Lugging a diesel engine?

[RoyJackson]

90% of the time my JD4300 is running between 1500-2000rpm and not under "load"...

Yep, run about the same here. That's where the hand throttle is set and I'll use the foot throttle for upping the RPM, when necessary.
Even with no load, I idle the engine at 1500 RPM...never below 1000.

I'm not enthusiastic about the "80%" rule" either, although the quote (quoted from another thread or forum) may have made a lot of sense in it's original context.

 

[milkman]

In trucking, we were told by Cat, Cummins, and Detroit that they were meant to pull down to 1000 RPM before downshifting, that's for the 4 stroke diesel, not the old 2 stroke Detroits. All the fleet trucks were driven that way and I'm not aware of any bottom end bearing problems. In 2,000,000 on the two that I owned, neither Detroit had an engine bolt touched. They max out at 2100 or 2200 RPM so that's more that 50% rpm drop. If they pulled down to 1100 RPM and were able to maintain that, then they run that till the end of the pull.

 

[RalphVa]

Lugging or the "lug" point depends on the engine size, hp & torque. We had a Fiat 124S sedan once. You didn't run its engine below about 2,000 rpm. It was only 1.4 liter. At the same time, I had a Triumph TR-3B. The engine on that car was from a tractor. It would do fine down to around 1,500 rpm (and quit revving at 4,500). On my VW Cabrio with 2.0 liter engine, the minimum rpm (stated in the owners manual and from operating experience) on it is 1,500. On our 2010 Jetta TDI, it will do fine down to around 1,300-1,400 rpm. It also has a 2.0 liter engine.

My 4010's lug point seems to be around 1,500 rpm in most cases. Going up hill and with a bit of load, the minimum for it to not strain or run unevenly is around 1,800 rpm. Running the bush hog in heavy grass? You better be at PTO speed, about 2,600.

Lugging is the point at which the engine appears to strain or possibly run unevenly. In the case of the Fiat, you didn't lug it because the oil pump just plain wouldn't put out enough oil flow/pressure to keep the bearings from not being fully lubed.

My grandfather once had a Plymouth V8 with 3 speed stick shift. He frequently drove it like the proverbial Indian or Singapore taxicab driver. 1,2,3 and maybe 10-15 mph he's in high gear. Dad took over the car and almost immediately had to replace main bearings on the engine. Grandpa's lugging had ruined the bearings due to too low oil flow.

Ralph

 

[SPYDERLK]

Lugging or the "lug" point depends on the engine

My 4010's lug point seems to be around 1,500 rpm in most cases. Going up hill and with a bit of load, the minimum for it to not strain or run unevenly is around 1,800 rpm. Running the bush hog in heavy grass? You better be at PTO speed, about 2,600.
Ralph

That is unusually high for a low reving engine. I would question the condition of an engine that acted thusly.
larry

 

[Eagleview]

Diesel engines in most applications use the engines torque produced down low and not so much the horsepower produced higher in the rev range . My New Holland TL100A produces maximum torque at 1400 revs and that's where I keep it when working hard . I use the 1000 rpm PTO position and dial the engine back too 1400 which gives me around 540 at the PTO . I would suggest you look at your tractor specs and see where it's maximum torque is made and run it there . Obviously if you only have a single speed PTO you have no choice in the matter .

 

[MicroPilot]

Isn't the idea of running the engine RPM above the torque band when using the PTO, so that when the engine gets a load it falls back into the max. torque band and has a chance to "power through" the load? If you run in the max. torque RPM band, if the engine gets loaded it has no "reserver" to fall back on.

 

[Eagleview]

You are correct when talking about a tractor doing extremely hard work .

For the type of work I do and that of hobby farmers etc , I see no need to run an engine at wide open throttle . If you look at this Dyno chart , it shows an engine's horsepower and torque curves . As you can see this particular engine can be run at 1700 rpm before the horsepower starts to drop off which is only about 10hp down from full throttle , but looking at the torque curve the engine will lug all the way back too 1200 rpm and is still making 800 ft/lb of torque which will carry it through a tough patch of grass etc. Torque = twisting force on a shaft and is what does the work , Horsepower figures in my opinion just sell tractors .

 

[irvingj]

I might be way off base here, but the OP's quote... that was referring to over-the-road trucks, yes? Aren't they just about all turbo-charged? Other than the oil issue, could that be the difference?

I know on my Jetta TDI, it's recommended the you "drive it like you stole it" --that is, much higher shift points/higher rpms than what I've been accustomed to-- to keep the turbo from carboning up.

For someone who prefers high-torque/low-rev engines, that took a bit of getting used to!

 

[sixdogs]

I might be way off base here, but the OP's quote... that was referring to over-the-road trucks, yes? Aren't they just about all turbo-charged? Other than the oil issue, could that be the difference?

The reference was to CUT and utility sized ag tractors. While I never purposely "lug" an engine as described here, I often just use the foot throttle since the work is light and there is no chance of lugging in the obvious sense. But should I be doing this?
Should I instead set the hand throttle at a higher RPM even though I have no need for the power created? Are there degrees of unintentional lugging even though it does not appear that I am "lugging" in the textbook sence?

 

[PHILIP8N]

You are correct when talking about a tractor doing extremely hard work .

For the type of work I do and that of hobby farmers etc , I see no need to run an engine at wide open throttle . If you look at this Dyno chart , it shows an engine's horsepower and torque curves . As you can see this particular engine can be run at 1700 rpm before the horsepower starts to drop off which is only about 10hp down from full throttle , but looking at the torque curve the engine will lug all the way back too 1200 rpm and is still making 800 ft/lb of torque which will carry it through a tough patch of grass etc. Torque = twisting force on a shaft and is what does the work , Horsepower figures in my opinion just sell tractors .

Better check that torue curve, something is way off, numbers dont add up. What engine is that for? Philip.