Towing effort?? - Page 2 - Montana Owners Club

rubble express · 08-04-2008, 05:54 AM

I think all vehicles benefit from opening them up and letting them stretch there legs and get a few good lungs full of air once a month (drive it like you stole it). However, I wouldn't reccommend it with a 13+k trailer behind it. As far as speed goes, our truck seems to be happiest around 2000 rpm which translates to about 63-64 mph. I feel totally in control at that speed and I think it's a reasonable speed as far as other drivers are concerned. Like Rich said, most big rigs have slowed down alot. With the amount we are able to travel while we are still working, the mpg's are not really an issue. 10 vs 10.5...who cares, it's all bad. JMO.

Delaine and Lindy · 08-04-2008, 06:27 AM

I in the past towed at 65 mph or the posted speed if it was less. I now tow at 60 and the Durmax/Allison 6 speed turns in the area of 1500 to 1600 rpms and doesn't lug the engine. And fuel mileage was between 10 and 12.5 mpg towing 22,160. Not sure what we will get with the new 2009 (SOB) its heavier unit. Most heavy units aren't designed to be towed above 65 mph, yes I have towed at 68 mph for 1,675 miles and stopped two to get a little sleep. Was it safe, probable not but I was running Goodyear G614's, if it had been some other brand, I'm not sure if I would have run that speed. Again below 65 mph is recomended for most trailer tires. GBY....

Bruce Lenhardt · 08-04-2008, 07:36 AM

Richfaa Wrote:
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Here is what I found with the 08, 6.4L Ford.. 63/65 seemed to be "The sweet spot" However on our last long trip we slowed to 60MPH and the MPG increased at least .5 to .8 mpg.
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My experience with the 08 6.4 is about the same as Rich'es. Mine just seems to pull better at 63/65 mph.

H. John Kohl · 08-04-2008, 08:28 AM

Quote:

quote:Originally posted by Wiarton William

The point is......is it hard on my truck to let it(or make it) LUG and work hard in order to take e down the road....if it works hard at the lower speeds does my mileage sufffer... due to the harder tow?????

My wife an I have discussed this because I have the manual and can really let it "lug", pull at 1000 rpm. The Torque on the diesel is at the low RPM while on a gas engine it is at the high RPM. I find my sweet spot is between 1500 and 1700 and that is about 55 to 60 MPH for me. My turbo kicks in at 1400 to 1500. Because of my style turbo I do not get full boost until about 2200 RPM.
With all engines more RPS is more fuel but especially noticeable with diesel.

bigred715 · 08-04-2008, 01:50 PM

ve and always will drive 60 when towing the trailer. Just finished a 2 week trip from Eugene Oregon up t Leavenworth Washington and traffic is definately driving slower and my truck seems to run best at a minumum of 60. I watch behind me and always use the right lane or passing lane when I can.

KathyandDave · 08-05-2008, 03:09 PM

At the risk of sounding like my high school science teacher...on the flat, at a given speed, the power of the engine and the fuel it consumes are punching through the resistance of rolling friction and of the air. The rolling friction consists of the tires on the road and all of the mechanisms in the vehicles, including air conditioning. It shouldn't change noticably if you speed up from 60 to 66 mph, a 10% increase (somebody check me on this?). However, the air drag increases with the square of the speed, which makes a huge difference. The increase from 60 to 66mph increases the drag by 21%. The engine has to exert way more power than 10% to offset a speed change of 10%.

Waynem · 08-05-2008, 03:47 PM

Kathy - good post!

H. John Kohl · 08-05-2008, 04:13 PM

Quote:

quote:Originally posted by KathyandDave

At the risk of sounding like my high school science teacher...on the flat, at a given speed, the power of the engine and the fuel it consumes are punching through the resistance of rolling friction and of the air. The rolling friction consists of the tires on the road and all of the mechanisms in the vehicles, including air conditioning. It shouldn't change noticably if you speed up from 60 to 66 mph, a 10% increase (somebody check me on this?). However, the air drag increases with the square of the speed, which makes a huge difference. The increase from 60 to 66mph increases the drag by 21%. The engine has to exert way more power than 10% to offset a speed change of 10%.

You are correct. Cummings did a study on big trucks and found 55 MPH was the transition point from rolling resistance to air resistance. They claim big trucks will loose 1/10 MPG for every MPH over 55. So running 65 drops one mile per gallon.
I can find my link to this study if needed.

Wiarton William · 08-06-2008, 01:04 AM

OK, you guys got me now......my High school science teacher aid many times....Chadbolt IF You Dont pay attention you are going to end up selling used cars or busting rocks for the next 40 years.....I dont want to slow traffic down, hate being a slow poke and dont want to inflict a "hard drive" on the truck and create unnecessary repairs... I will have to let it find the "sweet spot" and go from there...

mgdg · 08-06-2008, 02:29 AM

I find that pulling at 63mph(100kph)and running at 16-1700rpm is the "sweet spot" on the Cummins. I set the cruise and go, if I encounter a steep grade off comes the cruise. Why be in a hurry, at least you`ll get there safe and its a lot easier to stop these monsters, then at those higher speeds.

KathyandDave · 08-06-2008, 06:43 AM

The fuel consumption goes up faster than the additional speed it buys. Every additional mph costs more fuel than the last one. In the rest of our lives, we're used to paying LESS per unit, the more units we buy, or at least pay the same, but not MORE.

Is the "sweet spot" the point of maximum torque? Here's a link to a graph showing the published torque curves for the Duramax, Powerstroke and Cummins. The writer is a bit skeptical of the accuracy, but the left "corners" for the Duramax and Cummins look very similar to the "sweet spots" people report.

Please use the "short form" to post long links. Your long link causes a horizontal scroll. You can find out how to make a "short link" on the MOC Forum under the Geek Squad area.

Thank you. RVWheels

http://www.turbodieselregister.com/
forums/6-7l-engine-transmissions-
2007-5/180954-cummins-vs-powerstroke
-vs-duramax-hp-torque-curves.html
Torque graph link - RBS

Maybe the mileage is best in the "sweet spot", where the engine is most efficient?

hookman · 08-06-2008, 02:12 PM

We just completed a trip to Central Washington. Once the truck was broken in I traveled at 60 mph which I always try to travel at while pulling not for mileage but it is a speed which I feel comfortable at for control. A lot of trucks passed me on the flat areas but I passed them on the hills still doing 60 mph. Around this speed the truck seems to pull fine at around 1700 rpm. I am not checking mileage yet as the truck has not enough mileage on it only 5000kms.

c214dick · 08-07-2008, 05:52 AM

We feel comfortable towing at 60 mph. The cruise doesn't down shift unless we hit a grade which I try to anticipate and take it out of cruise. 60 mph also seems to be our magic number assuming our speedometer is correct which means were probably at about 58 mph. I never seem to have a problem with traffic backing up because it's their problem, not mine. I would truely be a "happy camper" if the Feds went back to the mandatory 55 mph.

bsmeaton · 08-07-2008, 08:41 AM

Quote:

quote:Originally posted by c214dick

I never seem to have a problem with traffic backing up because it's their problem, not mine. I would truely be a "happy camper" if the Feds went back to the mandatory 55 mph.

Ah - road rage in the making. Gee-zoots

c214dick · 08-07-2008, 10:02 AM

No road rage here. The older I get the slower I go. That way I can see all there is to see.

HamRad · 08-07-2008, 11:03 AM

Dick,

I think the reference to "road rage" was that you might be causing some by your going slow. I'm sure you would never succumb to road rage.

As long as you are going the speed limit then you are under no obligation to worry about folks piling up behind you. However, in California, if you are going slower than the speed limit and more than 5 vehicles stack up behind you you are then obliged to move over and let them pass. Failure to do so could, indeed, cause some road rage.

HamRad

c214dick · 08-07-2008, 05:18 PM

I have not noticed any "back ups" due to me doing 55 - 60 mph. If I'm on the expressway I'm usually in the right lane so traffic can pass me. I may be guilty of road rage though because of the folks that don't know how to merge when entering the expressway. I do adjust my speed when necessary to avoid problems. On secondary roads, two lanes, the speed limit is usually no more than 55 so I'm OK there.

As for California I don't see us making too many trips out there with Monty as long as diesel prices are so expensive.

HamRad · 08-07-2008, 07:46 PM

Dick,

I'm with you on the folks not knowing how to merge! You would not think that would be all that difficult a process! But I've come down with the early stages of Road Rage dealing with some of them. Or just as bad the guy who comes flying around you only to cut directly in front of you barley making it to the road he wanted to exit on!! If he'd stayed behind you he would not now have to pull off somewhere soon to change his pants!

On our secondary roads as well as our freeways..... vehicles towing must not exceed 55mph. That includes the eighteen wheelers as well as those of us towing Monty around. 55 is the max limit we are allowed to drive! Period!

Sorry you can't make it out to CA. In spite of our drawbacks we do have some of the best scenery in the world. Certainly well worth a trip someday.

Hope to see a lot of you out this way as diesel continues to drop like a rock. Why we're all the way down to $4.75 here in good old Bakersfield!

Drive safely! And see you on down the road.

HamRad

c214dick · 08-08-2008, 03:12 AM

Thanks for the invite. Diesel is 4.39 - 4.79 from my neck of the woods north about 25 miles towards Milwaukee. I kept reminding Louise that if she wanted to travel with Monty that we needed to budget .50/mile just for driving. Now that diesel has dropped a little I can adjust that to .45/mile but still not cheap enough to get us to California. I think the closest we might get is to Colorado where one of our sons and his family live.

sreigle · 08-09-2008, 02:32 PM

I blame a lot of the poor driving we see today on the lack of required driver education in schools today.

Kathy, good post on the science teacher comments. Another factor that has to be considered, though, is terrain. If I'm towing on the flat I can tow at 58 mph and get better towing mileage than I would at 63 mph. However, once I get into hilly terrain with more than just little hills, my Dodge towing that much weight will downshift going up many of the hills. If I speed up to 63, the downshifting ceases on all but the steepest of hills and my mileage is actually as good or better than it was at 58 mph in that hilly terrain. The hypothesis put forward by the teacher likely includes an assumption of "all other factors being equal." In this case the engine rpm differs in the different terrain. Not to mention the frequent shifting can heat up a transmission in a hurry.

That's what I'm seeing, anyhow.

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