious comparison, the dodge in A is well above its powerband and I believe its already been defueled, not a good comparison. A2, since we are using hypothetical gears here, if the ford was going 3300 at whatever speed, and in an effort to match resistance, the dodge should be allowed to go the same speed, which would just be a taller gear. In that scenario since load is the same and you now agree that 325hp=10.72ft/lbs, if the ford was at 325hp then the dodge would be. I think.
In B which you have allowed the dodge to operate in its powerband and its going 2900rpm, if the ford downshifted and was now going 3300 and both under full power then equals again, right. Option B2 yeah 90mph is faster than 80mph, however it still is not the same speed or load or ft/lb of work.
Did I miss something? I know that the real trucks rarely match up gears to make these comparisons easily compared, but at high hp and work, gearing to put the beasts at the same load, then what.

 

In very simple terms(which is what I need) the Ford can pull less amounts faster and the Dodge can pull more amounts slower at peak torque performance rpms. Reference Logical Heretics bolt illustration a couple pages back. I prefer to have my acceleration ability with a very heavy load from 0-40 in which the Cummins beats the PSD(autos). Once you get the load moving you don't need as much power to keep it rolling until you get to hills. The PSD has better towing acceleration ability from 40-90 mph which will dominate on hills if you are already going 55-75. The Cummins won't make it up as fast but still chugs along just fine. If you have to stop on a steep hill then start going again--- Cummins will be better(which doesn't happen a whole lot but there is tons of construction going on in Alaska every year). So from 0-40 mph the PSD chugs along just fine the Cummins does faster. From 40-90 mph the Cummins chugs along just fine the PSD does faster. No superior or inferior gearing here just the purpose the engineers designed them for.

The PSD does the 1 mile 6% grade race faster. Does that mean its a superior engine... not neccessarily. Does that mean its a superior transmission... not neccessarily. It most likely IS a superior transmission but not because of gearing... its just meant for a different purpose and so far has shown better quality even though some may think the Dodge auto's bad rep is not well-founded. It definitely is a superior engine to the people here but to say something is better because its faster is very asinine in my opinion. A 2003 SVT Cobra is faster than a 2003 Lotus Esprit... better engine?? not by a long shot. Better engineering?? no. Faster does not equal better quality people.

 

Mr. Spencer. That's what I did. That is the basis for the scenario I laid out. I slowed down the Ford. Not only that ... I slowed it down to Dodge's sweet spot ... an engine RPM of 1600rpm.

At that point, both trucks in the rest of the scenario maintain that same speed (a transaxle speed of 2192 rpm). We keep dropping heavy weights in the trailer. Because their gearing is different, they downshift at differnent point in time. But ... eventually the Dodge runs out. It's horsepower is just at too low of an RPM to keep having more weight thrown in the back. The PSD can better handle more weight tossed in the back.

So which one does more work? To say they both have 325HP is misleading. From that view, yes, potentially they have the same work output (seen as different speeds w/ different loads to make them equal to each other).

However ... you MUST examine scenarios in which the vehicles are doing something which is truly apples-to-apples. I.e.:

(a) both start from zero w/ same load and drag race
(b) both start at same speeds and keep adding weights (my scenario)
(c) both undergo same crash tests or braking tests

Things like that. You can think of more, I'm sure. System Engineers, like myself, sit around imagining scenarios, and doing analysis to see the outcome. Based on that, we learn more about the decisions we NEED to make, such as, for example:

1- no it's not worth an extra $1,000 production cost to add 20 ft-lbs of torque at 1000 rpm
2 - yes it is worth an extra $325 production cost to beef up the brakes

or strategic decisions:
1- yes, it's worth $200 million in investments to re-tool the production line and design an all-new engine and trany
2- no, it's not worth customer satisfaction and impact on sales to put an inline-6 in our light-duty trucks. Customers would rather let an auto shift earlier ... but tow more

Mr. Ironman

 

A medium duty truck is geared for towing. Im pretty sure the PSD would smoke any medium duty truck made. Even if the medium made way more hp.
He is right you know. At all rpms below 2900 the cummins makes more hp. So any throttle position besides wide open the cummins should by all means have the advantage.

 

The Cummins is not geared in the Dodge as a medium duty engine, it's geared for a light duty truck. Also, the 6.0 PSD is still offered in the F450-750, although I'd take a CAT if I were buying a F650/750. This has been my point all along. The 5.9 Cummins is a good medium duty engine, but the light duty application is not the best because the transmission doesn't allow it to stay in the sweet spot of the torque curve long enough compared to other light duty trucks. I also doubt a 6.0 PSD with a 3.73 gear ratio would outpull a medium duty truck with a 4.88 gear ratio towing more than the GCWR of the F350.

Anyway, Dodge does not treat the 5.9 Cummins like a medium duty engine, they treat it like a light duty engine and don't mate it to a good transmission. The PSD will still out accelerate the Cummins with less weight. It may rev a few hundred RPM higher, but it will do it.

Can't
Understand
Most
Meaningful
Information
Needed
Sometimes

 

John I was just showing that a blanket statement like that might not apply. You can gear one to have a higher top end or be faster. Or you can gear one to tow better at highway speeds or in the back 40. The cummins with the auto has better torque at the wheels and hp on tap at cruising speed. It is geared to tow more weight. More comfortably at 65mph. It has more hp on tap at that rpm and more torque at the wheels. This makes it slower in a race too.

Just curious MI. I see your line of thought in the last two pages and it is sound. Where did you get 80mph vs 90mph? We can compare auto vs auto now. I was just making a point previously about the 6 speed manual being a good combo for the cummins. Although not such a good choice for the 6.0.

If I can get both trucks to go 90mph. Arent they doing the same amount of work? In fact where the 6.0 has the higher top speed but it limited electronically. You can get an auto equipped cummins with 4.11s up to 96 mph which is faster out of the box than the PSD. In this scenario the roles of lb ft and per minute are reversed. The cummins is geared to pull more weight while at speed. It has more torque at the wheels in OD and direct. So while it has a lower top speed in each gear. It can tow more weight slower. Still matching the output of the PSD. 16500 2ft in 1 minute vs 33000 1ft in 1 minute. Same output. More in one hand less in the other. The cummins is geared to tow heavier. As I pointed out. Drop the OD gear to .624 for the cummins auto and you have exactly the same output.

I did the math for direct drive for both. Those 400 rpms means an extra 100 wheel revolutions. Thats pretty good. At the expense of torque at the wheels. If they have identical torque at the wheels. Geared for the same output. Then they will travel at exactly the same speed carrying the same load. As it is the PSD is geared to tow less faster. If you hooked both to a 30k lb trailer. The dodge would perform better at highway speeds.

" nobody sits in bob doles chair "