[Nalin1]

Originally Posted by Jeroen

I refer to my earlier post: This is only a concern for people who frequent car forum. The rest of the world, say 99% of car owners would not even know what you are talking about, nor care. In fact, many car owners would not even know if they were driving a car with or without a turbo engine, nor could they care.

This is something that we always need to keep in mind before getting emotional and getting carried away. Car manufacturers have to look at the big picture and the actual mindset of buyers, when making decisions. Not looking to hurt the sentiments of enthusiasts is secondary for them.

But that need not have any impact on the discussions here. We are free to rip apart cars .

[jagdish_ker]

Take the case of a car driven in countries which follow traffic system as listed below
1. There aren’t any traffic signals in highways (100, 120kmph or no speed limit and no casual stopping)
2. Where speed limit is reduced to 50, 60 or 80kmph once you exit a highway
3. Traffic signals are usually found only in </= 50kmph zone
4. Your final destination will be either in a 50 or a 30kmph zone

In this case, by the time you see a red light or need to stop at a destination, your engine would have been running at a just above idle speed for a while. So German cars will not face any issues with these in their homeland.
Anywhere else, I would idle a turbo engine for at least for half a minute (few seconds for any NA engine) before I turn it off. No matter where, I switch off start-stop first thing I start driving (trying hard to remember this every time) as my drives mostly are less than 10km when engine temperature gauge doesn’t usually reach mid mark. From a user perspective, I strongly believe companies should provide means to switch this feature off permanently. Let the driver take decision and turn off the engine if the halt is more than a minute or so. I am not comfortable restarting a cold engine unnecessarily (even if the car’s AI feels it is alright. I believe it is an unnecessary reason causing more wear and tear). I believe start-stop feature is a nuisance in cities like Chennai or Bangalore.

[gopa99]

Originally Posted by shancz

Jeroen's post is apt.

Attachment 2111189

Recommends a few seconds of idling before shutdown.

Attachment 2111191
The ESS considers a variety of parameters before stopping the engine so like mentioned it should be smart enough.

Attachment 2111218

Thanks

This is a nice quote from the manufacturer to explain the point, I felt the key point mentioned in the owners manual is that the "Engine will stop after a specific time period". IMO the important thing for the turbo idling theory is to allow the lubricant to flow and not get hot trapped inside the hot turbo bearings and lead to consequent damage.

[bullrun87]

I have to maintain a strict speed limit of 25 kmph at my workplace. This means driving at 25kmph every day for a few kms. Driving at such slow speeds is really boring so I have developed a habit of simply driving my figo TDCI in third gear without using the accelerator at all. Driving in second at 20-25kmph is also noisier and one needs to constantly press the accelerator. My car runs at 21-22 kmph at about 800-900 rpm in third. This way as I don't accelerate, I will never even accidentally cross 25kmph. Will driving at idle speeds for several kilometers a day have any undesirable effect such as lugging the turbo?

[apachelongbow]

Turbo doesn't work at idle rpm. Your worry is unfounded. The wastegate powering the turbo opens typically at around 1300/1500 rpm in most engines where as idling rpm is between 800/900 rpm.

[Jeroen]

Originally Posted by bullrun87

I have to maintain a strict speed limit of 25 kmph at my workplace. This means driving at 25kmph every day for a few kms. Driving at such slow speeds is really boring so I have developed a habit of simply driving my figo TDCI in third gear without using the accelerator at all. Driving in second at 20-25kmph is also noisier and one needs to constantly press the accelerator. My car runs at 21-22 kmph at about 800-900 rpm in third. This way as I don't accelerate, I will never even accidentally cross 25kmph. Will driving at idle speeds for several kilometers a day have any undesirable effect such as lugging the turbo?

Originally Posted by apachelongbow

Turbo doesn't work at idle rpm. Your worry is unfounded. The wastegate powering the turbo opens typically at around 1300/1500 rpm in most engines where as idling rpm is between 800/900 rpm.

Contrary to popular belief your turbo always spins.

Also at idle engine RPM.

The waste gaste does not power the turbo. Essentially a wastegaste is a safety device (valve) ensuring the boost pressure does not rise to high. It divert excess exhaust gases away from the turbo – controlling the speed of the turbo and preventing it from spinning too fast, thus controlling the boost pressure. It is not the engine RPM that controls the waste gate. It is the boost pressure, which is a function of engine loading.

So running your car in third gear, at idle RPM, is nothing unusual for the turbo. It will still spin a bit. Although you are idling the engine, it is producing some power. So the exhaust gases will be a little higher than when your engine just runs idle, with the car standing still. So the turbo will run a bit faster as well.

So nothing unusual for the turbo, none whatsoever.

Whether driving in such a manner constitutes good practice remains to be seen though. In general, as long as you are not lugging the engine, in theory you should be good. However, you are operating at the edge of the envelop so to speak. Which is usually far from optimum. My rule of thumb is that if you press the accelerator the car should still be able to accelerate reasonable. If it does not, you are in too high a gear. (i.e. if it starts lugging when you press the accelerator you’re definitely in the wrong gear)

Your engine is under a somewhat higher load, than at standstill idle. But your oil pump is running at idle speed as well. But the higher engine load means that the pistons push harder into the bearing, as when they do when idling at standstill. But the amount of oil being circulated and the pressure at which it is delivered is a bit lower.

Not sure if it would be very fuel efficient either, which in itself tends to lead to slightly more emission, soot etc.

There are some theories around how dual mass flywheels don’t like low revs with higher engine loads.

Same around the gearbox/transmission; you are putting a relative high(er) torque through the number three gear at an unusual low RPM. Would that affect the lubrication?

It is all a bit theoretical and I cant put a number on it.

I have noticed that a lot of our members seem somewhat reluctant to rev their engines, under the unassumption it introduces wear. The opposite is actually true. Engines and gearboxes do best (from a wear and tear point of view) at decent RPMs and loading of at least 50-60%.

But as I mentioned earlier; no problems for your turbo, everything else is a bit theoretical.

Jeroen

[Artyom]

Slightly Off Topic but I wanted to check if the same rule of idling the engine (Cold Start) with a NA engine is also recommended or necessary to be specific.
On a cold start, I keep the engine idle for a minute and then I drive off. I have a Creta Petrol 1.6 .Kindly suggets.

[Jeroen]

Originally Posted by Artyom

Slightly Off Topic but I wanted to check if the same rule of idling the engine (Cold Start) with a NA engine is also recommended or necessary to be specific.
On a cold start, I keep the engine idle for a minute and then I drive off. I have a Creta Petrol 1.6 .Kindly suggets.

Check the owner manual. My guess is it will tell you not to idle, certainly not for a minute, but drive off straight away gently. Keep the rpm and engine loading low until the engine has reached normal operating temperature.

When you start your engine, the oil pump kicks in immediately and you will have proper lubrication everywhere within seconds including a turbo.

Leaving an engine trifling for a minute will do nothing other than pollute and extra wear and tear. Piston/ cylinder lubrication is very poor at low temperatures. Modern engines, especially diesel, will simply not warm up at idle. You need to load them up a bit, which means drive away!

Jeroen

[White Aviator]

I'm a believer of idling the engines. None of my vehicles are turbocharged, yet I idle all my vehicles, scooter, bike and car for atleast a minute before leaving and for 30 seconds to a minute after coming to a stop. I think it gets all the juices flowing and the oil, coolant, etc are at all the places they need to be.
They are just like us humans. We wouldn't want to start running right away after getting out of the bed, nor would we want to get into bed right after a run.

For these newer turbocharged engines, I think the manufacturers must have taken into account that most people would not bother to idle them, as pointed out by many BHPians. Even the showroom staff do not inform about this while delivering the cars. The word of mouth recommendation works wonders and manufacturers wouldn't want their car to be named as unreliable. Hence, I think there is no reason to worry even if the start/stop system is active.
Notice the user manual photos mention it is necessary to idle after 'hard driving'. For those like us who care very much about our vehicles, it would be best to turn off the auto start/stop system while going on the highway. In city its ok to be left on as there is no 'hard driving' involved and it would also save some precious fuel. The average user wouldn't bother about it and it wouldn't be an issue I believe. In the long run, there will be some effects but people who take care of their car in general always end up with a better running vehicle having lower maintenance costs. Those cautious like us can surely remember to turn off the system while on the highway or while approaching a toll booth.

[Jeroen]

Originally Posted by White Aviator

I'm a believer of idling the engines. None of my vehicles are turbocharged, yet I idle all my vehicles, scooter, bike and car for atleast a minute before leaving and for 30 seconds to a minute after coming to a stop. I think it gets all the juices flowing and the oil, coolant, etc are at all the places they need to be.
They are just like us humans. We wouldn't want to start running right away after getting out of the bed, nor would we want to get into bed right after a run.
.

No, they are not like humans. But unlike humans they do come with an owner manual and you should follow whatever it says it the manual.

As I pointed out earlier, idling an engine for a minute is just not a good idea. I know you think you are looking after your engine, but you are not. When you start an engine, within seconds it will have oil pressure and oil everywhere.

When it comes to coolant, well the same is true, but there is nothing to cool, because the engine is stone cold, so also the thermostat is fully closed, meaning your pump is just pumping water round and round the radiator, not through you engine at all!

The biggest problem is that cold lub oil does not adhere very well to cold cilinder walls. So this causes wear. A minute idling does not increase the temperature of your lub oil at all. You are just grinding the piston rings along the cilinder surface with poor lubrication. So that is why you need to start and drive off without undue idling. Keep the RPMs low, don’t load the engine until it is properly warmed up.

There is a reason why cars that are used for lots of short drives often use a lot of oil. They never reach normal operating temperature. That causes a lot of wear and tear.

Short duration trips and long idling of a cold engine are the worst for wear and tear of your engine. Don’t trust me, or the internet, read your owner manual.

Jeroen

[Dr.AD]

Originally Posted by Jeroen

Check the owner manual. My guess is it will tell you not to idle, certainly not for a minute, but drive off straight away gently. Keep the rpm and engine loading low until the engine has reached normal operating temperature.
Jeroen

Thank you Jeroen for clearing this very common myth. Idling on cold start is actually the worst thing you can do on a cold start :-)

After Jeroen reminded us of this, I double checked the manual of my BMW 320d, and it indeed confirms what he said. Here is what my manual says about cold start:

Originally Posted by Dr.AD

In most cases, these auto engine off systems are smart enough to know when it is safe to switch off the engine and when it is not. The algorithm used to decide when to switch off the engine does not work blindly every time you come to a stop. The system monitors several parameters including various temperatures, engine runtime since the start, and even the AC settings. The system algorithm considers all these parameters and switches off the engine when it is safe to do.

I double checked my manual for this too, and here is an elaborate list of checks that the manual mentions before the auto-off system switches off the engine:



So again, it is not a dumb system that will casually switch off the engine at every single stop. It is a pretty sophisticated system that knows what it is doing.

I still do not like it because it simply annoys me, and I keep it disabled for that reason. But there is no danger in using this system if one likes it.

P.S. And BTW, my manual nowhere mentions any idling requirements at all. So regardless of whether the auto on/off system is used or not, there is no separate mention of any idling requirements even after hard driving. And this while it does mention a few other precautionary "hints" under "driving hints", but none related to idling (unless I missed it in my search).

[a4_attitude]

I drive Porsche Macan 2020 and am new to start stop function, some times I think its not calculating the right algorithm where it stops the engine in bumper to bumper traffic which is annoying
Little off topic to subject, Do you guys think start stop function actually consumes more fuel, as every time you start the engine, it tend to inject extra fuel for engine, so every time with a few seconds of difference we are consuming more fuel?

[Dr.AD]

Originally Posted by a4_attitude

Little off topic to subject, Do you guys think start stop function actually consumes more fuel, as every time you start the engine, it tend to inject extra fuel for engine, so every time with a few seconds of difference we are consuming more fuel?

No, that is not true. It was back in the carburetor days that restarting engine consumed more fuel. Modern cars do not consume more fuel for restarting the engine. Purely from fuel saving point of view, start-stop system does indeed save a small amount of fuel (it may be too tiny to make any big difference depending on one's driving conditions, but it does save some non-zero amount of fuel).

However, this system can still be annoying as you mentioned, and I keep it disabled for that reason. But purely technically speaking, this system does no harm, either for the longevity of the engine or for fuel consumption.

[White Aviator]

Originally Posted by Jeroen

No, they are not like humans. But unlike humans they do come with an owner manual and you should follow whatever it says it the manual.

As I pointed out earlier, idling an engine for a minute is just not a good idea. I know you think you are looking after your engine, but you are not. When you start an engine, within seconds it will have oil pressure and oil everywhere.

When it comes to coolant, well the same is true, but there is nothing to cool, because the engine is stone cold, so also the thermostat is fully closed, meaning your pump is just pumping water round and round the radiator, not through you engine at all!

The biggest problem is that cold lub oil does not adhere very well to cold cilinder walls. So this causes wear. A minute idling does not increase the temperature of your lub oil at all. You are just grinding the piston rings along the cilinder surface with poor lubrication. So that is why you need to start and drive off without undue idling. Keep the RPMs low, don’t load the engine until it is properly warmed up.

Jeroen

Makes sense what you say.
For me, this idling routine began 4 years back when I purchased my Duke 250. After a cold start when I pull in the clutch, I hear some weird knocking sound from the engine/clutch (I'm not sure which). There is no such sound when the bike is warm.

I had raised this query during my first service and had this checked, fortunately everything was normal and they told me it was just because the bike is cold.
After this I started idling my bike for a minute, the temp guage shows one or two bars and then I leave. There was no more of that knocking sound so I was happy and started doing it with every other vehicle.

I do get your point though so I will proceed to check the user manuals if something related to this is mentioned.

[venkyhere]

Originally Posted by Jeroen

Short duration trips and long idling of a cold engine are the worst for wear and tear of your engine. Don’t trust me, or the internet, read your owner manual.

Jeroen

what if there is a steep ramp to climb out of parking, on a cold morning ? what will be your take on what to do in that case ?
1) start moving from parked position in 10 seconds and then when engine temp is low, climb the ramp & load the engine
OR
2) idle for 1 min, move out of parked position and climb the ramp & load the engine when engine is slightly warmer