Engine Lugging...

Messages
349
Location
Quebec, Canada
...how does the oil protect the engine during this situation? In fact, can anyone explain the consequences of prolonged engine lugging? I lug my engine probably around 5 times per week (stupid hydraulic clutch systems [Mad] ). So, I guess the questions are: - How does oil protect the engine in this situation? - Is there a particular additive in the oil that helps? - What engine internals gets worn down prematurely? - Does it affect other non-engine related components? - How in the world do I prevent this!?!?!? Thanks, Oz
 
Messages
3,202
Location
Far North East Texas
Oz, careful there! Lugging an engine is *Very* hard on the bearings. Just downshift sooner. If pronounced enough, it's also hard on driveline U-joints in RWD. My guess that when lugged, the EP additives become very important. Since engine rpm is low, oil pressure is probably on the low side too. Repeat: lugging is very bad for your engine & vehicle.
 

MolaKule

Staff member
Messages
21,725
Location
Iowegia - USA
I don't think occasional lugging will do much damage. Howver, it should be avoided if possible. As I understand it, lugging is low engine rpm caused by a mismatch in vehicle/engine speed, and improper gear slection under high loading conditions. Lugging creates "shock" loads to the piston and crankshaft. You also have a momentary heat rise, since the coolant moves slower than normal. How does oil protect the engine in this situation? By providing lubricating films and cooling. - Is there a particular additive in the oil that helps? Anti-wear and Friction modifiers certainly help here, since your oil pressure is probably too low to keep hydrodynamic lubrication going. A good boundary additve as backup certainly helps. - What engine internals gets worn down prematurely? I would say the wrist pin, the connecting rod, and the large bearings in the engine get stressed the most. - Does it affect other non-engine related components? The timing chain or timing belt is also seeing these shock loads. And you will get surges in fuel delivery since the computer is attempting to compensate. - How in the world do I prevent this!?!?!? Get the clutch adjusted and make sure the rpm's are high enough to produce a sufficient amount of torque to move the vehicle. I had rather burn clutch material than damage internals.
 

Al

Messages
19,206
Location
Elizabethtown, Pa
Lugging is extremely hard on your bearings. That is because you are creating max horsepower at that given rpm which translates into a very high bearing load on the big end and small end rod bearing. That coupled wwith the fact that you have a very low rpm and you totally violate the classical bearing equuation: (N x V)/L, where L = Load, V= viscosity, and N= RPM. As this value gets lower in magnitude you drift into the mixed film and into the boundary lub conditions. Needless to say a heavier oil (Higher V will help).
 

The_Oz

Thread starter
Messages
349
Location
Quebec, Canada
Stuart -> I have a FWD. It's not that I'm downshifting later, I lug engine normally when accelerating, accelerating on a hill, heavy loads from a complete stop OR when the car is around 10km/h and I engage to 2nd instead of rev-matching to 1st. MolaKule -> Once again, [HAIL 2 U!] Patman -> Automatics are boring! [Big Grin] Al -> Based on your statements, I guess this is another plus for the Delvac 1 5W40 that I'm using instead of 5W30. Woohoo! Widman -> I think the adjustments required is not in the car, but me [Wink] Thanks Guys, Oz
 
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