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Old 06-04-2010, 11:47 AM   #1
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lugging the engine

OK, we're not supposed to lug the engine.
Why, how does it hurt the engine?
And what constitutes lugging? Revs too low for the gear, but how low?

Sorry to be so ignorant.
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Old 06-04-2010, 11:52 AM   #2
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I would not call it ignorant...I think it is a perfectly relevent question.
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Old 06-04-2010, 12:13 PM   #3
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That is indeed a good question. I've keep wondering if people really do know WHY lugging is bad for a car, rather than just saying that its bad.

You should go here: http://www.standardshift.com/forum/viewtopic.php?t=5567

Its a good thread on the subject.

-tran
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Old 06-04-2010, 12:27 PM   #4
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Quote:
Originally Posted by pierre shags
OK, we're not supposed to lug the engine.
Why, how does it hurt the engine?
And what constitutes lugging? Revs too low for the gear, but how low?

Sorry to be so ignorant.

You'll know it when you do it. The car will buck like a bronco and make some awful lurches and noises. Press the clutch, downshift and try again.

Can't say this has happened recently, and I've never once looked at the tach -- but I'd guess in the 1200/1400 RPM range.
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Old 06-04-2010, 03:49 PM   #5
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The concept is pretty simple if you think about it. Shortly after startup all of our M96 moving parts are ideally floating on a thin coat of oil. Minimal metal to metal contact, minimal wear. When you put a heavy load on an engine at low rpm such as hard acceleration or climbing a hill you risk exceeding the ability of the oil to continue floating the parts and you get metal contact and excessive wear. Because the oil pump is tied to RPM, the lower the RPM the slower the oil replenish. When the engine load exceeds available oil replenish damage is done.

The severely lugged engine (bucking bronco) has gone far beyond overloading available lubrication, bearing surfaces are all on metal, and the motor will not turn over well enough to enable complete combustion causing detonation and further engine damage.

The simple solution is downshift to increase your oil replenish rate, float the internal moving parts and support the increased load. Our motors seem to be more sensitive to low RPM loading than most so unless I am at idle, coasting downhill, or approaching a stop with no engine load I rarely run my RPM below 2000.
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Old 06-05-2010, 12:21 PM   #6
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In general, smaller motors are easier to lug, ie not much torque down low in the RPM range.

It much harder to lug a Corvette for example, as they make lots of torque way down low in the range.

Either way, it is a bad thing, as your car will tell you pretty quickly.
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Old 06-06-2010, 05:06 AM   #7
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when my car is cold especially, I shift below 2k rpms and never hear an irregular engine sound.....i dont watch rpm too much unless its at the max side, i just listen for the engine
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Old 06-06-2010, 05:20 AM   #8
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why would someone drive their car like that ?
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Old 06-06-2010, 06:46 AM   #9
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Other than starting off in first gear, my engine does not see anything below 3000 rpms if I can help it.
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Old 06-06-2010, 03:50 PM   #10
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Quote:
Originally Posted by landrovered
Other than starting off in first gear, my engine does not see anything below 3000 rpms if I can help it.
Here, here, Landrovered! The S 6-speed and the perfect pedal set-up in the 987 make rpm matching downshifts soooooooo pleasurable, I look for excuses to shift!
Now that my Schnell short shifter is completely broken in, it makes it that much more enjoyable.
We did a 1700 mile vacation last weekend (four days) and I found myself in the way in traffic (going too slow) on the homeward bound trip because I didn't want it to end!
The roads around Harper's Ferry, WV were great!
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Old 06-06-2010, 11:54 PM   #11
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Why, how does it hurt the engine?

A long time ago, I had a master mechanic tell me that he could always tell an engine that was lugged when he tore it down, the tops of the rod bearings would always be worn out. He said that there should be no way the rods would wear that way unless the engine was lugged.
I went to Automotive school for a year when I was a kid. My instructor said the definition of lugging is: "Anytime you open the throttle and the RPM's don't increase, you are lugging"
I've never had a car with a rev limiter before the S, I sure get a lot of use out of it now. Don't think I will have any issues with the tops of my rod bearings wearing out.
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Old 06-07-2010, 10:31 AM   #12
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you'd probably get a better answer with a quck Google search, but here's a few random comments.

Oil pressure is RPM dependant, so low RPM lugging has less pressure to form an oil "wedge" to protect the bearings. Compounding this is the fact that large throttle opening allow a large air/fuel charge, which means a bigger "explosion" pushing down on the piston, which is transferred to the bearings. The engine is also prevented from revving freely, because it's lacking the mechanical advantage of torque multiplication lower gears provide.

Hey Kurt, any particular roads you recommend? I may be going to Summit pt. WV to watch some racing.
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