Crimsonnaire

iTrader: (1)

Hello, everyone.

I was hoping to get some thoughts on the subject of engine lugging and how susceptible to damage a stock V8 LS1 is to it.

First, is there a damaging level of cylinder pressure when you take off in 1st gear with insufficient throttle, causing the engine to buckle and grumble when the clutch is fully engaged for a few seconds? Second, is this pressure comparable to the amount that would be present if you were to take off in a high gear at a low speed, or does the gear selection make an appreciable difference if given the same throttle and ground angle? Also, is it possible to lug an engine without having the obvious buckling and grumbling, such as if you were to go wide open throttle in 6th at 1200 RPM/60mph? If so, then is it also possible for the engine to produce these effects even when it's not under heavy load, and does it also mean that even an automatic transmission cars can also be lugged? In essence, I've been trying to understand if the general consensus on the signs of lugging (deep vibration/grumbling) is part of a process that strictly involves the combustion level/throttle vs. the combustion volume allowed by piston speed/RPM which may or may not be in conjunction with straining the engine with high loads/lugging. Third, is the PCM capable of preventing the cylinders from reaching the pressure threshold? And finally, what kind of damage would a stock LS1 V8 exhibit if subjected to the first case above (1st gear at low throttle) over long term?

Any clarification on this matter is greatly appreciated.

wagonwes

Bump for this thread. I have very often wondered the same thing. I'm looking for some opinions or knowledge on this too.

I am pretty sure that taking of in first gear from a stop is not really lugging (it kind of is, but it's effects are so small.) It is more or less the clutch grabbing and bringing the engine from no-load to part-load. Lugging is more of what you described later, such as a high gear at a low speed.

Lugging is not necessarily throttle position related per se, it is more mass air flow related. I know you mentioned a hill in your question, so obviously going up it would be more of a load compared to level ground at the same throttle and gear.

I believe lugging is basically your car not being able to support the torque requirements at *that* point in time. Which is why automatic transmissions shift off manifold vacuum and throttle demand (and a whole slew of other things.) So, it is not likely that an auto could be lugged.

Then again, I guess it depends on what the definition of lugging is. I have tried searching google for "definition of lugging" and could not find anything technical at all.

Deep vibration and grumbling is a sure sign of lugging, but I am positive it happens before that. Kind of like detonation can happen even though the knock sensors might not be able to pick it up. I don't know what you mean by combustion level and combustion volume either, could you be a little more specific? Do you possibly mean burn rate?

I know I didn't answer all of your questions, but this is just my speculation. If you really want to get fancy (and spendy) there is a website called www.TFXENGINE.com. I called them a while ago and asked them for pricing. It is 9500ish for the spark plug cylinder transducer, signal conditioner/amplifier box, and software. It seems like a lot, but I can almost promise you will not find anything cheaper. I work for an engineering consulting firm in powertrain and development, and our pressure transducers alone start around 10000. Unfortunately, we don't have a chassis dyno (only 15 engine dynos) so I can't monitor the effects of engine lugging.

All in all, you have put up an excellent question, and I hope others chime in.