Engine Lugging

Discussion in 'GS Boxers' started by Aurelius, Nov 12, 2002.

  1. Aurelius

    Aurelius Long timer

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    The claim is often made that lugging is destructive to engines. I've asked many people about this, including two experienced motorcycle mechanics, but no one thus far has been able to provide any reason to think its true. In fact, both mechanics I spoke with think that lugging does absolutely no harm to an engine. Does anyone here know differently? I'm looking for something a bit more convincing than, "Well, I heard somewhere that...", or "Everyone says it does", or similar remarks. Anyone have a serious explanation they'd care to offer?
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  2. Chopperman

    Chopperman I am dead

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    1) it promotes pinging. you think this is good on the motor?
    2) you hear that noise? that is the conrod being battered about. real good for bearings and pistons.
    3) fuel is not entirely burnt. lots of lovely black crap packed in the compustion chambers.
    #2
  3. Hankth

    Hankth Been here awhile

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    I think there may be some confusion on the term "lugging". If you run the engine down to an rpm that doesn't allow you to gently roll on the throttle and gain speed smoothly, you're lugging. If you run the engine down to a lowish rpm, but can increase speed without bucking, pinging, etc, your'e not really lugging, your just out of the power band, but doing no harm. This rpm can vary with wether you are going uphill, downhill, or on the level. Hope this helps
    Hank
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  4. Aurelius

    Aurelius Long timer

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    Pinging will certainly cause damage eventually, but I've never noticed any pinging or unusual sounds when lugging an engine. All that happens is an increase in engine vibration. I don't make a habit of lugging the motor, but I am curious as to what is happening inside when it does occur.
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  5. Chopperman

    Chopperman I am dead

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    re-read hankth's post
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  6. Aurelius

    Aurelius Long timer

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    Does lugging necessarily cause pre-ignition (pinging)? I'm well aware of the metalic rattle associated with pinging, but have never noticed that sound when lugging the engine. The phenomenon I associate with lugging is a dramatic increase in engine vibration when opening the throttle at very low rpms. The only time my bike exhibited pinging was when I used 91 octane gas (instead of the usual 93), and whacked open the throttle in top gear. There was no resulting increase in engine vibration, which suggests to me that lugging and pinging are two different things.
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  7. Chopperman

    Chopperman I am dead

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    put it in 6th and pull away from a stop. does that sound good to you? that's lugging. dont do it. got it?
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  8. iillyyaa

    iillyyaa Adwrenchurer!

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    Technically, true. But former, among other bad things, may cause latter.

    Let me give you an analogy:

    Getting wedgies is unpleasant. Getting wedgies and annoying people are two different things. Annoying people may cause wedgies. Just because you don't get a wedgie every time you annoy someone doesn't mean that it's OK to annoy people. That's because, aside from a wedgie you may get a wet willie, a swirlie, a nuggie, an eye poke or a nose squeeze.

    Get it? It's really that simple. :):
    #8
  9. Captain PHX

    Captain PHX Western Adventurer

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    You asked for it, Andrew!:rofl

    Outstanding, Jinx!
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  10. Rad

    Rad Just me

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    :super

    Post of the week award goes to Jinx
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  11. Zollo

    Zollo Long timer

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    "So we need some flywheel, but as little as possible since everyone seems to have agreed that pulling the front wheel in the air in city traffic is, as a characteristic, far preferable to a bike that will plonk along in tight off-road conditions. And we need to accelerate the whole porcine mass of the GS and rider".

    Jinx



    In a nutshell, Ladies and gentlemen!


    Zollo
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  12. Curmudgeon

    Curmudgeon Enjoying the ride

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    When I'm practicing trials balancing on my stop and go commute, the 1150gs engine can idle at 1400 rpm with minimal throttle and to my ear no lugging. Yet, if I were to crack the throttle too quickly it's lug city. So low rpms (below 3500 rpm) require delicate throttle increases, or it's lug city. But, above 3500 rpm you have a free hand, so get all squidly with that German farm implement, and things will never be quit the same again. Having to live with all the contradictions of the GS is charactor building enough, and then becoming attached to the beast is almost too much. Almost!

    Patrick
    #12
  13. Stephen

    Stephen Long timer

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    I say "post of the bloody month"!
    Well, fortnight, anyway. After all, I must hold Jinx in continued contempt for grabbing all those Guzzis at once.

    As to lugging, here's a little different way to look at it:
    Modern engines run sweetly and sonorously up high. Why not keep'em up there where they're happy?
    #13
  14. Aurelius

    Aurelius Long timer

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    But no one even remotely suggested we deliberately lug our engines. The question was why lugging is considered harmfull. As for why we shouldn't just run our engines at high rpms at all times... well, perhaps its just me, but keeping my bike in third gear at 75 mph doesn't make much sense to me. :confused
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  15. Chopperman

    Chopperman I am dead

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    I dont see why this is so difficult.

    the motors run great up near redline. lots of power. ANd great for the heavy load acceleration. Once at spoeed you are under a light load and it is safe to go up a gear to lower the RPM for comfortable cruising. But when accelerating again, drop a gear. It's as natural as farting and feels as good.
    #15
  16. kevbo

    kevbo Rubbery-Lip Flappin' PHI

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    Excellent post Jinx. Agree on all points but the one quoted above, and mostly I agree with that too.

    Oil pressure is needed to supply oil to the bearings, but the actual load is taken by a wedge formed by hydrodynamic drag between the oil and the moving part of the journal bearings....Much the same way that the weight of a waterskier is supported even though the surface of the lake is not pressurized at all.

    Like the water skier, if the speed is too low then the support fails, and you get metal to metal contact.

    There is a range of surface speed where this works, so an engine designed for a high redline (small diameter bearings) will lack speed for correct bearing operation at low rpm. Similarly, high rpm engines have short strokes, so the piston skirts run in the speed range where the skid on oil film, rather than digging in.
    #16
  17. Stephen

    Stephen Long timer

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    Exactly.
    I wouldn't lug an engine even if it wasn't bad for it. It's bad for me.

    And you don't have to say "Excuse me" (or even "Bad dog!") when you downshift.
    #17
  18. Captain PHX

    Captain PHX Western Adventurer

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    For me, Jinx summed it all up with the above quote...higher than necessary levels of stress on internal moving parts.
    #18
  19. iillyyaa

    iillyyaa Adwrenchurer!

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    I'm with you here.

    I know that lugging is bad. Jinx explained everything that I understood about lugging. I don't do it, I wouldn't recommend doing it, etc. No problem here.

    However, revving high means running more engine rotations per unit of distance. So, for example, if you are cruising at a constant speed, you have a choice of several gears that are appropriate for each speed. I would choose the highest of those gears for the simple reason that I want my bike to last me a long time. All the contact points for running parts (bearing races/barrels/needles, compression rings, cylinder bore, etc.) are points of wear. The amount of wear is proportional to the distance travelled by the parts making contact relative to each other.

    Here's an experiment:
    I ride for 1 mile at 60 mph in 5th gear at 3500 RPM (for example), the crank will make 3500 revolutions.
    You ride for 1 mile at 60 mph in 3rd gear at 5000 RPM, the crank will make 5000 revolutions.
    That means that we both travelled the same distance in the same amount of time, except that my engine got 70% less wear than yours.

    Gas mileage is also a factor.

    So, don't lug. Ride at the lowest RPM that satisfies your power requirement. (i.e. if you are accelerating - use lower gear, if you are cruising - use higher gear.)

    Common sense, really.

    P.S.: Some of you know (of) Fred who has 630,000 miles on his R60/7. I hardly think he exceeds 3000 RPM on that bike. He's got the original bottom end and only went through 2 sets of heads and valve gear. What more can be said?

    --
    Ilya
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  20. Curmudgeon

    Curmudgeon Enjoying the ride

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    You say tomato, and I say tomato.

    So, wouldn't that be 30% less wear, or 70% of the wear, but NOT 70% less wear.

    Patrick
    #20