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Old 10-15-2020, 07:07 PM   #1
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Maximum Torque when towing uphill

My truck produces itís maximum torque at just under 4,000 RPM. Is that the engine speed (RPM) I should be running at while climbing?
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Old 10-15-2020, 08:15 PM   #2
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My truck produces itís maximum torque at just under 4,000 RPM. Is that the engine speed (RPM) I should be running at while climbing?
If you are over 75% of the GVTW On your truck then your truck will be more efficient and run cooler engine and tranny wise closer to 4,000 rpmís. If itís a short hill then no but longer climbs yes. Also using the tow haul button/feature if available when in traffic and needing to change speeds often is advisable. It prevents the tranny from shifting into overdrive and from shifting up and down from overdrive.
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Old 10-16-2020, 09:41 AM   #3
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It prevents the tranny from shifting into overdrive and from shifting up and down from overdrive.
Depends on the vehicle. Newer vehicles will still go into overdrive in tow/haul and it's perfectly acceptable but it will stay in each gear a little longer. That's why it's called tow/haul now and not OD off.
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Old 10-16-2020, 11:15 AM   #4
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Power is what moves you, not torque. Let the engine rev freely and do use tow/haul. The controller won't allow it to be operated at a damaging level (unless it's tuned by someone who doesn't know what they're doing).

Redline in a lower gear will almost always deliver more torque to the wheel than engine torque peak rpm in a higher gear. Even though the engine will be at a lower torque level, it is "delivered faster"; the gearing will enable higher torque at the wheel by leveraging the higher rpm from the engine.
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Old 10-16-2020, 01:13 PM   #5
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My max torque is at 2800 RPM I believe, so when I’m climbing hills I usually shift from 7 down to 6 to achieve that. I tow in tow haul mode and the only gear it won’t go into is 10, but I don’t go above 7th (Drive) anyway. Tow/haul works great for engine braking (sport mode brakes even better, but I won’t tow in that)
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Old 10-16-2020, 01:17 PM   #6
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JRM1493 is right.

It is power that counts when climbing hills, not torque. Your transmission shifts gears to get the desired torque to the tires and onto the road surface. Torque is a measure of force. Power is a measure of energy per unit time. To climb a hill, you need to add potential energy to your vehicle. To climb a hill more quickly, you need more power, rather than more torque. Go back to your high-school physics course to see the difference.

For some reason, many people are wrongly hyped up about torque, when it is really power that counts. Part of that comes from people selling low-revving diesels that have lots of torque, but only the same power as gas engine. The real reasons for buy a diesel are not to get torque but to get better fuel economy and the ability to run at full throttle for continuous periods of time (Cummins ISB 6.7 is my reference, but other diesels may be similar).

So, be happy if your engine is revving up to the speed where it develops maximum power rather than maximum torque. If you want to save the engine, keep it in a lower gear, higher revs and don't use full throttle. The higher engine speeds allow the engine to run cooler. Running at low, lugging engine speeds makes the engine run hotter.

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Old 10-16-2020, 02:16 PM   #7
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JRM1493 is right.

It is power that counts when climbing hills, not torque. Your transmission shifts gears to get the desired torque to the tires and onto the road surface. Torque is a measure of force. Power is a measure of energy per unit time. To climb a hill, you need to add potential energy to your vehicle. To climb a hill more quickly, you need more power, rather than more torque. Go back to your high-school physics course to see the difference.

For some reason, many people are wrongly hyped up about torque, when it is really power that counts. Part of that comes from people selling low-revving diesels that have lots of torque, but only the same power as gas engine. The real reasons for buy a diesel are not to get torque but to get better fuel economy and the ability to run at full throttle for continuous periods of time (Cummins ISB 6.7 is my reference, but other diesels may be similar).

So, be happy if your engine is revving up to the speed where it develops maximum power rather than maximum torque. If you want to save the engine, keep it in a lower gear, higher revs and don't use full throttle. The higher engine speeds allow the engine to run cooler. Running at low, lugging engine speeds makes the engine run hotter.

ĖGordon
I disagree. Torque is what gets the job done, not 'power' as you are referencing. If you are equating 'power' as horsepower, horsepower is a mathematical equation. Torque times rpm divided by 5252 gives you 'horsepower.'
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Old 10-16-2020, 03:04 PM   #8
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I recall my high school physics teacher emphasizing basic Newtonian mechanics and saying that energy was generated by exerting a force through a distance. As a result, lifting a 20,000 lb RV up 100 feet of (vertical) hill created a specific amount of potential energy, which is released or expended when the RV is allowed to roll back down the hill.

Power is a measure of energy that is created or expended per unit time. Kilowatts and horsepower are both units of power delivery Ė a kilowatt is slightly more than 1 horsepower. When you pay for energy in your home it is measured as kilowatt-hours, so you have to multiply the power (rate) by the amount of time the power was used in order to determine your energy consumption.

If you divide the energy measure (potential energy of climbing a hill or electricity in your home) by the amount of time for which it is used, you are back to kilowatts or horsepower. Thus, if you want your RV to climb a 100 foot hill in 15 seconds, you divide the potential energy by the time over which it is expended and you are asking for power to drive you up the hill. If you are willing to climb the hill in 30 seconds instead of 15, then you only need half as much power to do the job. In both cases, the force pushing the vehicle up the hill is identical, and the distance up the hill is the same, so the RV gets the same potential energy added by the time it gets to the top of the hill in either case.

Torque doesn't come into the picture except when it is converted to the force exerted by the wheels on the road to climb the hill. By that time, the engine torque has been multiplied up or down by the transmission and differential gearing, as well as the wheel radius. So, a (high-revving) 300 hp engine generating 300 lbs-feet of torque at the drive shaft will be able to climb the hill at the same rate as a (low-revving) 300 hp engine generating 600 lbs-feet of torque, once we bear in mind that the high-torque engine is attached to a transmission and rear end with higher ("taller") gearing in order to achieve the same road speeds as the high-revving rig.

ĖGordon
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Old 10-16-2020, 03:18 PM   #9
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HorsePOWER is a result of torque. Torque is a measure of force over distance (ft-lbs) now add in over a period of time (like gordonsick) explains and you have horsepower
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Old 10-16-2020, 04:19 PM   #10
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HorsePOWER is a result of torque. Torque is a measure of force over distance (ft-lbs) now add in over a period of time (like gordonsick) explains and you have horsepower
But horsepower is still a mathematical number.
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Old 10-16-2020, 06:10 PM   #11
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Two different ft-lb and lb-ft measures

One awkward and confusing issue in these discussions is that torque and energy are both measured in ft-lbs, but they are very different things.

I guess that is why careful writers are now measuring torque in lbs-ft, even though it is still a product of pounds force and feet of radius distance over which the torque is measured. That is, if I have a 1 ft long breaker bar and apply 50 lbs of force at the end, I get 50 x 1 = 50 lbs-ft of torque. That is the same torque as I get when I have a 2 ft breaker bar and apply 25 lbs of force at the end. Multiply the lever (radius) distance by the force to get 2 x 50 lbs-ft of torque. I think this is pretty common knowledge.

But we usually have to crack open a high-school physics text (or website) to see that energy can be measured in ft-lbs as well, but this measure is an entirely different beast from torque. Energy and work mean the same thing in Newtonian physics and mechanics. If we lift a 50 lb object over 2 feet, we have 50 x 2 = 100 ft-lbs of work, which is potential energy added to the object, which is now 2 feet higher. If we lift a 100 lb object over 1 foot, we have 100 x 1 = 100 ft-lbs of work. In both cases, we multiply the force times the distance to measure the work produced, which is the potential energy created by lifting the object.

Because of this confusion, it is less common to measure energy or work in ft-lbs. Instead, we go straight to Newtons, Joules and Watts to stay out of trouble:

A Newton is the metric measure of force https://en.wikipedia.org/wiki/Newton_(unit) which is approximately 0.22481 lbs of force.

A Joule is the energy or work done when a force of one Newton acts on an object over a distance of one Metre, which is 1 newton-metre. https://en.wikipedia.org/wiki/Joule

A Watt is a measure of the rate of flow of energy and it is equal to a flow rate of 1 Joule per second. A kilowatt is 1000 watts and that is about 1.34 horsepower. In Europe and Australia, automobile power is rated in kilowatts rather than horsepower.
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Old 10-16-2020, 06:14 PM   #12
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Horsepower vs. Torque

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Originally Posted by Springerdad View Post
But horsepower is still a mathematical number.
I confess I do not understand why there is a controversy on this issue. Both horsepower and torque are "mathematical numbers", but it is the amount of power delivered to the rear wheels of the tow vehicle that determines how quickly a load can be towed up hill.

The primary significance of the "maximum torque" rating is that it marks the point in the rpm range of the engine where it is operating at maximum efficiency. From that one might assume that operating at or near the rpm of max. torque might increase fuel mileage. Not necessarily.

Bottom line is that power is what determines how quickly a tow vehicle can accomplish its intended tasks.
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Old 10-16-2020, 06:23 PM   #13
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Aircraft engines: thrust or horsepower?

I know there are some pilots around this forum, and they may be quick to note that jet engine performance is measured in pounds of thrust, which is a measure of force. But, we really need to know what the jet speed is to convert thrust to horsepower. Encyclopedia Britannica explains it at https://www.britannica.com/technology/thrust-horsepower

If we consider the ubiquitous engine on a Boeing 747-200, NASA measured it as producing 55,145 lb of thrust at Mach 0.9 (871 ft/second). That turns out to be 87,325 hp (65,100 kW) Aerospaceweb.org | Ask Us - Convert Thrust to Horsepower

I've analyzed a gas-fired power plant that uses a modified 747 engine (GE LM 6000) and they produce about 45,000 kW in a single cycle mode (before recovering exhaust heat for combined cycle mode), so that's in the same ballpark.

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Old 10-16-2020, 07:11 PM   #14
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Maximum Torque when towing uphill

Back to the Op's question. My peak torque is 3,750 and peak HP at 5,000. I have had many hard pulls and around 4,500 has always done the job. You will figure out what is best for your truck as you go. My highest RPM ever was 4,800 for a short period of time. So in other words I routinely need to exceed my peak torque, but have never needed my peak HP. I am also towing at 98% of my GCWR so I need just about all the power it has in the demanding situations.
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Old 10-17-2020, 12:17 AM   #15
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Lots of misinformation. Torque is what gets you up a hill, horsepower is a timed measurement. If you think a gas engine that produces 375 horsepower and 450 ft lbs of torque will out pull a diesel that has 350 horsepower and 1000 ft lbs of torque you are very wrong. Why would those big rigs use them? The gas engine would be much cheaper but quite useless.
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Old 10-17-2020, 06:55 AM   #16
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I let the Tow/Haul button handle that issue!
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Old 10-17-2020, 07:17 AM   #17
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I can put 1000 ft lbs of torque to my rear wheels with my bare hands and a long lever. The problem is it will take a month to climb a hill because I can't even make 2 horsepower.

So the advantage of horsepower is then you can make plenty of torque through the gears, which are also just levers.

The advantage of that low rpm torque of a diesel is only fuel economy. It takes a certain amount of fuel per minute to make a certain amount of horsepower. If you can hold your speed with the torque at a lower rpm means you can hold your speed with less horsepower.

When climbing a hill just let the horsepower (a measure of work not force) do the work needed.
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Old 10-17-2020, 08:48 AM   #18
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My truck produces itís maximum torque at just under 4,000 RPM. Is that the engine speed (RPM) I should be running at while climbing?
Getting to techy in here. On long pulls keep your rpms around 4,,000 or just above with tow/haul mode engaged. Watch your temp gauge if it goes above 230 F turn on your heater to bring temps down. A trick that most havenít heard! Good camping to ya!
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Old 10-18-2020, 12:21 PM   #19
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That's why a diesel engine is far superior for towing. I have towed out west on I70 going over the Continental divide and back east on I40 going up and over Black Mountain. Towing a CEDAR CREEK 34RL with my 2008, Dodge truck equipped with the Cummins engine 350HP/650lb-ft Torque and the 68RFE auto, 3:73 gears. I have gone up and over these mountains in 5th gear and the engine rpm is around 2,000, doing between 60 and 65 mph.

What's nice about the Cummins Diesel 6.7L, engine is that the full engine Torque is produced around 1,400 RPM's . So I don't have to have the engine screaming to go up a mountain when towing my Creek.
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Old 10-18-2020, 08:23 PM   #20
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I don't know how you want to work it all out mathematically, but the simple real life experience for me is that pulling a 10K rv up the mountain into wv with my 2016 Ram 2500 6.4 Hemi simply could not go any faster as the truck was in second gear and near redline, would shift to 3rd and lose speed and downshift to second again . Same Hill, Same Camper, My 3500 Diesel Version of the same truck was a little over 1/2 throttle in 5th gear at 2000 Rpms and I certainly had reserve left to go faster had I wanted too, and traffic allowed it. Rear gearing 3.42 in diesel - 3.73 in Hemi.
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