Is there a Standard Definition of Lugging an Engine?

[XR250]

Title says it all.

Is it something like, "when X harmonic gets excited to this frequency" etc?
Or is it more just a feel thing.

 

[Tmoose]

Once upon a time I believe I read that one clue is if the throttle is opened more, the engine can/will not increase the vehicle speed.
Probably also had a low rpm qualification, cause I guess power limited top speed is not included.

I was surprised when our new-to-us approx 10 year old, good running Camry 4 cylinder with automatic transmission and 60 kmiles when left in "D" chooses to operate at 2 krpm or so accompanied by a slight booming sound.
I seem to recall a rental ( Chrysler 200 ) several years back that did something similar.

 

[XR250]

I typically like to run my cars at low RPM's (I drive stick shift).
My new Mazda3 has cylinder deactivation that kicks in around 1,700 RPM. If I run it less than 2k RPM, I feel an annoying vibration as it runs on 2 cylinders. Over 2k the vibration disappears even if it is still on 2 cylinders. The car has a gear suggester that will want me to hold or shift all the way down to 1,400 RPM.
Unfortunately, no one makes a tune for Mazda's that will defeat this.

 

[GregLocock]

No. On a dyno you run a full throttle sweep from idle speed to redline. You ae probably trying to avoid driveline resonances rather than anything fundamental to the engine itself.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[BrianPetersen]

As far as I can tell, this is completely qualitative.

Clutches (including lock-up clutches inside torque converters) contain vibration dampers that are only capable of absorbing so much crank-speed irregularity. If the revs are low enough and the torque request is high enough to overwhelm those, you're going to feel it. One of the things done inside modern automatic transmissions to boost their efficiency has been to install serious vibration dampers so as to allow the revs to be brought further down at full torque with the converter locked before those vibrations start to be felt. (old skool lock-up clutches weren't even strong enough to hold full engine torque at any revs)

Same goes for the engine mounts.

I'm sure the calibration folks will discuss knock thresholds and mitigation - the need to delay ignition timing at low revs and/or run rich near full load to forestall knock, even though it also cuts torque output.

My motorcycle engines are unhappy below 4000 rpm if you ask too much of them, and they'd rather see 5000 plus, and for that matter, they'd rather see 7000 plus. They don't really get on the cam / on the pipe (exhaust) until they're spinning fast.

If you're clever with the accelerator pedal while climbing a hill, the Pentastar 3.6 V6 in my van can be dragged down to 1100-ish rpm in 6th gear at (near as I can tell) full torque with the torque converter locked. Obviously if you ask any more of it whatsoever, it does a downshift. That isn't in a favourable part of its torque curve, but in the interest of fuel consumption, it tries to stay in higher gears and lock the torque converter as much as it can.

 

[XR250]

Got it - thanks

 

[gruntguru]

It would be useful to consider the BSFC Map for the engine in question and the optimal operation line (the best place to be for any given power requirement). Link Operating above this line might be considered "lugging".

je suis charlie

 

[hydrae]

Lugging used to be really bad as the oil pumps (or other methods such as slingers) were fixed size and a low rpm
and heavy load would not float the bearings and cause damage.
Modern engines have better oil control to avoid this.

 

[GregLocock]

How old is this? My experience is with 1978 onwards engines on dynos, and as I said, we ran full throttle from redline down to idle.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[TugboatEng]

Subaru in the 2000's used to have issues with breaking ring lands on their turbo engine. Short shifting seems to be a common trait of Subaru drivers. They always put loud mufflers on their faces so you could hear them doing it. I seemed like they were proud of their cars and thought they were preserving them by keeping revs low. I feel like this caused a lot of the broken lands.
They were also obsessed with break in and warm up.

 

[GregLocock]

I worked on the first of the Honda engined Triumphs. The engine guys phoned Honda to ask what the break in schedule was for the new engines. Muffled Japanese, followed by "You could idle it for 5 minutes".


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[TugboatEng]

Same with Caterpillar. After an overhaul it's 30 minutes at full power then remove and inspect one oil filter.