At what point are you lugging a diesel?

[another Todd]

In towing my 10,000 lb 5th wheel travel trailer with my 2015 Ford Powerstroke Diesel and 331:1 gears I can run on the highway in 6th gear at around 60mph and 1400 rpm, low boost and hitting any hill causes a downshift but seems to pull fine on the flat. When doing this the engine is somewhat noisy, and sounds like it is pinging. Upon acceleration the turbo cannot build pressure so it downshifts. 5th gear is around 1800rpm and there it accelerates without hesitation and generally does not down shift when hitting moderate hills and the engine is quiet.

Is 1400rpm in the above scenario lugging? Could damage occur? Would it be better to stay in 5th gear while towing? I generally let the automatic do the shifting but I do keep it in the tow haul mode.

 

[Olas]

Not for pedantry, but, is that 331:1 or 3.31:1?

Also, if it sounds like its pinging and kicks down when you want to accelerate its probably on the verge of lugging by design for mpg. Engines are generally happier a bit higher up the torque curve with mild throttle opening, compared to just off idle with 2/3 throttle.

 

[Ramblejam]

 

[Olas]

By that graph, and not knowing the vehicle/trailer total weight I'd say 1550-1600 rpm as a min. before lugging ( in an appropriate gear)

 

[bullwinkle]

In tow/haul, the transmission controller (PCM) is going to change the shift curves & quality, holding gears longer & shifting harder. To lug a diesel, the engine is going to have to get below 1100-1200 RPM-they have enough low end torque (unless you have a 6.0) to move a lot of weight, & it'll downshift by itself if you don't have enough. I would stress more over transmission temperature, myself. For instance, the old IDI 7.3 in my sig actually reaches its torque peak by 1200 RPM.

 

[another Todd]

Yes on the 3.31:1.

RE: Graph...1550 or 1600 is about the rpm needed to obtain full turbo boost, so that chart looks dead on. At 1400 rpm I cannot obtain full boost and it drops off on hills until it shifts.

I've never seen transmission temps above 210F
Highest oil temp I've seen is 245F while pulling/cresting a hill.

 

[mjoekingz28]

It seems many engines have gone to using some rpms over the years. I used to want a SBC and lug it around town at 1000rpms. Now, I have a LS derived motor that likes to spin just a lil before making things happen.

I also consider torque to be different at different parts of the band. It seems, to me at least, that 1000lb-ft at 1000rpms will be different than 1000lb-ft at 4000rpm.




I cannot speak for engine internals, but I think lugging isnt to good for the engine mounts, transmission, driveshaft, rear end differential..........




It sure is sweet to see how low you can spin a motor safely!

 

[heynow]

In my opinion, it is not possible to lug a diesel engine attached to an automatic transmission, as it will downshift before this happens.

My rule for lugging has always been that if the "throttle" is floored and the engine speed does not increase, you are lugging.

 

[demarpaint]

You should be fine using tow haul mode. I would avoid using 6th gear.

 

[SwampSurvivor]

Originally Posted By: mjoekingz28
It seems many engines have gone to using some rpms over the years. I used to want a SBC and lug it around town at 1000rpms. Now, I have a LS derived motor that likes to spin just a lil before making things happen.

I also consider torque to be different at different parts of the band. It seems, to me at least, that 1000lb-ft at 1000rpms will be different than 1000lb-ft at 4000rpm.




I cannot speak for engine internals, but I think lugging isnt to good for the engine mounts, transmission, driveshaft, rear end differential..........




It sure is sweet to see how low you can spin a motor safely!


Even "older" engines people seem to think need to lug around. A lot of people are perfectly content with their Jeep 4.0 on 3.07 gears and 31'' - 33'' tires. They don't realize if they gear it to 4.10 or 4.56 and get it so it's cruising at 2000-2500, it will get significantly better mileage.

With that said, there are engines that work better at low RPM. Jeep 4.0Ls won't "lug" and damage themselves until you are well, well below 1000 RPM.

My Focus has a thing in the owners manaul that says to not operate it under load under 1250RPM.

 

[roadrunner1]

The PCM/ECM is much smarter than anyone behind the wheel can be. Your truck is programmed to downshift/upshift to properly maintain desired speed, without causing any damage.
With my experience with my own 6.7(3.31 rear end) just sit back and enjoy the ride.

 

[Charlie1935]

Cummins said that 35 years ago.

 

[Chris142]

Originally Posted By: heynow


My rule for lugging has always been that if the "throttle" is floored and the engine speed does not increase, you are lugging.
YEP! The owners manual for my old Peterbilt said to run 1700-2100 rpm ,no less no more when pulling a load or it may "Suck a liner". Said 1900-2100 when pulling a hill

 

[clinebarger]

I do not tow in 6th gear in my truck, And I have 3.73:1 gears, Couldn't imagine doing it with 3.31:1 gears. Get on top of your torque curve (About 1800 according to the graph), My Duramax curve is very similar with less max torque & likes 1800-2100 cruising down the highway towing heavy.

 

[roadrunner1]

I have absolutely no problem towing heavy with my 3.31 rear end, just let the truck do the thinking, at 70 mph the engine is approx 1,550 rpm. Where I'm located its relatively flat and I don't tow in the mountains.

The Ford 6.7 doesn't need to be downshifted to maintain peak performance, it will do it for you as its not 1990 any longer.

 

[MinamiKotaro]

You're lugging it when it starts to jerk violently. That's always been my metric.

 

[Srt20]

Originally Posted By: heynow
In my opinion, it is not possible to lug a diesel engine attached to an automatic transmission, as it will downshift before this happens.

My rule for lugging has always been that if the "throttle" is floored and the engine speed does not increase, you are lugging.


This whole post is truth.

 

[jhellwig]

Put it in drive and set the Cruze. Let the engine management do its thing. Diesels get noisy when they are working hard. You don't hear a ping. You will hear a boom before a ping.

 

[mjoekingz28]

How come you can hear the diesel 'knock' or clatter at idle, but as soon as you rev it or start moving- it goes away?





This is not to be confused by the muffling of the higher frequencies when something passes between your ears and the engine as it idles.

 

[dareo]

On most diesels Peak Torque is also Peak Efficiency so i would want the RPMs to be at least 1600 under load based on that chart. 1400 is not far off and it may be ok on flat ground with no head wind.