Why is Lugging Engine Bad?

[Friend]

Can anyone explain why lugging the engine is bad and how it hurts the car?

By the way, I think I somewhat lugged the engine during break in because I was shifting at around 1500 rpm. I thought I was doing the car a favor, until I heard the lugging the engine was bad. I did not open the throttle much however.

Thanks in advance.

[charlton_chow]

I would like to know what lugging is

[PureLife]

Lugging is caused by predetonation ... the fuel doesn't burn at an efficient rate, but rather explodes at the wrong time. This causes wear on the cylinder walls and will eventually leads to you needing a new engine. If you wanna try it (once in a blue moon wont damage anything, put it in 5th at 20mph and give it some gas ... it usually sounds like someone is throwing rocks under your hood ... everything starts to rattle and shake).

As for the original poster ... most manufacturers tell you to go no higher than 4000rpm during break-in and to vary your rpm and speeds ... by shifting at 1500 rpm, not only did you lug it a lot, but you didn't really help it with anything.

[Prodigal Son]

I'm pretty sure that most people who think they have been lugging their engine really have not been lugging it at all. I'm not even sure that modern ECUs and knock sensors would let the engine lug. My experience with the Jetta so far has been that it either runs or stalls. I have not heared it lug (even when I accidentally took a corner in 4th instead of 2nd).

Putting a load on an engine at low RPM will make it growl, but growling is not lugging. Lugging is irregular. If it growls and goes it is not lugging (at least in my understanding of the matter).

[Daywalker]

does lugging include putting it in 4th or 5th at like 5-10 mph and letting it jerk a little then stall out? I've done that a few times to freak people out in "haunted places"


sometimes my car jerks when i have a sloppy 1st to 2nd shit or if I mess up in first, but i think its because the gas is so touchy my foot quivers on the gas and causes it to osilated or something. I dunno how to explain it.

[Hatchman]

Putting a load on an engine at low RPM will make it growl, but growling is not lugging. Lugging is irregular. If it growls and goes it is not lugging

Still, even this can't be too healthy huh.

[Prodigal Son]

Putting a load on an engine at low RPM will make it growl, but growling is not lugging. Lugging is irregular. If it growls and goes it is not lugging

Still, even this can't be too healthy huh.

I don't know. I've never heard a convincing explanation of why it would be bad for it though. Maybe those who say it is bad are confusing it with lugging?

The growl is simply the engine note at a lower frequency due to lower revs. Some may find the noise unpleasant, or even assoiciate it with an animal growl and assume (unconsciously) that if an animal is unhappy when it growls then a motor must be too.

Can anyone give a reasoned and authoratative argument as to why or why no it would be bad simply to run an engine at low revs (assuming no lugging)?

[Hatchman]

Can anyone give a reasoned and authoratative argument as to why or why no it would be bad simply to run an engine at low revs (assuming no lugging)?

If the growl thing is what I think it is, it's the same as being at really low revs in 4th let's say, and getting no "go" when you want to accelerate. In the VW, the growl was there (then again, that thing always growled LOL), but in the FiT, I get the hesitation without the growl, indicating I should've downshifted instead of just thinking about it. I hate that hesitation, which is why I downshift more often than I used to in city driving. But anyway, I think the worst thing about the growling hesitation is wasting fuel when you try to hard to accelerate from very low revs. Also, you can cause a hazard on the road by being somewhat of a sitting duck while struggling to accelerate away.

[Prodigal Son]

Agreed. Hesitation is bad. Not necessarily bad for the engine (wild ass guess that the hesitation is caused when the ECU does not let the engine lug), but bad for your progress down the road.

The Jetta 2.5 engine, which is tuned for low-end torque, will growl and go, without hesitation, though certainly without a lot of zip, at absurdly low revs, and will recover into the power band fairly quickly -- generally more quickly than I could pull off an unanticipated downshift. This car is very forgiving -- which, as I have said before, is either a good thing or a bad thing depending on my mood.

Your Honda engine, if it is true to form to what I have heard about Honda engines, is more tuned to the high end, so it may have little growl and go range. Then again, the notion of "growl" is subjective. Smaller engines have higher-pitched voices, so the low-rev-but-happy range of your engine may simply not create a note that registers on your ear as a growl.

Suffice to say that, in my view, it is how the engine that behaves that matters, not the note it produces. If its voice is regular, regardless of the pitch, and it responds to the throttle, it is not lugging, and all is well.

At least, that is how it seems to me.

[DW10+BE4/5L]

The engine vibrates more at low speeds so that might be one reason why it's bad. At least it feels like it vibrates more. It's bad for everything that's attached to the engine, accessories and transmission. I don't know _how_ bad. Could you for example always cruise at 1000 RPM, assuming that there was enough power, and nothing would break earlier than if you cruised at 2000 RPM.

[Prodigal Son]

The engine vibrates more at low speeds so that might be one reason why it's bad. At least it feels like it vibrates more.

Low range vibrations travel more and are more easily felt than high range vibrations. That is why the music coming from the neighbours a few doors down just sounds like a deep base thumping with none of the melody or high notes reaching you. But just because they are more easilly felt and heard does not in itself mean that they are worse for the engine.

Again, I'm not asserting that it's not harmful, because I don't know. I've just never heard an explanation that convinced me. After all, diesels vibrate at a lower range, sound positively unhealthy at idle, and yet last far longer than gas engines.

[Tinton]

I haven't been given any definite reasons for lugging to be bad either. What I have heard though is that low rpms but a very large strain on the engine. To get an idea of what I mean: when my car was overheating I was asking of ways to test if it was a headgasket. Of course you could do a compression test, but the car was stuck in my garage (it'd overheat in under a mile of driving) and no one nearby could help me with that. 1 guy, who has worked on cars for years, told me to take the car out and put it in 4th gear, at about 1500 rpms and floor it. Supposedly, at that rpm it'd put a massive strain on the engine and it'd lose more compression into my cooling system, which would cause it to overheat very quickly. Pretty much everyone I know, when asked why lugging is bad, they say its because it puts a great strain on the engine.

[Prodigal Son]

I haven't been given any definite reasons for lugging to be bad either.

We know why lugging is bad. Lugging is predetonation which throws the pistons off course and scars the cylinder wall. Merely running at low RPM is not lugging. The question is, is merely running at low RPM bad for the engine. "Puts a great strain on the engine" is not an explanation. At low rpm, an engine is not making much torque, so if you try to accelerate quickly, it will not be able to respond. In some sense this is putting a strain on it, but really all you can do to an engine is dump fuel and air into it, and if that generates enough torque it goes and if it does not, it doesn't go. What parts exactly are being strained?

[vios]

I haven't been given any definite reasons for lugging to be bad either.

In some sense this is putting a strain on it, but really all you can do to an engine is dump fuel and air into it, and if that generates enough torque it goes and if it does not, it doesn't go. What parts exactly are being strained?

Assuming the same amount of air-fuel mixture, then the same amount of energy is produced. If the engine is at the correct revs, then the energy of detonation is transferred by pushing down the piston, the piston moves at the appropriate speed such that the burn is complete by the time the piston is at its lowest point. The cylinder volume is at maximum, and the cylinder pressure drops.

If the revs are too low, then the downward movement of the piston may not be fast enough such that the burn is complete but the piston hasn't gone down completely. The cylinder volume is not at its maximum, so there is build up of pressure. That pressure has to be transferred somewhere (presumably to the cylinder walls, etc) or at least converted as more heat.
That, I presume, is the concern for damage when dumping the gas at low revs.

But as you mentioned, modern cars have intelligent ECU's. So it would either adjust the air-fuel ratio or cut off the fuel completely when the throttle is mashed at low revs.. The engine either goes, hesitates or stalls. But I don't think it would lug that significantly. Maybe with old cars, this is a concern.

Tony

[Hatchman]

Damn, this Tony fella is good.