transamz9
Lawrenceburg Ky
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Hannibal wrote:The tire diameter was shorter on the mid 90's Dodge Cummins so the effective ratio would be similar to the newer ones with 3.73. The problem was not enough horsepower. even my '03 with 460 ft/lbs of torque was slower on the uphills than my '05 Hemi powered Ram with 365 ft/lbs of torque. The Hemi had almost 100 more hp.
On the uphills the Hemi could run in 2nd gear to multiply it's torque by 1.67 where the SO Cummins had to run in direct. 365 X 1.67 = 609 ft/lbs of torque at the drive shaft. The Cummins in direct was pushing it's 460 ft/lbs. Higher horsepower will always equate to more torque at the drive shaft.
transamz, why not just go read Pickuptruck.com's HD shootout? I have a job and family. Far past the age of going out playing drag race up the mountain with my pickup truck. Fact is, we tow everywhere we want to go with my gasser. The hew HO gassers and diesels both will out tow my 5.4L and my Hemi before it. I've owned several diesels. If the benefits were there, I would simply own another one. It's a pickup truck, not a miracle. I think you're making way more out of it than it is.
Here's some reading material for you from the masters of diesel engines. It's horsepower.
http://www.catrvclub.org/PDF_Docs/Understanding_Perf.pdf
If you notice in that link, the torque goes up with the hp. That has nothing to do with what we are comparing. I like to read this stuff and have studied this stuff until my head hurts. If you want to drag race two unloaded vehicles then yes I agree that the gasser will stay with the diesel with the same horsepower but when it come to "work done like towing heavy loads, the gasser will never keep it's speed unless you can hold it at it's max power. How long do you think you gas truck can run at 5,000+ rpms?
Here's some reading for you also. You can't have HP without torque.
HP verses Torque for towing
Some more good reading......
How Force, Power, Torque and Energy Work
2016 Ram 3500 Mega Cab Limited/2013 Ram 3500 SRW Cummins(sold)/2005 RAM 2500 Cummins/2011 Sandpiper 345 RET (sold) 2015 Sanibel 3601/2008 Nitro Z9 Mercury 250 PRO XS the best motor made.
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Taco
VA
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Ok lets compare the mentioned class 8 tractor with 365 horse to a pickup with 365 horsepower.
Horsepower is a function of torque and rpm. it is measurement of the amount of work that can be performed over time.
A road tractor with 365 horse would probably have it's hp peak at about 2100 rpm so for 365 horse at 2100 it would be making 913 ft lb of torque at 2100.
A gas pickup with 365 horse would have a hp peak at perhaps 5400 rpm. it would have 355 ft lb at 5400 to make 365 horse.
Torque is multiplied by the transmission. Let say for a road speed of 60 mph.
A 41 inch tall tire would have 492 revs per mile. so for 60 mph at 2100 rpm. a 3.55 rear end and a 1.20 transmission ratio. so 913 x 3.55 x 1.2 = 3889 x .768 = 2987 torque (what is .768? is the ratio of radius of 31.5 to 41 to account for the gearing difference of tires. 15.75/20.5 = .768)
A 31.5 inch high pickup tire has 640 revs per mile. so 5400 rpm with a 4.30 rear end and 1.96 tranny ratio. 355 x 4.3 x 1.96 = 2991
So the torque applied to the road from a gas pickup truck and a class 8 tractor with 365 horse is exactly the same. (they do vary a couple from rounding in ratios)
The difference is a class 8 tractor operating in a region with those kinds of hills probably has 18 speeds and tops out at 70. so it can be at it's horsepower peak ever 3.8 mph so for all intents in can always be at peak horsepower for towing applications. This is by design by the way.
A typical pickup truck is only at peak horsepower in two gears before 70 mph. So only at two road speeds is it ever at peak hp. A diesel pickup is no better. Put an 18 speed geared accordingly hooked to a gas 365 horse engine and it will tow every bit as well as the diesel road tractor. however it will use more fuel.
I have done the calcs for road torque between a lmm duramax and a new ford 6.2 and the ford gasser has more road torque at more road speeds in the 40-70 range than the diesel.
Horsepower is what matters.
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Hannibal
Tampa Bay Area
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I give you a link from the masters of diesel engines and you give me "how stuff works"? Torque is a component of horsepower. More torque gives you more hp at lower rpm. More hp gives you more torque through gear reduction. Nothing to get a headache about. If you want to know how much torque you need to run 60mph up a grade, you first have to figure how much horsepower is needed no matter what fuel you're burning. Then you have to decide what rpm you want to run. Then you can calculate how much torque is needed to produce the necessary hp at the desired rpm. But it starts with horsepower as the Cat site spells out clearly. You can't get around that. I ran my 250hp Cummins at it's peak hp 2900rpm many miles. My '98 12v Cummins with 5spd/4.10 ran at it's peak hp 2500rpm at 70 any time I was running 70mph. The 5.7L Hemi, during R&D, was run hundreds of hours at peak hp 5400rpm full load. Tear down showed only normal wear. Won't hurt a thing.
Why are you starting to tell me what I've been telling you and passing it off as your own? Torque is a component of HP. Torque without rpm is a static measurement. It implies no movement at all. Torque with rpm is known as horsepower in our application. Already been said.
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transamz9
Lawrenceburg Ky
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This truck I am refering to makes it's max hp between 1700-1800 RPMS. At 75 MPH it is running 1800 RPM's in 10'th gear. It is a 10 speed.
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Taco
VA
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well that is all good and well I was using generic class 8 truck specs. but the truth is it won't tow any better than a gas truck that has proper gearing for the task given equal horsepower.
it may use less fuel, no arguement there. and it may last longer at lower rpm but it is just as easy to make a turbo gas motor that will make as much torque at low rpm as a diesel and last just as long. diesel is for fuel economy, nothing else.
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64thunderbolt
Az
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All I can say is all you gasser owners come out west and try some of our mtns and you'll see how quickly the gassers die on the pulls we have. If you haven't been out here and pulled the grades we deal with you don't know what it's like. All the theories in the world don't mean anything. Come put your truck up beside a diesel on these mtn grades and find out.
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Hannibal
Tampa Bay Area
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No one is saying gassers rule. It's horsepower that determines how fast you tow up the grade. A NA gasser will lose horsepower at high altitudes where the turbo diesel maintains. I've said many times if we towed often or lived in the Rockies, I'd own another diesel for that reason.
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Sport45
Not far enough from Houston, TX
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Neither gasoline or diesel is a magic elixir that changes the rules of physics or thermodynamics. A 300hp @ 1800 rpm diesel running at 1800 rpm will pull the same as a 300hp @ 4500 rpm gas engine running at 4500 rpm. If both are appropriately geared to turn their respective rpm's at 65 mph they will both pull the same at 65 mph.
They won't sound the same or get the same mpg doing it, but both will gin along happily in their power band.
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64thunderbolt
Az
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Sport45 wrote:Neither gasoline or diesel is a magic elixir that changes the rules of physics or thermodynamics. A 300hp @ 1800 rpm diesel running at 1800 rpm will pull the same as a 300hp @ 4500 rpm gas engine running at 4500 rpm. If both are appropriately geared to turn their respective rpm's at 65 mph they will both pull the same at 65 mph.
They won't sound the same or get the same mpg doing it, but both will gin along happily in their power band.
What are you smokin??????????
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Jarlaxle
New England
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Nothing. He is absolutely 100% correct.
Please explain, in detail and with links to sources, EXACTLY how 300HP from a Ford V10 spinning 4500RPM is different from a 300HP C10 Cat at 1700RPM, 300HP from a Cummins ISB at 2400RPM, or 300HP from a turbocharged Honda at 8500RPM. If each engine is moving equal weight and geared appropriately, they will perform exactly the same climbing hills. It is basic physics!
Note: been there and done that at work. We had two tractors, both with 275HP...one got 275HP with about 850lb/ft from a big Cummins (I think an ISM), one got it with maybe 600lb/ft from a Cat C7. With the same weight, they climbed hills at THE EXACT SAME SPEED. The C7 just had to spin higher, and was geared accordingly. (Power peak was 2300 versus, IIRC, 1800.)
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