[anupmathur]

Originally Posted by supremeBaleno

You do have a point. But again I would think that this depends on the engine capability. If your car engine produces enough torque at really low rpms that enable the car to climb up gradients without straining the engine, I would think it OK. But if you try the same thing on another lower-specced car, it might strain the engine, in which case, its would be a no-no.

Quite right but still the engine would not be at the desired/ideal operating point. At the very least it would be an inefficient operation.

[architect]

OK, then here's how I understand it:

1. Chugging along on 1st & 2nd gear at idling RPM is fine as it doesn't seem to lug. So it means both Rippergeo and me are doing fine on our Multijet / DDIS in crawling traffic.

2. Picking up from idling, one might have to downshift. However, I think, practically, that on 2nd gear one does not need it. On idling in 3rd gear, one has to downshift to 2nd and then upshift to 3rd again. This I am saying in terms of difficulty in accelaration. On the torquier Safari, Suman seems to comfortable pull in 4th from idle to mid-range.

3. I park my car at a bottom of a slope and I often start off (after idling for 45-60 seconds, of course) by simply releasing the clutch and the car takes me comfortably up the slope without A-pedal. While it is not a very gentle slope, it is not as steep as a parking ramp either. The ECU seems to do it fine by increasing fuel supply (and consequently, RPM) to the engine, it may not be a great idea for the engine. In a way it is lugging (but mitigated by ECU and the bottom end torque of the engine.) So, allowing ECU to manipulate RPM up the inclines while not pressing A-pedal is not advisable.

@Anupmathur and SamirTaheer: Both of you suggest that moving at idling RPM is inefficient. But isn't it more efficient than moving along at half clutch? I mean which of the two would you prefer, if you drove a car with a heavy clutch like mine:

(a) Moving constantly at 700 RPM on 2nd gear or

(b) De-clutching / braking / accelerating / braking / de-clutching on 1st gear to maintain constant 1500 RPM and constant gap between yourself and the guy in front of you.

I would prefer (a) moving at a constant 700 RPM on 2nd gear as long as my car doesn't seem to be lugging. Agreed that it is not the best situation, but isn't it better than situation (b)? Or do I HAVE to make a choice between engine life and health on one hand and clutch life and calf-muscle health on the other?

I would point out that the RPM increases when I start moving up an incline, from what I remember, but I shall check carefully whether it always does so when I start at a level ground.

[teknophobia]

Originally Posted by anupmathur

Tekno, please take a look at this: Diesel engine combustion efficiency
and: Knocking detection device in diesel engine - Patent 4567751

And: Automotive: knocking in diesel engine, vw golf diesel, vw dealer

Did you read these before posting?

To quote from your first article:

In a spark ignited engine, it is best if the spark control the ignition,since timing of the piston motion with the motion of the flame front is critical to the operation of an efficient engine. In a diesel engine, one relies on auto ignition of the fuel because the engine is basically compression ignited (there is no spark plug). Therefore, we want the fuel to be autoignited.

In reference to your second link, I never stated that diesel engines don't knock, I merely stated that knock as you know it in a petrol engine is completely different from that in a diesel engine. In a petrol engine knock occurs when auto - ignition occurs, in diesels knock occurs when the timing of the injectors is off and the fuel is injected before it is supposed to be.

And I fail to understand how the third link has any relevance at all.

My post was merely in response to your post equating octane and cetane numbers. In any case this is going completely off topic.

[anupmathur]

Originally Posted by architect

(a) Moving constantly at 700 RPM on 2nd gear or

(b) De-clutching / braking / accelerating / braking / de-clutching on 1st gear to maintain constant 1500 RPM and constant gap between yourself and the guy in front of you.

Option (a) without a doubt!

Further, IMO, occasional lugging does not do grievous harm to an engine, nor does it materially reduce engine longevity.
These discussions are more academic than of vital practical use!
However, I do believe that an engine should lead a well rounded life with a healthy mix of a bit of lugging, a bit of moderate usage and a bit of redlining!

[SS-Traveller]

Originally Posted by architect

OK, then here's how I understand it:

1. Chugging along on 1st & 2nd gear at idling RPM is fine as it doesn't seem to lug.

Originally Posted by anupmathur

IMO, occasional lugging does not do grievous harm to an engine, nor does it materially reduce engine longevity.

IMHO, if, while lugging the engine, one does cause a driveline shunt inadvertently, that would cause grievous harm as well as materially reduce clutch and other transmission component life. And not all drivers are expert at totally avoiding driveline shunting while driving in high gear at low RPM. So, shouldn't attempts to lug the engine by a new driver be avoided in the fear that a driveline shunting can suddenly be set off?

[anupmathur]

Originally Posted by SS-Traveller

So, shouldn't attempts to lug the engine by a new driver be avoided in the fear that a driveline shunting can suddenly be set off?

Quite right, but that is an extreme case. Yet, it is so common amongst many drivers. Do their car transmissions go bust? Very stressful for the mechanicals, no doubt, but they seem to survive well enough!
Not at all recommending anything like this, LOL!
And if such things happen while I am also in the car, they prove very stressful for me as well!

[SS-Traveller]

Originally Posted by anupmathur

Do their car transmissions go bust?

I would think so. Synchromesh lock failure (resulting in gears jumping out into neutral) and differential gear damage (resulting in diff whine), apart from shortened clutch life, is usually because of repeated driveline shunting.

[Samir Taheer]

SS_Traveller - Very valid case. There have been cases (none i have seen or experienced personally), where due to the driver being in too high a gear and trying to pick up pace, the driveshaft breaks.( I think its the driveshaft).

As for Architects options id go with A too, but i dont deny i dont use option B too.

[anupmathur]

Originally Posted by Samir Taheer

There have been cases (none i have seen or experienced personally), .....

That's the point I was trying to make.
In decades of seeing BAD drivers, I haven't personally come across ONE such incident!

[SS-Traveller]

Originally Posted by Samir Taheer

SS_Traveller - Very valid case. There have been cases (none i have seen or experienced personally), where due to the driver being in too high a gear and trying to pick up pace, the driveshaft breaks.

In my years spent in garages, I've seen too many synchromeshes, gear teeth, clutches, U-joints and CV-joints damaged prematurely, supposedly due to driveline shunt, for it not to be funny. Now, a direct cause-effect relationship can only be deduced and not pin-pointed for the same, but the only culprit that causes such damage is driveline shunting. I've seen less of this kind of damage in Delhi than in Kolkata (which is also to say I've spent far less time in garages in Delhi than in Kolkata), and my reasoning is that people do tend to lug engines more in the slow-speed traffic of Kolkata to eke out maximum mileage, and Delhi traffic is (was?) faster and smoother, allowing higher speeds and less chances of shunting.

[anupmathur]

The Demographic Profile of Engine Luggers!
Might even become a best seller!

[janitha]

Somebody pl explain "driveline shunting".

[architect]

Originally Posted by Samir Taheer

SS_Traveller - Very valid case. There have been cases (none i have seen or experienced personally), where due to the driver being in too high a gear and trying to pick up pace, the driveshaft breaks.( I think its the driveshaft).

Does driveshaft breakage mean only driveshaft breakage or does it also include gearbox components?

My father broke the rear axle of his Amabassador in his younger days by trying to lug in first gear. I guess this is similar, right?

Originally Posted by Samir Taheer

As for Architects options id go with A too, but i dont deny i dont use option B too.

Actually, I start with option B and then when I realise that the situation is going to last longer, I move to option A.

[SS-Traveller]

Originally Posted by anupmathur

The Demographic Profile of Engine Luggers!
Might even become a best seller!

Only if you are co-authoring it, Mathur-saab!

Originally Posted by architect

Does driveshaft breakage mean only driveshaft breakage or does it also include gearbox components?

My father broke the rear axle of his Amabassador in his younger days by trying to lug in first gear. I guess this is similar, right?

Yes, something similar. The driveshaft is to the front drive car (with a constant velocity or CV joint incorporated into it), what the axle is to reardrives with a full floating diff (like in the Amby, Fiat and Mahindras) - with independent rear suspension in rear drive cars, it is again called a drive shaft. Driveshaft damage is usually seen at the CV joint (resulting in the krrr krrr sound when driving on full steering lock). The Amby axle, of course, was notorious for breaking when trying to do wheelspins in 1st gear!

[archat68]

Originally Posted by janitha

Somebody pl explain "driveline shunting".

Please explain driveline shunting.