Dieselsmoker: Cummins torque curve, more torque than PSD at all rpms below 3000, etc.
IRONMAN: Well, sure. The Cummins is rated for 600 ft-lbs. Why wouldn't it be higher? At least at 1600 rpms. Above and below that ... well ... possibly. Then again maybe not. Edge products's curve is not a real one.

CLASS FOR ALL: Okay. I looked further down and saw Heretics bulb is actually beginning to flicker on (he said "weird" to the fact that the PSD has more work at it's power max, even though 325 is the same, and he reminds me the fastest truck in the world is a low-revving inline 6). Okay ... let me explain. There is another phenomona that I've never seen addressed on this forum by anyone, which is a key to this whole deal, and also explains why I am always dubious about any so-call "dyno" curves:FORD/DODGE: The transmission selected for an engine represents the final decision that engineers have made on trading "what to do" with reserve torque needed above overcoming wheel friction. You can use it all up by gearing it for high speed. Or, you can "save" it by gearing for low speed, and be able to maintain RPM when a load is dropped in back.

WORK ACCOMPLISHED: If an engine only ever turned at one set RPM, we could compare PSD and Cummins very easily. For instance ... let's have each going at it's max HP: 325/2900 and 325/3300. The PSD can produce more work. If you loaded each equally, the PSD could keep more weight being tossed on it, because 325x3300 is a higher number. But in reality, the engines are reving up and down the RPM curve due to the dynamics of moving, stopping, acceleration and so on. So ... you need to look at ALL the rpms and multiply them times ALL the torques all the way from IDLE ... to maxed-out top end. And guess what. The engine with the broadest RPM range will win ... EVERY TIME. Everytime, folks. Laws of Physics. All it's torques times all it's RPMs simply comes out to a bigger number EVEN IF it's average torque is lower the whole way. It will either (a) be geared to go faster or (b) be geared to allow towing a bigger load.

SUMMARY: Since the PSD gives 325hp at 3300 rpm, and falls off later ... it's total area under the torque curve is more .... therefore ... it can produce more work (total integrated torque times total integrated rpms).

Long enough post for now. Absorb that for a bit.

MARINE IRONMAN

 

Hmm. Interesting. Entertaining even, but wrong. Also, it doesnt win everytime. Only when it has an auto. The PSD makes less force. Faster. It can push with less force longer. If you were to load em down like a dog sled competition til they could hardly even move. The one that exerts more force will be the winner. The one with more torque. Assuming you couldnt rev up the rpms and didnt have a torque multiplier.

It comes down to the stuck bolt. The bolt that needs 600lb ft of twisting force to break loose. Not 560. If you dont have enough force to break the bolt loose. Then you did not accomplish any work. At the end of the day. Torque rules. Now if this bolt had 3300 threads. And it required no more than 560lb ft of torque to unscrew. Then hell yeah. Your styling. Cause the other guy is stronger. Can exert more force on that bolt. But he can only spin it 2900 times in a minute and you can unscrew it 3300 times in a minute so your going to get that bolt out first. Poor sap. Lost to a weaker man. Cause he wasnt as fast. Stronger but slower. Kinda like a powerlifter. Compared to a bodybuilder. Your strong but hes stronger. You can lift the weights slightly faster but he can lift more.

HP is work. So many pounds so many feet in so much time. The PSD is rated to do EXACTLY the same amount of work in the same amoung ot time over the same amount of distance. It cannot do more work because it has more rpms. Otherwise it would have more hp. It actually moves less weight faster if you like my example above. IT CANNOT MOVE AS MUCH WEIGHT. But it does it faster. Ignoring gearing clutches and torque converters.
Example. I can lift 50lbs up 10 ft in 1 minute. My best friend is stronger but slower. He can lift a 100 pounds up 10 ft in 2 minute. Who did more work?

The more rpms will allow the PSD one advantage. Gearing. It can hold a gear for longer. It can accelerate in first out to 3300 where the cummins has to shift to second at 2900. BTW. The cummins should by all means get to 2900 first. If both were at full throttle at max boost producing max hp and torque. Even though the cummins is in second and the psd is in first. They both still make 325hp. But the PSD has more torque at the wheels because it hasnt had to shift to the lower multiplier yet. Thats why its faster. Not because it does more work. Because it gets to hold the higher multiplier for a split second longer in each gear. Effectively traveling further while accelerating slightly faster for a split second. Every time you shift you accelerate slower. It may not feel like it. But thats the way it is. Are you making less hp. Heck no. Just have less torque at the wheels. You trade acceleration for distance. Each shift.
Quick example. The cummins is rapped out in 4th at 2900 going up a steep grade. Giving it all it has. The PSD can do the same grade in third and maintain the same speed. It requires more rpms but itll do the same speed. This is an example. I have no idea where either are at in those gears or what speed they would be traveling. The ability to use a lower gear and rev higher will help you maintain speed. When it is very steep and you are heavily loaded.

Everybody elses dyno is fake except for yours. If you notice. All the fake ones are consistent. Just like all the fake tests that put the manual cummins out in front I guess.
Lets do some hp math. You seem to have a hard time admitting the cummins makes more hp at all rpms below 2900.
This is flywheel assuming max hp and torque. In other words its what they can produce if they need to. +or- 5hp
Cummins PSD
1500=164 1500=142
2000=228.5 2000=213.25
2500=281.3 2500=259.5
2900=325 2900=300
3300=na 3300=325
More torque equals more hp. Across the entire powerband it has a 15-25hp advantage. More work. At lower rpms. The PSD needs to use more rpms to do the same thing. If the cummins needs 2100 rpm to hold its speed up a 7% grade. Then the PSD will need slightly more rpms. Just to do the same thing. It will also need to be coupled to a shorter gear if it wishes to carry the same load. Cause remember. It moves less weight faster. So you would have to gear it to move more weight slower.

This is the difference between a diesel and a gas engine. The diesel can drag a full load up the mountain at 2500 rpms whereas a gas engine would need 4500 rpms and a lower gear. Just to go the same speed. Why? Thats where the torque dictates it needs to be. Not saying the PSD would need a lower gear. They have are within 20 hp of each other. But it would need more rpms just to do the same thing. If you were to put em both in direct drive and drive em up against the governer. The PSD would travel farther. Higher rpms. But would need a slightly lighter load. Unless you regeared to carry the same load. In which case both trucks would be moving at exactly the same speed.

 

Thought about it. Need more information. I have been listening to this constant higher rpms at max hp and more area under the curve stuff and the observation that this is what determines the winner. First question: determines what? I can see your point that if 325 pulls more at 3300 than at 2900, you have more absolute power to pull....maximum load requiring maximum power to maintain speed. However once you move downwards from there, first......how much difference in torque at each point would determine a winner, winner being defined at equal loads and equal time which one would be further down the road. Some time being spent by one vehicle 2900-3300 in a place which the other could not go(with power), the rest of the time being spent below 2900 rpms. What I believe you are saying is that simply because you can go higher, you go further down the road? In real world wouldn't you need to factor in for each vehicle time spent at each rpm and factor that into your analysis? Since both vehicles at some point start at idle, no motion and go through a series of ups and down on rpm load hp tq whatever, the time spent at each rpm would seem to show a clearer evaluation of the engines with reference to its application. Both vehicles start of low rpms revving up to max then up and down until the comparison is done. Each vehicle goes up in first lets say under full throttle to shift at max power, then repeat the process as they shift and go up and down in rpms. However does it make sense that each would probably spend more time lower at rpms than higher? At lower rpms the power is not as great so the acceleration of the vehicle would take longer. So the time spent to get higher would increase hence more time at lower rpms in each gear? I believe the stronger engine would not just be the one that has a higher power at max rpm or has more area under the curve but the one utilizing more power for more time could. That is why the ps using the torqueshift can beat the cummins using the dodge auto but I would guess that if a test was done rigging the 4sp auto to both or the 5sp auto would at the very least make the acceleration tests closer if not possibly making the dodge a winner. Remember, the 4sp auto vs 5sp auto at 13k+ lbs towing was only won by two trucklengths. And if the 6 was coupled to the 4sp and the 5.9 to the 5sp.? An interesting comparison for this debate but one I'm sure we'll never see.
There are all the road tests that seem to confirm this. If you consider the dodge and the ford with its current lastest and greatest only the ford wins all tests done with the autos. Dodge with the manuals. As far as the engine alone, the dodge seems to be stronger yet coupled with the auto the ford can still beat it. With the engines going max rpms under max loads the ford can outpull the dodge.
Am I thinking right?

 

Guys, I'm not going to even take the time to read through every single word... I've skimmed this, and I just want to put things in perspective for us all: we're a bunch of guys arguing over the internet about the effectiveness of various powertrain combinations, and drag racing 7000 lb trucks, no less. This is silly. Let's not kill each other. Especially because the closest we can come to scientific explanations about what we're trying to say depends on "estimations", i.e. torque converter and clutch efficiencies.

We're all right, and we're all wrong. MI, it's obvious to me that you'd have nothing but an auto PSD for towing. That's great, and it's the right combination for you. A lot of people prefer manuals. I don't think either camp will ever prove to the other that they are right, and there is no point. They both perform fairly similarly. If we're looking at two Ford trucks, and the auto version produces more starting torque, good. I'll still take the manual. I don't have to have the best numbers -this isn't a (SNIP) contest- I just prefer manuals. They are simple as dirt, and inherently efficient. New autos are great and reliable, and they may last a long time, but there's still more that COULD go wrong. I'm not saying it will, just that it could, and I don't want that in a truck. Plus, when clutch replacement, or even rebuild time comes, I can do it myself with a MT. I would think that, as an engineer, you could appreciate a desire for simplicity.

If you bring me similar trucks, one with a manual, one with an auto, and you race the auto with me driving the manual, I guarantee you won't walk away. May win, I dunno. I'm not talking crap, I just think some people have no concept of how well a manual can be driven, even a HD one. My best friend has a 75 F250 Highboy with a NP435 - basically the beefiest manual ever made. Is it clunky? Yes, but I can knock off a 3-4 shift passing someone on the highway that will knock your head against the back window. The best example of bad manual trans driving can be seen on any given day in a town where riced-out civics are popular.... Since they put 4" and 5" fart cannons on those cars, everyone for blocks around can hear the rpms go up to about 3000 every time they take off, before dropping back down to the proper road rpm. I have never understood this. When I teach people how to drive stick, one of the things I always emphasize is that the more you rev the engine up, the greater the mismatch between the speed of your drive wheels and the speed of the flywheel, and thus, the more clutch wear, and the longer it takes to get going. A good stick driver will proportionally apply gas as the clutch is released, never letting the rpms get much above or below idle until the clutch is fully engaged. I can have this done, pulling into traffic, in a fraction of a second. The only real exception is when you're pulling such a heavy load that you have to keep it from bogging out, in which case, yeah, a little slipping of the clutch is required. Even then, though, it's not as bad of a thing as people make it out to be, if the driver has the sense to get the clutch fully engaged ASAP. Even in workhorse farm trucks, I've never seen a clutch go bad until after 100,000 miles.

I have nothing against a PSD, but I can't afford one. Or a Cummins for that matter. In any case, Dodge trucks are junk. The only reason I've ever jumped into any of this stuff is in certain cases where I'm skimming through and there was an argument of fallacy being made. I just think we should try to stay objective. I'm a poor-a$$ 21 year old college kid. If I were going to buy a semi-late model truck, it would be a SD with a 5.4 and manual trans. Not a 325 hp/500+ ft-lb powerhouse, I know, but it would be tough and reliable, and would pull a boat and do assorted misc farm work quite well.

 

Okay, time for class number 2. Potty break is over, ladies. We will now walk through an engineering analysis of why the total area under the torque curve is SO VITALLY IMPORTANT. Imagine Dodge and Ford driving across the salt flats w/ a tow-trailer. We are going to start at Dodge’s max torque point of 1600 engine rpm. The trailers are empty. In my math, I will only show the transaxle rpm (assume rear end and wheels all the same) and will use RPM instead of radians. Here goes the analysis:

(1) Dodge work potential is 600 ft-lb x 1600rpm = 960K ft-lb, transaxle rpm = 1600 / .73 = 2192 rpm

Ford must go transaxle of 2192 rpm, so engine turns 2192 * .712 (5th gear) = 1560 rpm, Torque @ 1560 rpm = 515, work potential of the Ford = 515 ft-lb x 1560rpm = 803K ft-lbs.

The Dodge has more torque reserve (i.e. the ever-wonderful low-end torque, 960 to 803). God magically drops a load in each trailer, and it’s maxed to 803K ft-lbs of load. The Ford must downshift.

(2) Ford downshifts, must maintain transaxle rpm = 2192rpm, 4th gear is 1.0 so engine is going 2192rpm Torque @ 2192 rpm = 555 ft-lbs. Work = 2192rpm x 555 ft-lb = 1,217K ft-lbs.

Now ford has more torque reserve (1217 to 960. God magically drops more load in the trailer and the load is upped to 960K and Cummins must downshift.

(3) Dodge downshifts, must maintain transaxle rpm = 2192 rpm. 5th gear is 1.0, so engine is going 2192 rpm. Torque @ 2192 = 585 ft-lbs. Work capacity = 2192rpm x 585 ft-lb = 1,282K ft-lb.

Now dodge has more torque reserve (1282 to 1217) but the margin narrows. God, once again, adds more weight and the load is upped to 1,217K ft-lb and Ford must downshift.

(4) Ford downshifts, must maintain transaxle rpm = 2192 rpm. 3rd gear is 1.538, so engine is going 2192 rpm x 1.538 = 3371 rpm. Torque @ 3371 = 520 ft-lbs. Work capacity = 3371rpm x 520 ft-lb = 1,753K ft-lb

Now Ford has more torque reserve (1,753 to 1,282). Notice when dodge gets ahead the margin is narrower. Now when Ford downshifts the margin is larger. This spells doom for doge. God adds more weight and the load upped to 1,282K ft-lb and dodge must downshift.

(5) Dodge downshifts, must maintain transaxle rpm = 2192 rpm. 4th gear is 1.39, so engine is going 2192rpm x 1.39 = 3046 rpm. This is substantially beyond peak horsepower, and there is at least a 15% loss from max torque down to 510 ft-lbs. Work capacity = 3046 rpm x 510 = 1,553K ft-lb.

Ford STILL retains more torque reserve (1,753 to 1,553). The dodge is now in a position of never being able to catch up. The race is soon over. God adds yet more weight again, and the load is upped to 1553K and dodge must downshift again.

(6) Dodge downshifts, must maintain transaxle rpm = 2192rpm. 3rd gear is 2.04, so engine is going 2192 x 2.04 = 4471 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 1,553 in the trailer.

Thus … the Ford will ALWAYS out-tow a Dodge Cummins. If you keep upping the trailer load, the Ford will always downshift first, because the Dodge does have higher low-end torque. However, eventually, you will load the trailer heavier enough so that the Dodge runs out of rpms in the down-shift game. It will reach a point where the Dodge MUST slow down, while the Ford maintains speed.

Marine Ironman

 

Now that I've posted my class #2, I've gone back and read the three previous posts. You are all full of hot air, and mostly don't know what you are talking about. My post just above this one, goes step-by-step through what happens. You can double-check my math, but I think it will generally stand. Otherwise ... this is why engineering schools are selective, and pre-requisites must be learned each step of the way. Some people ... apparently ... just are incapable of going beyond a certain point.

IN summary, The actual work output of an engine is it's torque (a force) times it's rpm. The units still come out in ft-lbs. So ... 600 x 1600 will never amount to more than 560 x 2000. Period. End of Story.

From the un-educated point of view, Dodge has 600 ft-lbs, it's 40 more than Ford, and so Ford can never tow as much as a Dodge. Bask in your ignorance. Enjoy the simpleton life, and good luck to you.

MARINE IRONMAN

 

No it weighs 4700lb and it was stump puller. We just thought it would be fun to take to the drag strip.

This whole site is about is having fun and sharing info. This is what we are doing. If you don't find this fun my suggestion would be ingore this tread.

LH, The Dakota with the cummins may be the Fastest Truck in the World but only because a) Gale Banks had the money to build a custom chassis, they are just using a Dakota body b) Gale Banks wanted to show case what you could do with a diesel, he picked the Cummins. Don't think for a minute that someone else can't come along and best his speed and it will probably be done with a gas engine.

And don't even start in on the gas vs diesel debate. When you can break the tires loose with out shifting at freeway speeds come talk to me.

Back to the topic at hand though. It is safe to assume that the engines sitting on the dyno the the Cummins has the most torque. Hook both engines up to identical trucks, same trannys and gues what the Cummins still has the most torque so it can still get the move a larger load. It did this though at the sacrafice of speed, by moving the power curve down the RPM range.

Let use the TS and set it up to ensure we will never shift in to the next gear and drop below pick torque.

Dodge

1st - idle to 2200 - 16mph
2nd - 1600 to 2250 - 23mph
3rd - 1600 to 2300 - 33mph
4rd - 1600 to 2500 - 51mph
5th - 1600 to 2900 - 92mph(peak HP)

Ford

1st - idle to 2800 - 20mph
2nd - 2000 to 2800 - 29mph
3rd - 2000 to 2800 - 41mph
4th - 2000 to 3050 - 63mph
5th - 2000 to 3300 - 104(peak HP)


P.S. I think MI said it way better than I did.

 

Your maximum towing on the excursion I believe is 11k lbs. At what weight below 1101 lbs would a dodge 600 not tow a load? The max combined weight is still low enough to pull most any load, but you forgot to add how much god loaded us down with. Lets see, the powerstroke going 3371 or 71 rpm is still climbing in hp? You give it 520tq which equates to 334 hp. New numbers. Actually hp is falling at stated rpm and tq going even farther down.
Dodge tq at 2192 rpms is 585? We know at 1600 its 600 and at 2900 its 588. Where did you get the dip? Another phantom.
Again you give different gear ratios so we have gotten away from comparing engines to powertrain.
On and on. Dodge redlines well before 4400 rpm I think. Would just not downshift but slow down. The Ford as well could not maintain speed at 3300 and 325 anymore than the dodge at 2900 and 325. To keep even the Ford would just have to be geared lower.
You say that 1600@600 will never beat 2000@560. Yes, but 2000@560 took longer to get there than 1600@600, and if 1600@600 kept accellerating to 2000, it would be somewhere in the range of 595or so. But now you can explain how 560 got there at the same time or how instead of comparing 2000rpm vs 2000rpm you gave diff. rpm and different torques. Come to think of yeah, at all torques below 2900rpms, give comparative data, it still comes out to ..... should I say it.......325-600 beats 325-560
Not hard to figure really.

 

Marine Ironman: Is that God adding more weight example supposed to simulate hills? because that is a horrible illustration. Very unrealistic. A load is a fixed weight. If the Ford PSD-auto and the Dodge Cummins start a race towing the same amount of weight or no weight at all the PSD is going to win every race farther than 1000 ft. be it 10 miles 20 miles or 30 miles. THIS IS TRUE. So everyone that needs to tow something dangerously fast to their destination or if you like to hot-rod diesels and don't plan on modifying... the PSD is for you . If you tow very heavy, prefer low-end torque and like to have that little bit of leeway that your truck isn't loaded down to the max... the Cummins is for you . If the PSD has any extra area under its torque curve it is very, very slight. It does however have more area under its HP curve. What the PSD does have... is more torque and hp to the wheels at 2900-3300 rpm which is why it wins that 30 mile race because as Ironman so kindly pointed out to us if something does the same amount of work at a higher RPM... it goes a farther distance. If something does the same amount of work at a lower RPM, it tows more effectively. Take your pick.

 

It seems that slight advantage under the torque curve along with the superior automatic transmission results in the Cummins bewing the inferior choice in all situations whether towing to the max or as a daily driver.

 

tmyers
nice description, but what would happen if you used numbers for the transmission that would reflect max power. Instead of using 1600 and 2000, try 2900 and 3300. I don't drive an auto so I don't know where they would shift but I assume near max power under max throttle?
Also what engine w/ts accelerate faster in each gear?
Remember the ps has a governor and can only go 90something in speed anyway? With time factored in just listing estimated hp at beginning and ending, overal time to get to a distant point would favor who?

 

I agree. No matter how slight the advantage is, the advantage will still make it a better engine. And that's just torque. A big advantage in the HP curve area just adds to it. Taken from DD last post.

 

An engine is an engine. A transmission is a transmission. Truck is also a truck. I haven't read where anyone is comparing the total automatic powertraing ford vs dodge with the dodge superior. Some have defended the complaints about dodge trannies breaking as not wellfounded. I don't recall if anyone has said the auto dodge vs auto ford with same load and rearend would give dodge the advantage. No direct comparison has yet, however what we have been comparing is the engine.

Seems like we keep going in circles. And all over a fairly slight performance difference between trucks. hmmmm.

 

The governer is there as far as I know on all Ford trucks except the Lightning. For this discussion though pretend its not there. Its easy to defeat anyway.

Take it to 2900 and 3300 would hurt the Dodge even more. Why you are that much farther away from peak torque, but 'll show it anyway.

Dodge

1st - idle to 2900 - 21mph
2nd - 2100 to 2900 - 30mph
3rd - 2050 to 2900 - 42mph
4rd - 2050 to 2900 - 62mph
5th - 1950 to 2900 - 92mph(peak HP)

Ford

1st - idle to 3300 - 24mph
2nd - 2300 to 3300 - 34mph
3rd - 2300 to 3300 - 48mph
4th - 2350 to 3300 - 68mph
5th - 2150 to 3300 - 104(peak HP)

Hwy speed(70) = 2200

Dodge(6sp manual just for fun)
1st - idle to 2900 - 12mph
2nd - 1800 to 2900 - 19mph
3rd - 1700 to 2900 - 33mph
4rd - 1950 to 2900 - 47mph
5th - 2100 to 2900 - 65mph
6th - 2100 to 2900 - 89mph(peak HP)

Hwy speed(70) = 2250

As you can see looking at the same trannys on the differnet engines with the the shift points suggested by dsp the Cummins is anywhere from 350 to 500rpms above its peak torque while the Ford is 150 to 300. We really won't talk about the manual. I just put that up there for fun.

Lets look at the power band here. For the Dodge, 1600-2900, Ford 2000-3300. Both 1300 rpms. But where do we live running highway speeds, 2200 rpms. To run these speeds the Dodge as already used 50% of the power band while the Ford has used only 15%. At speed the Ford has more power available. I think this is what MI means we he says under the curve.

The Dodge traded speed for lowend power. This may work well on the farm but out on the highways I think this shows the Ford to be better.

 

Whoa - that's all I was saying, and I know I exaggerated the weight - I'm just saying that we all should take a step back and relax for a minute. I'm not by any means insulting anyone... I'll race anything... I've got a 210 John Deere at home that the governer spring broke on, so it has a direct connection to the throttle linkage... been that way for 10 years, and hasn't flown apart yet... I'd race it against any garden tractor you have - just an example.