[sujaylahiri]

I don't think lugging affects modern day engines anymore.
If you have a wide open throttle at a low rpm, the engine computers these days are smart enough to decrease the amount of fuel injected into the intake port (or the cylinder in case of GDI) so that there is no incomplete combustion in the cylinder.

And the engines themselves are quite sturdy these days to withstand the adverse effects (if any) of lugging.

Here's a good article by Csaba Csere of Car and Driver.
Two Ways to Improve Your Mileage: Lug and Coast - Column/Csaba Csere - The Steering Column/C/D Staff/Columns/Features/Car and Driver - Car And Driver

[anupmathur]

Originally Posted by vivekiny2k

actually lower the rpm, higher the mileage is correct factually, as long as it's done in tolerable limits.

Vivek, could you elaborate a little on how those limits might be determined?

[vivekiny2k]

Originally Posted by anupmathur

Vivek, could you elaborate a little on how those limits might be determined?

I kept that disclaimer to keep out insanely extreme behaviour .

like lowering the RPM to such an extent that car stalls or gives uncomfortable jerks.

I have lugged (if that's the correct term) my bike engine a lot and only adverse effect I got was highly undercharged battery and hence weak electricals. I used to get 70+ kmpl on my LML adreno and 50 on my father's bajaj super, while he used to get 35-40.

[bblost]

I lug my bike a lot.
Ride it like its an auto transmission.

Don't do that on my car though.

The good thing about lugging is I never have to change gears. Take anything and everything on my 5th. However the chain gets loose if you do it often.

[anupmathur]

Originally Posted by vivekiny2k

I have lugged (if that's the correct term) my bike engine a lot and only adverse effect I got was highly undercharged battery and hence weak electricals. I used to get 70+ kmpl on my LML adreno and 50 on my father's bajaj super, while he used to get 35-40.

Quite so.

The 'fuel efficiency vs bhp' graph for an engine is a 'bowl shaped' curve.
It is only towards the middle-of-the-bowl region that an engine works with maximum fuel efficiency.

[getsurya]

I never indulged in 'lugging' as felt that it does not give good power and hate the knocking sound stress coming from engine.

[Hashim]

When I drive in my university area where roads are wider and not much traffic, I always shift to 5th gear when speed reaches around 45. Then I just keep a light foot on accelarator and car crusies without any jerk. Hope this does not come under lugging.

[supremeBaleno]

Agree that driving a car in such a way that the engine feels/sounds laboured is not a good thing. But I don't think we can have universal rpms to define this which will apply the same to all cars. It would differ from car to car and you don't even need a tacho to know it. Just listen to the engine and one would know whether it is labouring or not in that particular gear at that speed.

Originally Posted by Atlblkz06

For the average gasoline engine, anything below 1750rpm in 3rd or higher hears is lugging.

As said earlier, you can't have a blanket rpm range that applies to all cars. For eg. the Baleno has really tall gearing and you can putter around in the city in 5th at 35kmph without engine complaining. The rpm in such cases is 1K or less IIRC, but that does not automatically translate to lugging.

Infact the car can go as low as 25kmph in 5th without engine complaining, but then accelerating suddenly from that speed is tough, which could imply lugging.

The main advantage I see is "not having to change gears" - it is like driving an automatic. Plus ofcourse increased fuel efficiency. I started doing this some 2 months ago when it dawned on me that inspite of racing through the gears and overtaking all and sundry, at the traffic light I invariably find myself next to the lady on Scooty who was puttering around at 25kmph.

And I am seeing impressive results from the car as far as FE is concerned. A regular 40litre fuel-up would usually take me 480kms in city before again fuelling up, but the last fuel-up needed to be done only at 570kms. I am enjoying it.

[Atlblkz06]

Originally Posted by sujaylahiri

I don't think lugging affects modern day engines anymore.
If you have a wide open throttle at a low rpm, the engine computers these days are smart enough to decrease the amount of fuel injected into the intake port (or the cylinder in case of GDI) so that there is no incomplete combustion in the cylinder.

And the engines themselves are quite sturdy these days to withstand the adverse effects (if any) of lugging.

Here's a good article by Csaba Csere of Car and Driver.
Two Ways to Improve Your Mileage: Lug and Coast - Column/Csaba Csere - The Steering Column/C/D Staff/Columns/Features/Car and Driver - Car And Driver

This may sound insane, but I disagree with Csaba on this one. Trust me, I know who he is and you would be correct to point out that his level of expertise FAR exceeds mine.

However I own the car that he "had for a weekend" and I've had plenty of time to mess with it. The car weighs 1500Kg. with me in it, has 505HP and 470ft/lb torque.

I believe that an engine's efficiency drops below a certain threshold and driving below this threshold is what I define as lugging. At anything < 900 RPM, my engine will clearly struggle and there is significant gear rollover noise as well in 3rd and higher gears despite having 300 ft/lb of torque!. Csaba wants to run it at 800 RPM...

When you step on the gas at 1000rpm in 6th gear - mileage plummets from 45 to 15mpg and yet you get hardly any acceleration. So where is the fuel going? In 5th gear you would get about 3x the acceleration and only drop down to 13mpg or so. CLEARLY 6th gear is a poor choice. By downshifting to 5th, your mileage is actually improving since you would have to spend 3 times the amount of time at 15 mpg instead of accelerating at 13 for 1/3rd the time and maintaining speed at 30mpg+ for the other 2/3rds.

Lugging may not "damage" the engine as you pointed out - but I believe you are LOSING fuel economy AND acceleration by driving at ultra low RPMS. Its simply a lose-lose situation and you may also be pissing off others behind you by accelerating like a hyper miler.

As someone pointed out on the first page - its definitely possible to lug even in 3th gear at 3000rpm. In this case the engine RPMs will drop and you will need to downshift to second and go up that hill at 4500rpm!

Every case is different, so my example probably will not apply to you.

About redliing - my motor sees 6000RPM pretty much every time it's driven (redline at 7k). I dont believe in babying the motor. I'm looking forward to adding an Integra GSR or some car that I can revv the piss out of for fun. Doing that in the vette will land me in jail pretty quickly lol.

Anyway.. I have a job interview in the morning so I better get to bed.

Originally Posted by supremeBaleno

But I don't think we can have universal rpms to define this which will apply the same to all cars. It would differ from car to car and you don't even need a tacho to know it.

I agree with you 100%. My original post was typed in a bit of a rush since I had to board the plane. I threw some numbers out there just for reference, but my wording is misleading. Haste makes waste...

[vivekiny2k]

Originally Posted by anupmathur

Quite so.

The 'fuel efficiency vs bhp' graph for an engine is a 'bowl shaped' curve.
It is only towards the middle-of-the-bowl region that an engine works with maximum fuel efficiency.

ok, this is just a comment for fun, but:

did you notice there is no RPM in your statement

[condor]

Atlblkz06 : There is no clear definition for this since the parameters are different for all cars.

When in gear, if you accelerate and the car is unable to accelerate - that is lugging.

If you hear gurgling, grinding or other noises that reduce when the RPMS increase - thats lugging

It's not as much about not having a clear definition, as it is about having a slightly long-drawn, vehicle specific explaination of lugging. But the easiest way to know if you are lugging is when you hear that gurgling, grinding noise - with the engine at low RPM's, struggling to keep pace / accelerate.

As you can guess, I never do.

Keep the vehicle in the power-band. Have sufficient power at all times. A engine that's kept within it's power-band may return a slightly less FE, but it remains healthy much longer.

phamilyman : On the contrary, lugging is perfectly fine for diesels.

Why so ?

With turbo diesels, it just does not make sense to lug ! Get the revs sufficiently high to feed in that little more air to ensure a full burn of the fuel.

One may argue that the engine management system will supply lesser fuel, but that lesser fuel will mean more time to come up to desired speed.

rippergeo : I wonder if I lug my engine. ..

and the car picks up faster than most other vehicles on the road when the accelerator is depressed from that rpm.

helps if you can specify which car.

May be these others around you lug more than you ?

[Shan2nu]

Driving for FE is not that easy.

Its a fine balance between engine speed and vehicle speed.

For eg :
If a car does 100kmph@2700rpm in 5th, while consuming 4.3ltrs a hr the FE at a constant speed would be around 23kmpl.

And if this same car does 80kmph@2200rpm in 5th, consuming 3.6ltrs an hr, its FE would be 22kmpl.

In this case, you're not only reaching your destination faster but also getting more out of each liter of fuel.

So, instead of letting you engine revv as low as possible, do a few tests and see what combination of engine and vehicle speed works out best for your car.

Shan2nu

Originally Posted by condor

helps if you can specify which car.

May be these others around you lug more than you ?

Pete'd swift.
yes, I did think of that explanation, but you cant mistake a bike motor being revved in order to squeeze past into the gap in front of you. It is such a lot of fun shutting the door on an over revving petrol :-)

I'm still worried that I'm lugging inspite of the decent performance i get at the lower revs, and I'm willing to change my driving style. but the engine seems very happy accelerating from idle in 3rd at 20kmph. should i change my driving style? I get 16.5 in city traffic with the AC on all the time.
I rev away to glory on the highways.

[anupmathur]

Originally Posted by vivekiny2k

ok, this is just a comment for fun, but:

did you notice there is no RPM in your statement

You're so right!
That's because most performance and FE related issues are more bhp based than rpm based, thanks to the gearbox!
The real life issue is that there is no easy way for a user to gauge what bhp is being developed at any given moment!

[watashi75]

Contrary to popular belief, lugging may not always give best fuel efficiency. Let us assume for simplicity that fuel consumed is approximately RPM times throttle width.

First example, for a car lugging uphill in 3rd gear at 1500 RPM at full throttle,

Amount of fuel consumed = 1500 * 1 = 1500 units

If it is possible to do the same in 2nd gear at 2250 RPM (Swift gear ratio) at half throttle,

Amount of fuel consumed = 2250 * 0.5 = 1125 units

Second example, if a car is moving in 5th gear at 3000 RPM at full throttle

Amount of fuel consumed = 3000 * 1 = 3000 units

If it is possible to maintain this speed in 4th gear at 3850 RPM with even 3/4 throttle,

Amount of fuel consumed = 3850 * 0.75 = 2887.5 units