Excellent posts ironman. Yes very fair. I did a little more math a few posts back. Could you go look at my wheel rpm and see if its fair.

 

Mr. Spencer. No. This is not a surprise. At those two points, each engine has the same horsepower. By definition, that means that the Torque at that point times the RPM at that point, divided by 2pi is going to come out the same.

What I have demonstrated, though, in our little scenario is that there is more to the picture than this. At equal horsepower points, they have the same work-potential, true. But they can never be going the same ground-speed if they are both at their 325 horsepower points. When the Ford & Dodge are both cruising at Dodge's max HP point ... the Ford will have much more room to reach further up and get more rpms and power. When the Ford & Dodge are both cruising at the Ford's max HP point ... the Dodge will be on it's last breath, and already unable to keep up.

In the scenario, about the time Ford downshifted to 3rd gear, the Ford engine rpm was 3371 rpm ... almost SMACK in the middle of it's strongest point! After that, the dodge has to downshift next ... and next ... and is never able to keep up. The Dodge runs out of steam.

Get this: It is physically impossible to get both those trucks to drive side-by-side at the same speed and have both at 325 HP. Impossible. Cannot be done. If you drive where the Dodge is 325horses .... the PSD has room to reach in for more. If you drive where the PSD has 325 horses ... the Dodge is on it's last leg, and fading fast.

It is this concept ... this principle ... that impelled me to make such statements as "the PSD will beat the Cummins all the time, any place, any where, any speed, and will out-tow, out-acclerate and out-speed it's opponent. The true competitor is the GMC-Duramax".

What all this amounts to is this. The Cummins is good mainly for one thing: It will save you from downshifting from 5th to 4th gear in heavy loads at a point where the PSD will have to shift. That's all. That's what your low-end torque gets you. It saves you about one downshift, maybe two. But the PSD will be right there, like a little Yorkshire Terrier, running it's little heart out ... but don't understimate that PSD for one second. It will out-endure that Cummins. The Cummins will eventually redline ... and fall back gasping for power. The PSD will cruise off into the sunset, seeking a higher tow-load before it meets it's end.

Hope that helps our understanding.

Sincerely,
The Ironman

 

I believe this is incorrect. You can gear them to go exactly the same speed at their respective peak hps. Just a tweak in either direction will net identical wheel speed.
I get about 96 mph at peak hp for the cummins with a 4.1 rearend and the auto transmission. About 105 for the PSD. You can get the cummins to exactly match the speed and torque at the wheels if you change the od ration from .69 to .624. Because they make identical hp. At peak hp if they are traveling the same speed then they will also put identical torque to the wheels via gearing. Just the way multiplying torque works. Same speed. Same output. So MI. It can be done. You can get two trucks with two different peaks to travel at exactly the same speed with exactly the same output. In fact this is more or less what they design the transmissions to do.


If the ts is governed at 90 it would actully be wise to change the gearing to produce max speed closer to 90. As it is it can travel at 90 without being at 3300 rpm. By my simple calcs it should be at about 2800 rpm when it hits the speed limiter. I higher gear would give you more torque at the wheels and give you more useable rpms in OD. Not that it matters just thinking out loud.

A quick example for torque at the wheels. In first with a manual there can be as much as 14000lb ft ot twisting force at the tire. Excluding losses. It is possible to tow 100k lbs in first, traction willing. Of course your max speed will be 10mph but it is possible. Could you tow 100k lbs in fourth. Hell no. There is only 2400 lb ft twisting that axle now and there is no way in hell that you are going to move that much weight. This is why torque at the wheels is so important. The more torque at the wheels the more weight you can move. Or the better you will be able to hold your speed when going up a steep grade. Its all about the torque at the wheels. The more hp you have. The more torque you can deliver to the wheels. Wether it be high rpm torque or low rpm torque. Its all about the hp. More torque means more hp. More torque means heavier loads. They both make identical hp but at different rpms. You just have to gear them accordingly and it is possible to get identical torque at the wheels. From both engines.

 

IRONMAN: horsepower is not work. horsepower is work over time.

IRONMAN: If both have 1hp, the one that has it at a higher rpm will either move it faster ... or move more at the same speed.

IRONMAN: The PSD/TS has less torque reserve, it appears to me, in direct drive, and will likely downshift first. This is because the Cummins has 600 ... and the PSD only 560. LESSON LEARNED: more torque wins the who-downshifts-first game. Horsepower at higher RPM wins the who-can-outtow-and-outlast game.

IRONMAN: No. That is purely a gearing choice and design. No one has "more torque" because you are always driving around under-utilizing your torque in any gear.

IRONMAN: Exactly! I assume you mean the 48RE here. In top gear, and at same engine RPM the 48RE has a 0.69 gear ratio, and it will go faster than either the PSD or Cummins/NV5600. Don't go TOO far down this path, Heretic. Guess what. You might discover that the 48RE ... assuming its a durable transmission .... is BETTER for the Cummins engine. Why don't you see if you can run our salt-flat scenario in a NV5600 vs. 48RE mode. Who will win? (I'll put my money on the 48RE). Have I trained the padawans enough to run that scenario on your own? If not, let me know, and I'll do it ... or at least double check it. I haven't thought this particular scenario through, but it's a fascinating one, given that the engines themselves are idential in HP, torque and max RPM. My first back-of-the-paper-napkin analysis says a 0.69 might give you more than a 0.73, and the manual is doomed to not keep up. (autos are better for towing .... autos are better for towing ... assuming they don't break).

IRONMAN: Yep. That ole TorqShift must be looking better by the minute to you. Listen. I'm telling ya. Ford put a real engineering marvel on the road with that TorqShift. It outshines the PSD in my opinion, and the PSD is awesome itself. You truly have the "dynamic duo" in those two. Duramax/Allison ... eat your heart out.

IRONMAN: Yeah ... but that ain't the whole picture, as I'm sure you're now beginning to see. It has more low-end torque, remember? But the PSD will outlast the Cummins, because it has "further reach" to coin a phrase.

Sincerely,
The Ironman

 

Bigsnag, you're missing out. Report for duty w/ Mr. Heretic and Mr. Spencer. Those ladies have worked their way up to boys, and you don't want to be falling behind.

IRONMAN

 

Horspower is work. Force over time. Work is force over time. Not work over time. Cause you aint doin work without time.

 

IRONMAN: Yes ... you could ... certainly. But that is not what has been done in this case. I mean that given the NV5600 and the TS ... they can never go the same ground speed and both be at 325 horses.

IRONMAN: Yep. We're in violent agreement.

IRONMAN: Yep. Hand salute. I agree.

 

It would seem so. But this isnt how it works. They both can move 33000lbs 1 foot in one minute. No faster no slower. Otherwise it wouldnt be a hp. The one that makes 1 hp at 10000 doesnt have enough torque to move the load without a much lower gear. So you have to give it a 100 to 1 gear instead of a 10 to 1 that the 1000 rpm motor will need. You must multiply the torque for the 10000 just to move it. Otherwise no work will be done.

 

Teacher correct me if I'm wrong. If we are in od we are using only .71 to 1 for the TC and the NV5600 .73 to 1. In other words, niether engine is using it full potential. If you change the the NV to .69 it would have to down shift sooner as we raise the hill. Correct?

Once out of OD we are back to 1 to 1 and 3300 still beats 2900. Correct?

 

Tmyers. Im sorry. I have been doing some math for the autos to get a better idea what type of rear wheel speed we are talking about.

You must be in a good mood MI. This has been a good discussion today.

In fifth yeah. When it comes time to work the only gear it uses that further reach is when the cummins downshift to second. Auto vs auto. The TSshould by my est. should give up fifth easily. It doesnt have enough torque at the wheel to hold this gear going up a good hill. So it immediately will give up the gear that gave it its further reach. If the dodge stays out of 2nd. It will have a further reach because of the higher wheel speed. If the dodge does wind up in second. It is going about 3 mph slower than a TS will in third. 45.5 compared to 48.8. All assuming rpm from peak hp for simplicity. That is a very steep hill to pull a 325hp diesel down to 45 or 48mph. Maybe 12%.

I dont think the different multipliers will make an auto better or worse for towing. Its about the driveability. The ability to keep the engine in its sweet spot. To choose the correct gear using you noggin. Which by my est is smarter than the computer choosing the gear cause you get to see the road ahead. It does not have this information. If you are towing very very heavy. Its all about gear spacing. 6 is better than 5. Or for dodges case 4.

 

IRONMAN: I don't quite follow you. Let me try again, perhaps we are in agreement:

Work, for an engine, uses two things: Torque (a force measured in ft-lbs, which misleadingly is the same units as for linear work), and distance, which in this case is measured in radians that have been revolved through. 2 pi's of radians make a whole circle. The radians are unitless ... and the outcome is still ft-lbs ... but a much higher number, and now officially "work". You call the one "foot-pounds of torque" and the other "foot-pounds of work".

Power, is work over time (or force times velocity). The units are ft-lbs divided by time (seconds usually). Horsepower is synonymous, and can be converted to ft-lbs/sec. Thus ... Horsepower is torque times radians divided by time (or torque times velocity). A "quickie" formula is HP = (torque x RPM)/5252. The time snuck in with the RPM ... the "per minutes" that is, which is same as "per seconds" but divided by 60.

You're saying that "Work is force over time. Not work over time. Cause you aint doin work without time." ... is a bit odd. Work has no units of time. Work is also energy, which we have not discussed. Time is not necessary for energy. Although, this alludes to some interesting quantum level physics.

I believe that time, space and matter are all necessarily inter-twined, and so from that view NOTHING exists outside of time. Time is a part of the fabric of all of physical creation. Time must have a creator or an author, one who exists outside of time. In fact, a creator of time could prove his existence by telling people within time of future events in a predictive mannor, and only the one existant outside of time would have that knowledge or information.

Care for that conversation?

The Ironman

 

IRONMAN: Yes, but you forget one thing. If two engines each have inherently 1hp ... but that comes inherently at different engine rpms ... then the engine with 1 hp at the higher rpm can do more work.

 

Terry, yes, if you are geared at 0.69, you are very likely going to have to downshift first, all else equal. If you have a 1-million ft-lbs of torque engine behind that 0.69 though ... you may still have more reserve torque left, and NOT need to downshift, either. It can go either way. What's more important is the reserve torque and work-potential of that torque.

On the second point, if two engines both drop to 1:1 gear, and assuming have enough reserve torque to handle a load at that point, then of course the higher RPM will go faster. Key, again, though is reserve torque.

 

IRONMAN: Agreed. However, once the PSD downshifts, it will keep reaching up in RPM. And that's a game against which an inline will almost assuredly lose. The PSD, having downshifted, is now "ahead" in torque-reserve. The inline will downshift next. This will keep going back and forth at different times. Eventually the torque-margin gained by the inline will be less and less. The torque-margin at each shift of the V8 PSD will be more and more. FInally the inline will redline .... and deadline.

IRONMAN: Now that, I agree with. Some of my very first posts pointed out this inherent weakness with the 48RE. More gears is always better.

 

Hp is representave of how much work an engine can do. force distance time. It will not exceed this. 33000lb 1 ft in one minute. No matter the rpm. If its 100 rpm or 100,000 rpm. They are going to lift the 33000 weight 1 ft in 1 minute. Of course the 100,000 rpm engine will need to be geared down a bit but the effect is the same. 33000lbs 1 ft in 1 minute. The 100 rpm one obviously makes a lot more force so it would not need as short of a gear. Imagine like a 1 speed bicycle gear ratio compared to a gear the size of a dime turning a gear the size of a backhoe tire. That little dime size gear is really cruising. But you could stop it with your fingers, assuming you would not get burned due to friction. Not much force. It would be much harder to stop the 100 rpm engine. Much more force. But look at the bright side. It wouldnt burn you. Both will only do 1 hp worth of work. No more no less.

In a vehicle there is something else at work because you are using a multigeared transmission. Still if more work was being accomplished it would have more hp. The force is 517 lbs applied at 3300 rpm. This is 325hp. The cummins makes more force but uses less rpms. To accomplish the same amount of work. 325 of those 33000 lbs 1 ft in 1 minute. The work is the same. What is different is the gear you would use to accomplish the work. Gotta love that high rpm torque for racing.

I did the math and the 48re will travel further in first and second than the TS will. Its geared that way. Taller gears. Direct and od will obviously not.