Lugging -- what's that sound?

[rationull]

Originally Posted By: Hokiefyd

This is how I define "lugging". It's at an RPM that's barely enough to keep the engine running at a reasonable speed for the load (usually 1500 rpm or less) and you get a severe grinding sound with an associated vibration from the engine that feels very much like bearing surfaces making contact with each other.

This is probably the reason (true metal contact) for "it's bad for the engine" when truly lugging an engine.



1500 RPM sounds like an awfully high speed to be too low to maintain adequate oiling and get metal to metal contact though...

 

[ltslimjim]

Isn't the lugging(choose an RPM) relative to what engine/trans are working together?

For instance, the optimum fuel economy for this little Civic is anywhere from 1,500 RPM-2,200 RPM or so; this is in part where the lean-burn range functions in.

 

[SteveSRT8]

Good point, and it's also relative to engine design.

And forget about bearing contact in any healthy engine. You might damage some old clunker but any correctly running engine will never experience any mechanical damage from low rpm highly loaded operation.

Did anyone look at diesels? They routinely lug the [censored] out of them in normal operation.

 

[Shannow]

And they have really really big bearing surface areas, large journals, and thick oil.

 

[SteveSRT8]

But you missed this: Diesels develop massive torque at low rpms, n/a gasoline motors do not. Hence the lugging analysis must carefully consider the platform first, instead of huge generalizations about completely unproven rod bearing wear.

Also, not all diesels are made by caterpillar. I've seen many car diesels that I would not say had overly large bearings/journals and many do not use thick oil.

 

[FZ1]

Who are we gonna believe? You,or our lyin' eyes? Lugging can be detrimental to your drivetrain. Common sense. If lugging were harmless,we would only have 1 gear in our gearbox..........Overdrive!!! Now,I'm beginnin' to wonder about that 12.79?

 

[NateDN10]

Originally Posted By: FZ1
If lugging were harmless,we would only have 1 gear in our gearbox..........Overdrive!!!

This is silly. Clutches would be burning up left and right if forced to slip until the engine could road speed allowed the engine to be over idle speed.

 

[FZ1]

Clutches are part of your Drivetrain. You make my point.

 

[Quattro Pete]

Originally Posted By: FZ1
If lugging were harmless,we would only have 1 gear in our gearbox..........Overdrive!!!

I think you meant "if lugging wasn't harmless..."

 

[mechtech2]

Originally Posted By: FZ1
Who are we gonna believe? You,or our lyin' eyes? Lugging can be detrimental to your drivetrain. Common sense. If lugging were harmless,we would only have 1 gear in our gearbox..........Overdrive!!! Now,I'm beginnin' to wonder about that 12.79?


No.
Multiple gears are primarily to help acceleration.

 

[SteveSRT8]

Originally Posted By: FZ1
Who are we gonna believe? You,or our lyin' eyes? Lugging can be detrimental to your drivetrain. Common sense. If lugging were harmless,we would only have 1 gear in our gearbox..........Overdrive!!! Now,I'm beginnin' to wonder about that 12.79?



Hahaha, no need to wonder. It's on youtube!

No one said it could NOT be detrimental, we are saying that in most any modern car it won't hurt anything.

You should hear my car turn a 20 mph corner in 4th gear and 'lug' away at 900 rpm with the converter locked and all. Of course i prefer second gear at the 6600 rpm limiter, but the factory program is always looking to 'lug' the engine.

 

[FZ1]

But you have an AT. The OP was talking re lugging an Mt. The point is: lugging a manual is detrimentental to your drivetrain. Anytime,your Drivetrain is "struggling",making noise,etc.,from too high a gear selection,at too few rpms,that's not good.

 

[ltslimjim]

Is there a fine line between 'minor' lugging and 'engine rattling because of lug'?

 

[rationull]

Originally Posted By: FZ1
But you have an AT. The OP was talking re lugging an Mt. The point is: lugging a manual is detrimentental to your drivetrain. Anytime,your Drivetrain is "struggling",making noise,etc.,from too high a gear selection,at too few rpms,that's not good.


To be fair, in his example he said the TC was locked, and an AT with a locked torque converter is practically the same as an MT with the clutch plate engaged for the purposes of this discussion. The only thing the AT isn't susceptible to is the driver's clutch modulation.

 

[rationull]

Originally Posted By: ltslimjim
Is there a fine line between 'minor' lugging and 'engine rattling because of lug'?


There's definitely a line .. and the case I was really talking about here is the "bogging when starting off" case, which is not the same as low frequency vibration from cruising or lightly accelerating while below the power band.

 

[SteveSRT8]

Originally Posted By: FZ1
But you have an AT. The OP was talking re lugging an Mt. The point is: lugging a manual is detrimentental to your drivetrain. Anytime,your Drivetrain is "struggling",making noise,etc.,from too high a gear selection,at too few rpms,that's not good.


OK, not good. Anything other than opinion, because there's no way that one blanket statement can apply to all the different drivetrains in use!

 

[FZ1]

Thanks. I was just speaking to the Ops manual transmission. I've never heard of "lugging" an AT.

 

[Errtt]

I've lugged some solid mount Harley motors and that pounding knock noise comes from within the motor - not the motor mounts being unable to absorb - I can hear hear it right at the cylinder heads - I've done it with an ear dipped down beside the engine.

 

[SteveSRT8]

Originally Posted By: FZ1
Thanks. I was just speaking to the Ops manual transmission. I've never heard of "lugging" an AT.


Well, locking torque converters have been around a while, and with the gas saving strategies in use they will routinely lock up under 1000 rpm in my car. Plus with many slushboxes you can force them to upshift manually very early, thus loading up that precious drivetrain at low rpm.... seems similar at least!

Jeez, I hope you're not another one of those 'stick shift' snobs!

 

[dailydriver]

Originally Posted By: FZ1
Anytime,your Drivetrain is "struggling",making noise,etc.,from too high a gear selection,at too few rpms,that's not good.


When you say it is not good for the "drivetrain", are you talking about forward of the flywheel only, or are you saying it could also hurt components aft of the flywheel??