Asher

I hear alot of guys say that you have to stay in the 1700+rpm range to keep from lugging the engine to much.

I don't agree or disagree, but I have to know at what point do you actually consider "lugging" the engine? I ask this because I look at the specs on the new engine and the max torque is @ 1600 rpm's. If the max torque is at this low of an RPM then there must be a decent amount of RPM range below this that is still usable without "lugging"... I have a hard time believing that you only have about 1500 rpms of usable power if you follow this 1700 theroy.

I usually drive by my EGT and would only shift out of O/D if the truck is hunting, or the EGT gauge dictates more rpm's but that has only happened maybe once. My truck pulls hills at 1400 rpms like no ones business, but I am told that this is a no-no... I can't understand why chrysler would allow the auto tranny to pull the engine down that low if thier could be potential damage. Again I don't agree or disagree but I would like a little better answer then "just because; or my uncles, buddies, grandpa stories".

So is there anything written in stone (maybe from cummins source) that says at what rpm this engine is actually considered lugging (or damaging)?

I ask this for two reasons, towing in O/D quickly makes the truck a fuel pig unless you run 55mph (to keep it around 2k) and also to try and find out what is truth and what is fiction / hear-say...

So fire away guys, lets hear some comments and any evidence that backs them up. Let me make it clear for the third time: I don't agree or disagree, I just want to know.

Thanks

Herrin811

https://www.dieseltruckresource.com/...hlight=lugging


Posts 4 and 6

https://www.dieseltruckresource.com/...lugging+torque

Post 2 and post 6

Post 6 from Cummins


Been looking myself

blackdiesel

they say dont lug a 5 speed 2nd gen. Because if ya do, it will jar the 5th gear nut loose.

Asher

Thanks guys, I see alot of comments (from the link) but I don't see much more than a bunch of opinions. I guess I would like to know at what point rpm the ISB stops creating smooth balanced revolution, which to me would be the point of lugging.

Thanks for the tranny info, I am not up on the manual problems, but that would make sense if the crank shaft is causing viberation, or could it be that the pressure on the O/D gears causes them to flex enough to cause thier own viberations.

Maybe I am not thinking right, but I still have a hard time believing that if the max tq rating is at 1600 that this engine isn't good to (say) maybe 1300 rpms or so. I don't really know.

Herrin811

Under full load is the key phrase in the first statement...Running around town is hardly full load...Going uphill empty isnt really a load...Trying to maintain speed while pulling 20K uphill in OD, and dropping from 1800 to 1200 rpm without downshfting would be lugging...Gravity at work against the engine

phox_mulder

Watch your EGT guage, it will shoot up pretty fast if you are lugging it.


phox

nickleinonen

with an automatic transmission, you can't lug the engine unless you have full manual control over the VB and torque converter lockup. if the transmission is stock/somewhat stock, you won't ever lug it... leave it in drive and forget about it.

rock

Phox and Nick hit the nail square on the head. For us folks that row gears, we need to watch the EGT. As an example, I have a hill by my house I go up every day, rowing through the gears empty I can shift into 6th around 50 MPH without "lugging" the engine. When I put the 12K# 5er behind it and try to shift to 6th at 50MPH, the RPM is too low, the EGT climbs fast, and the truck will not continue to accelerate hence "lugging" the engine. I like to compare it to the relationship of horsepower and torque. The cummins doesn't develop peak horsepower until higher up in the RPM, something like 2800 while the max torque is on the low end around 1600. If you are needing horsepower to accelerate (pull a hill), you need horsepower (more RPM). The automatics don't have to worry about choosing a gear, that is why they are called automatics.

MnTom

The easiest way (for me anyhow) to tell is that if you are at 1500 rpm and you lightly touch the throttle and the rpms come up without struggling then you are OK. If you are at 1500 rpm and your foot is to the floor and you can't pick up rpms, then you are lugging it. The pyrometer will tell you a lot there too.
Tom

infidel

Tom hit it the way I was always taught, if you can push down on the go pedal and it won't go any faster you're lugging.

rock

I agree to a point. If I have the go pedal mashed all the way to maintain speed going up a hill loaded then I am not necessarily lugging the engine. Now if the boost starts falling off and the EGT goes up then ya, lugging in progress and time to downshift. Still only a manual tranny issue, the automatics downshift on their own.

JyRO

That foot rule with no response deal is true, but I can think of one instance where it is not. I can pull my 5th wheel up Jellico mountain. I'll down shift to 5th and be turning ~2,400 rpm for example while pulling the hill. While in 5th (of 6 gears) at 2,400 rpm, I'm at about 50% throttle to hold speed. If I whomp it down to the floor it won't accelerate ... its doing all it can do. Giving it more throttle is just going to throw heat at it. Is that lugging? I don't think so, the rpm is high enough not to be considered lugging. But at lower rpms, I agree that if you push the pedal and it won't accelerate, then yes, you are lugging.

Asher - You said you think there is a usable amount of rpm below the torque max (1,600 rpm). Well, there is. For example. When I'm pulling my heavy 5'er, and I'm at a dead stop. I start out in the creeper, 1st gear. I slip the clutch only enough to get it fully engaged as close to idle as possible, with as little clutch slippage as possible. If on the flat and level, this works real well. After the clutch is fully engaged I throttle it. From 800 rpm to 1,800 (and beyond before I shift), there is plenty of torque to get all the mass rolling.

Am I lugging it from 800 to 1,600 rpm in this case? No. It works & accelerates very well. So, you think there is useable torque below 1,600 rpm. You are correct. But it is gearing dependant. I can't use the torque below 1,600 rpm in the higher gears because it will lead to the foot rule with no response deal.

And since you have an auto tranny, you're tranny will keep you from lugging below that rpm and will automatically shift you to a lower gear to increase the rpms so that you'll actually get a speed increase when you push down on the smoker pedal. Long winded I know, but I don't think you're going to get ANYTHING written in stone on this topic because lugging is not just a function of engine dynamics, but is complicated by gearing as well.

- JyRO

MnTom

JyRO, what you said is true, but if you look at my post again you will see that I said at 1500 rpm, not any rpm.

JyRO

MnTom - I don't think I was referring to what you said, at least not directly. Mainly replying to Asher.

I agree with your post above 100%.

- JyRO

MnTom

JyRO, No problem. Like I said, you were also 100% right on. Lugging an engine is not as simple as rpm vs. speed.