Just to follow up on my earlier question, it was in relation to very firm statements such as this one:
Quote:
Originally Posted by ssjr0498 What you should "NEVER" do is to let a new engine "get bogged". If you let the engine bogg (a couple of times is fine), on a regular basis, that's it!! Forget life/performance out of it. |
That made me wonder what bogging/lugging really is and why would it be so damaging to an engine? I think I begin to understand what bogging/lugging is.
I liked this definition quoted by one of our members:
Quote:
In technical terms, lugging is when throttle input does not cause any accleration.
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In itself this is where part of the problem (or the understanding of the problem) already begins. Because this situation can occur across a huge wide range of engine loadings. You could be barreling up a hill, in third and revving 4500rpm and pushing the accelerator and no acceleration happens, i.e. lugging.
Or you could be going up a different hill in third revving 1500rpm and pushing the accelerator won't do a thing. In both scenario's you are likely to experience the same symptoms, but maybe with somewhat different severity.
So what is it that under these sort of condition is, apparently so damaging to an engine. I don't think I have heard a good explanation yet.
Yes, your FE will go south, yes you will belch out some soot, but neither is particularly damaging as such, or at least no permanent damage.
It has been suggested that the crankshaft would be loaded up heavier. But how can we be sure it is so. Roughly speaking the crankshaft, bearings and conrod loading is a function of RPM and fuel injected. But its also obvious that combustion condition during lugging are not particularly good to put it mildly. So how do we know that essentially the force on the piston during lugging is greater than under normal full load conditions? I don't think we do, and my gut feeling is it isn't either. (But I'll happily let someone proof me wrong or otherwise)
Short version, I think it's largely a myth, stemming from some sort of better safe then sorry type of approach.
The damage (if any) will depend heavily on the condition under which lugging happens (i.e. what rpm, what loading etc) and for how long and how often.
Here are my thoughts what could get damaged over a long period of time:
Bad combustion can also effect the piston, piston ring, cylinder liner lubrication, so expect some additional wear and tear there.
As mentioned by various members, during lugging you feel the engine sort of shuddering. As I stated before, I'm not so sure that that will immediately cause problems with bearings. But some of the gears, i.e. transmission, gear box etc. it might. There is a phenomena called teeth clattering and it is where two meshing gears don't maintain sufficient pressure to keep optimum lubrication going. It tends to happen in gear boxed that don't get loaded up properly, say a PTO shaft that is running for a long period with no load. I've had such a situation on one of the gearboxes of a ship with (near) catastrophic result.
There might be a few other areas as well. But, without real data it is a bit guessing in the dark I'm afraid. Never the less, the old better safe then sorry is always a save bet to play. Even if we don't understand why.
Jeroen