Topic: Lugging the engine

[tigercat]

I know trying to climb a steep grade in 5th gear with the accelerator floored and the engine spinning at 1,800 RPM isn't good for one's engine. Why is this? What specific strains are put on the engine when you lug it?

[barrie1]

Its more then just the engine you are hurting, the clutch won't be very Happy about this either. The Crankshaft is taking on a lot more torque as well. Not a good habit to get into.

[articsteve]

Technically you are going to torsion your crank and the individual pistons will then become very so slightly out of phase and the cylinder head temps will rise and you will get detonation which creates an unwanted shock wave through the motor.  It's a bad practice and it probably costs more in gas.

I'm always trying to correct my wife about doggin it up hills. I tell her that nothing below 3000 rpm up hills.  She always replys that she was unaware of the issue and its the first time she's heard about it.  It's like a movie that plays the same scene over an over again.

[21Rouge]

Great topic guys.

I have a 5 speed simple 4 cylinder.

I have driven a 5 speed for 20 years but while driving the other day my friend who was a passenger made the comment that I was in the wrong gear too often; specifically too *low* a gear at any given time. Thinking about it later I bet I do upshift well after I could have ie my rpms are much higher than they *need* be to be able to properly shift to the next higher gear. Until now I would change around 3000 rpm. I am sure that is mechanically ok but maybe I could do better if I consider fuel economy. I guess I always thought that changing at too low an rpm would have the engine 'lugging' but trying 'it' out this afternoon had me in 4th when I normally would have been in 3rd and 5th when I would have been in 4th. All seemed fine. And this must improve fuel economy.

[Mdxtasy]

I like to keep the engine singing around 2500 - 3000 rpm when cruising.  The gearing on the 318 often puts me a tad over 3k anyway....3500 is where the fun sets in so I keep it close to there.

[ovr50]

Boxgrover - your fuel economy should increase and your fun should decrease in about the same ratio....  

When I drive stick, I never shift below 3000rpms.

[tpl]

I disagree with a lot of the above...as stated...not necessarily as meant.

It depends on the torque curve of the engine involved.
Example:  My 330 is not a particulary happy engine under 2000 rpm  my previous  Audi A4 1.8 with a chip had a torque curve like a diesel and in a car just as heavy as the 330 would happily drive at 1700 rpm in 5th up hills and even accelerate.

I have driven many small ( 1.4 to 1.9 litres) diesels in Europe... given I was rarely in a hurry... upshift at 1600 rpm and let the torque do the work.  

Now I do agree that wide open throttle in a high gear always seems as if the engine is "lugging" and if the engine cannot produce enough torque at that rpm to accelerate itself under load then a lower gear is required.  Note that a normal 4 stroke Otto cycle engine is at its most efficient at WOT as there are less pumping losses.

As for low rpm fuel economy:
A colloeague of mine has a brand new C6 Corvette all 6 litres of it with an automatic.  On a given trip: Toronto to Guelph, at the same speed he gets better economy than the 330. The two cars weigh about the same, I have a bit more frontal area but not much, windows closed and a/c on in both...but he only is doing 2000 rpm and I am doing 3500.

[tigercat]

It seems counter-intuitive to many that accelerating hard from low RPMs (5th gear) can be more harmful than doing it at higher RPMs (e.g., 4th gear): They hear the engine revving higher / louder and assume the engine is working much harder.

[Minou]

Yo Boxgrover,

My Corolla has the same engine, transmission and gearing than your Vibe. I too have been driving  5 speeds for 20-25 years.

Here is an outlook of my drive last night coming back from my mother's house. On the slow 2 lane boulevard longing the St-Lawrence, I get the car in 4th, even at a slow but steady 50-65 km/hr. I don't consider that lugging because no effort is required, just cruising at 1600 rpm. Next comes the typical montreal on ramp (too short, narrow, twisty and cars coming and going from all sides). In addition, an uphill one and starting from a red light. I accelerate through 2nd and 3rd up to 4000 rpm. But right after the on ramp, I merge to the left lane and get on another on ramp, but downhill, curves to the left and traffic ahead. I shift in to 5th and just go down at 80 km/hr at 2000 rpm.  No effort asked on the engine and I slowly gather speed in the 90-100 km/hr after that. Again this is no lugging of the engine, despite the low rpm and high gear.

Basically, I do like an OD automatic transmission would, and I've been driving those often too and  observing their shift points relative to load and demand on the engine.

For normal acceleration, I generally upshift at 2800-3200 rpm, but will just get the next higher gear for any light effort constant speed cruising.

[eddie1234]

1,800 rpm is way to slow to climb a slope.
it's better to downshift to 4th gear to get a 2,500-3,000rpm range. And on most cars, 5th gear is for highway use; It is not designed to climb.

[tigercat]

Saw something on one of the French automobile shows. Only caught the tail end, but a mechanic was talking about how lugging an engine can result in inadequate lubrication in the upper cylinder walls (my French is OK, but I still may have misunderstood). True?

[Snowman]

Life with a turbo is much different. I achieve maximum boost (19 psi) at 3500 rpm. I tend to cruse on the highway around +/-3000 rpm just under 120 kph . To pass I go from 5th to 3rd and stomp, the rpm jumps to around  +/-5000 rpm (the sweeeeet zone). Under heavy spirited acceleration I shift at 6500 as not to drop below 5000.

In town I tend to drive in third at just above 3000 rpm in third, just around 75 kph in a 60. In residential zone I rarely go over 60 in a 50 zone to many things can go wrong with pedestrians and inattentive drivers in and out of driveways. I stay in third and drop down into the 2500 rpm range. When I approach any potential hazard I drop to 2nd and putt along.

I never lug an engine, what would be the purpose?

[safristi]

Aw Snowie yer just a Big PERFECT LUG...'er TIMBER...keepin' it on the cusp of or on boost ALL THE TIME must get weary and yer right foot tired..not to mention noisy,buzzy,wearing on eardrums and car parts and lots of strange looks from folks sayin" whose dat teenage noisy arse PUNK"...NO ..not the case....neighbours all DEAF!!!!

[wing]

If your driving a Honda you have no torque and must run the car at, at least 3000 rpm at all times

[mark]

James - true, but there's a difference when you have an 8000+ rpm redline, vs. a 6000 rpm redline.

[barrie1]

It always makes me wonder when I see these new Tuner cars with a 10,000 RPM Tach in them. I wonder what real purpose do they serve. I run a 8000 RPM Tach in my toy and even its more then I need with the existing cam.