Quick general towing question...

[Randy in Maine]

When towing up a long hill, doesn't it make sense to just try to stay on top of the engines torque curve?

Example, my engine develops maximum torque ~300 foot pounds at about 3400 RPMs, so when I am pulling uphill I try to just stay pretty close to that 3400 number or a bit less since the engine really doesn't make any more power at more RPMs. Therefore, if I can't hold that 3400 due to the load, the elevation, & steepness of the hill, I normally just drop it down a gear for a while if I need to.

I was trying to explain it to someone yesterday and they sort of looked at me like I was clueless.

[Bill and Earline]

That's exactly right. I used to have to do that when towing with my 2003 4Runner V6. Not so much with the EcoDiesel. Cruise control does fine except in the most extreme circumstances, since the diesel torque is good at most rpms.

The sound of a "working" engine at higher rpms bothers those who don't know about torque curves and peak torque stats, so turn up the radio in those situations, or explain that you're giving the engine a good work-out, or "cleaning out the pipes". Those explanations work for awhile.

[marsman]

Randy, that's the way I've always understood it, keep the revs up and stay in the torque curve. Even my mechanics at the Harley shop tell me that the most common mistake riders make is to "lug" the engine at low rpms, hard on the engine and tranny. Engines do much better when they're breathing freely.

[Brian B-P]

Originally Posted by Randy in Maine

When towing up a long hill, doesn't it make sense to just try to stay on top of the engines torque curve?

Not necessarily. The efficiency of the engine under heavy load is usually best around the speed for peak torque, but that's not the best speed for every condition.

Originally Posted by Randy in Maine

Example, my engine develops maximum torque ~300 foot pounds at about 3400 RPMs, so when I am pulling uphill I try to just stay pretty close to that 3400 number or a bit less since the engine really doesn't make any more power at more RPMs.

Power is torque multiplied by speed. Although there is less torque available at higher engine speed, it can make more power up there.

300 foot pounds at 3400 RPM is 194 horsepower (145 kW); the engine would produce more at higher speed. Obviously this isn't a 1979 Westfalia... what's the tow vehicle?

The gears in the transmission multiply the engine's torque and divide the speed by the same ratio. When you shift down, you are selecting a lower gear, so the engine runs faster and even if it produces a little less torque, after it has been multiplied by the ratio of the lower gear of the transmission the torque out of the transmission is higher.

For instance, if from 3400 RPM the next gear down gave you 4800 RPM and the engine was down to 250 lb-ft, that would be 228 horsepower (higher, despite the lower torque) and the torque out of the transmission would be 18% higher than in the higher gear. Of course real values would require specific engine and transmission specifications.

In the other direction, if not much power is needed, so the engine is only lightly loaded at (for instance) 3400 RPM, then it's not at peak efficiency. A lower engine speed and higher load (torque) combination (providing the same power) would likely yield higher efficiency and less engine wear.

[Mountain Mike]

You're correct by staying on the up side of the torque curve. Down shift and run up the hill with the engine at it's ideal torque output RPM. It's a bit louder but, way easier on the engine and cooling system. When climbing a long hill in a higher gear the a larger portion of the fuel creats excess heat in the engine, not propelling the rig along. When pulling a long hill I down shift and run up at 1/2 throttle at about 3400 RPM. Good Luck.

[UncleTim]

I see this debate play out every time I go West fro Georgetown, CO up to the Eisenhower Tunnel that goes under the continental divide at 11,000 feet.

Keeping the rpm's high does help, but the grade varies and what can be done right outside of town is harder up the road when the grade and elevation increase.

You can also stick the truck in 'Tow Haul' mode if you have one. That will do the same thing, more or less.

The problems start when one car/truck enters the left hand, faster lane and then bogs down. Everyone in the lane loses their rpm's and the fast lane becomes gummed up with slow cars. Once most of those cars lose their rpm's, it is difficult or impossible for them to regain their former speed. The grade will not allow it.

My answer was to get a 5.7L, V8 and put that problem to rest. I see it every time up the tunnel approach, and like lots of other thing, it seems to be getting worse.

[JeffreyG]

Originally Posted by Randy in Maine

Example, my engine develops maximum torque ~300 foot pounds at about 3400 RPMs, so when I am pulling uphill I try to just stay pretty close to that 3400 number or a bit less since the engine really doesn't make any more power at more RPMs.

The amount of power the engine is making dictates the speed up the hill, so if you want to go up the hill faster, run the engine at the peak power point.


As Brian B-P says, power = torque x rpm. So the peak torque point is probably not where the engine makes peak power.


Most modern semi trucks make peak torque at 1100 rpm and are geared to run there at highway speed. But when they are grinding up a 6% grade at 27 mph with the hazards on, they are running 1600 rpm and making peak power. Nothing to do with peak torque.

[Randy in Maine]

Thanks for the well thought out responses.

For the record the tow vehicle is a 2002 Toyota Tundra 4WD access cab with the 4.7L DOHC V8. Cast iron block 94mm bore and a 84mm stroke. Quite dependable and well maintained, but a bit of a heavy drinker at 16 mpg and about 12 mpg pulling. It puts out about 315 foot pounds of torque at 3400 and 245 HP at 4800. 3.91 gears and 4speed auto with the OD lockout, but no "tow mode", so I can't easily modify the air:fuel mix. It is rated to pull about 7100 pounds and has a load capacity of about 1700 pounds. I am thinking that it should be adequate for the 21C Escape that I have on order. If it breaks I can either 1) fix it or 2) just buy a newer one with the 5.7L engine.

[JeffreyG]

Originally Posted by Randy in Maine

It puts out about 315 foot pounds of torque at 3400 and 245 HP at 4800.

So the fastest this thing will go up a hill at 4800 rpm. My guess is that if you hold your foot to the floor on a long grade, that about where it will go.

If you are on a lesser grade or happy slower, then running lower rpm at less than peak power will be quieter and a bit more comfortable.

Some of this is moot with an automatic transmission. It's going to do what it's going to do based on pedal demand and speed.

but no "tow mode", so I can't easily modify the air:fuel mix.

AFR is going to run stoichiometric no matter what you do, it's an SI gas engine.

Tow haul modes typically just adjust transmission shift points. On some modern vehicles they also adjust the smart voltage regulator to output more amps.

[Randy in Maine]

I am trying to figure out just why I would want to actually go fast going uphill on a long steep grade.

I am actually one of those guys who like to look at the local geology and even road cuts. Plus I am retired and will be on vacation.

[JeffreyG]

Originally Posted by Randy in Maine

I am trying to figure out just why I would want to actually go fast going uphill on a long steep grade.

Depends how slow you are going. People are a little spoiled by the kind of power you can get in a modern passenger vehicle.


Guy who used to be on my team had a funny story about his ~1990 Ford Econoline and his 32' TT. He's laboring up a long grade at over 9000 feet elevation. The van is down into second gear and moving under 30 miles per hour.


His wife says "What wrong with the van!?"


He says "It's called......a mountain!"

[DanandDaphne]

We have the same truck same year and a 2018 5.0 TA ours does fine, a little slower on the mountain passes than some but not bad.

Also as far as gas millage, yes it doesn't get great mileage but we own it and it's reliable. Whereas a new truck we would have to buy for $40K+ so we figure we can buy a lot of gas before the extra mpg would add up to $40K.

[Randy in Maine]

Originally Posted by DanandDaphne

We have the same truck same year and a 2018 5.0 TA ours does fine, a little slower on the mountain passes than some but not bad.

Also as far as gas millage, yes it doesn't get great mileage but we own it and it's reliable. Whereas a new truck we would have to buy for $40K+ so we figure we can buy a lot of gas before the extra mpg would add up to $40K.

I can relate to those very valid points. For the record, I have driven VW buses for many years and I know all about driving slow.

[Brian B-P]

Originally Posted by Randy in Maine

For the record the tow vehicle is a 2002 Toyota Tundra 4WD access cab with the 4.7L DOHC V8.
...
It puts out about 315 foot pounds of torque at 3400 and 245 HP at 4800. 3.91 gears and 4speed auto...

Thanks for the details, which confirm that when you need more power than you can get at 3400 RPM, you can get it if you can run the engine faster.
315 lb-ft @ 3400 RPM -> 204 HP (e.g. 2nd gear @ 50 MPH with P265/70R16 tires)
268 lb-ft @ 4800 RPM -> 245 HP

The challenge is that with only four transmission ratios, shifting makes too big a difference in engine speed. 50 MPH in 2nd gear corresponds to 3400 RPM (as long as the torque converter clutch is locked up) if I've done my calculations correctly; shifting just one gear down is all the way to first... and an unreasonable 6230 RPM. Shifting up just one gear for better fuel economy means to 3rd gear and 2220 RPM, which might work but can produce perhaps 100 horsepower, which might not be enough.

JefferyG covered the rest of what I would say, very well.

[Iowa Dave]

Originally Posted by Randy in Maine

I am trying to figure out just why I would want to actually go fast going uphill on a long steep grade.

I am actually one of those guys who like to look at the local geology and even road cuts. Plus I am retired and will be on vacation.

Hi Randy
Tensleep canyon in Wyoming is for you. The rock strata Is labeled as to the Era. Put it on your list if it’s not already there. Up or down, not challenging and pretty.
Iowa Dave

[Randy in Maine]

Thanks (fellow Hawkeye) Dave! I will note that on my future travels!

[HABBERDABBER]

I drove thru and out of Ten Sleep, WY, in a 1970's Volvo wagon, a standard 4 banger with Stromberg dual carbs. As elevation & slope increased, power decreased, greatly, along with an increasing vapor trail of grey camouflage smoke coming out of the exhaust. I didn't know if I'd make it. Looking over the cliff , I saw what I thought was a burning vehicle at the bottom, on the way up. Something was burning, way down there.



Maybe it was my previous experience before leaving Ten Sleep that spooked me. I stopped at the only business open on this 4th of July day, the only bar in town, and open. I needed not a drink, but to use their phone to connect up with a buddy who was also on this trip but a day or 2 behind. A couple of cowboys were passed out, at 10 AM, outside and perched, slumped along the wall of the old, white, wooden bar building. Walking into the bar was similar, with a few folks tanking up. The bartender was accommodating to allow me to use a phone card to use their phone. This is late 1980's...pre-cell (PC?)



Ahh.......Ten Sleep. I missed the geology lesson that time, but I got other lessons.


But I digress.............

[Iowa Dave]

We drove the canyon both up and down several times pulling our large fold down with the Ford Bronco, 1982 Buick LeSabre and 1987 Grand Marquis. Never had a problem with any of them. Haven’t been that way for a few years. After making the comment today I got to thinking about it and sent away for a bunch of Wyoming Tourism info. Not sure when, but in the next year or two. As Rita said, we’ve seen Yellowstone, the Tetons etc. several times so a non-destination trip might be good. Have had some good times in Wyoming. Not to be missed: King Ropes in Sheridan. Better than most museums, free and a great place to buy a new pair of elk skin roping gloves and a King Ropes hat. Big Wonderful WYOMING.
Iowa Dave

[Ret.LEO]

Originally Posted by Randy in Maine

Thanks for the well thought out responses.

For the record the tow vehicle is a 2002 Toyota Tundra 4WD access cab with the 4.7L DOHC V8. Cast iron block 94mm bore and a 84mm stroke. Quite dependable and well maintained, but a bit of a heavy drinker at 16 mpg and about 12 mpg pulling. It puts out about 315 foot pounds of torque at 3400 and 245 HP at 4800. 3.91 gears and 4speed auto with the OD lockout, but no "tow mode", so I can't easily modify the air:fuel mix. It is rated to pull about 7100 pounds and has a load capacity of about 1700 pounds. I am thinking that it should be adequate for the 21C Escape that I have on order. If it breaks I can either 1) fix it or 2) just buy a newer one with the 5.7L engine.

Are you sure about your CCC? Seems high, check the door to be safe. I have a 2006 TRD SR5 with tow package, tow/haul, 4.30 rear and my CCC is 1330LBS. I don't think you have a thing to worry about for towing. Tundra's are underrated for towing.

[cpaharley2008]

My Ram 1500 is closer to 1200# CC. I also found out it had a mini spare that was not usable while towing, so check your spare to see if it is full sized and check it's capacity......I had to buy a full sized wheel and tire to carry in the truck bed.