[s_pphilip]

Originally Posted by Jeroen

On 1: More advanced ECU's will disable the AC during the start cycle and only switch on once the engine idles. Once it idles the AC does put a bit of extra load on the engine, but nothing much. Your typical AC on a midsize saloon would probably pull the equivalent off 6-8 HP. Not much to get exited about for you or the turbo. Typically all AC's are automatically disabled below approx 4oC anyway.

Coolant temperature is not the best way to really judge what is happening temperature wise. It's the oil temperature which is relevant for your engine and turbo. And that temperature could lack behind the coolant temperature. Especially with engines with large volumes of oil. Better indication can be, if you have one the oil pressure indicator. Only when the engine oil reaches its normal operating temperature will that start showing normal readings too.

On 2: No worries, you can switch on and off as often as you like. Other than wearing out the on/off switch and possible the AC clutch you have nothing to worry about this engine wise. Accelerating away from a traffic light puts a considerable higher load on the engine, than switching your AC on.

On 3: If you want to keep cool, keep the engine and AC running at all times.
If you want to save fuel and the environment, switch the engine off.
There is nothing else to it.

On 4: Don't worry these things happen all the time. If you do it a couple of thousand times maybe you should worry.

In general and I think I said this before; There are a couple of dozen guys on this forum who worry about the idling rule for Turbo's. There are literally tens of millions other guys out there who never even heard about the rule and are pottering around with their turbo's never getting idled. At least not on purpose.

Reading through this thread you'd think the world would be awash with damaged turbo's. The fact is that a failed turbo due to not adhering to the idling rule is a very rare occurrence indeed.

So just go by what the owner manual advises and if you forget once in a while, just don't worry about it.

Enjoy your car.

Jeroen

Wow that clarifies some of my earlier expressed doubts about TC and AC.

[pahwa]

Originally Posted by GTO

Abusing your turbocharger can affect its longevity. With time, the turbo will become less effective. Take care of your turbo so that it gives your engine adequate boost and thus, an enjoyable driving experience for years to come.

Hi GTO


I got advised by someone that I should keep atleast 20L of fuel in the tank at all times to avoid fuel pump and turbo failure in diesel turbo-charged cars.

Is there any scientific explanation for this or it is just another myth?

Thanks

[ghodlur]

Recently at a refueling station when I was waiting for a minute to idle before switch off, the attendant amusing smiled at me and said that I was being too over cautious about the engine for doing so. I told him that its a diesel car and have to do that for which he replied, he hasnt seen any diesel car being idled before switch off at a petrol bunk. Everybody switches off instantly. if everyone starts idling for a minute, there will be a huge line for diesel refueling.

I sternly told him, I am not one of them.

[Arch-Angel]

Originally Posted by pahwa

I got advised by someone that I should keep atleast 20L of fuel in the tank at all times to avoid fuel pump and turbo failure in diesel turbo-charged cars.

Is there any scientific explanation for this or it is just another myth?

Thanks

This is a myth in my opinion. The reason we shouldn't let the tank go to the lowest fuel level is because we don't want any sediments which may have settled in the bottom go into the fuel lines. That aside, fuel isn't what cools the turbo. Its the oil that does the job.

[shinuak]

Originally Posted by Arch-Angel

This is a myth in my opinion. The reason we shouldn't let the tank go to the lowest fuel level is because we don't want any sediments which may have settled in the bottom go into the fuel lines. That aside, fuel isn't what cools the turbo. Its the oil that does the job.

Isn't this a myth too ? Think about a car, or for that matter any automobile which accelerates, decelerates, goes over potholes, humps etc. This will make the fuel in the fuel tank mix with all the sediments and will almost be like putting everything inside a blender. So where is the point of sediments not entering the fuel pump even if the fuel level is high. I think the sediment stuff may have an impact on the fuel filter / injector etc but that is something which cannot be a avoided whether we have a full tank or half empty tank, right ?

[debuda]

Originally Posted by pahwa

Hi GTO


I got advised by someone that I should keep atleast 20L of fuel in the tank at all times to avoid fuel pump and turbo failure in diesel turbo-charged cars.

Is there any scientific explanation for this or it is just another myth?

Thanks

One should never allow the fuel level in a CRDI diesel car to fall so low that the engine stops due to fuel starvation. This has nothing to do with the turbo however.

CRDI engines use very high pressure positive displacement fuel pumps to maintain high pressure in the common rail (manifold) which feeds fuel to all the injectors. These pumps have very fine clearances and are lubricated / cooled by the diesel flowing through them. If the fuel tank becomes empty when the car is running, this pump will run dry for a few seconds before the car stops and this may damage the pump.

Additionally, to the best of my knowledge, the electronic injectors in a CRDI engine are also cooled / lubricated by the diesel flowing through them and may suffer damage if there is fuel starvation.

Sediments creating problems when the fuel level in the tank is low is nothing but a myth. Firstly, the fuel suction pipe opening is always at the lowest point in the fuel tank where sediments, if any, will collect regardless of how full or empty the tank is. Secondly, CRDI engines have very efficient diesel filters which not only capture any particulate matter but also water or moisture.

[Jeroen]

Originally Posted by debuda

One should never allow the fuel level in a CRDI diesel car to fall so low that the engine stops due to fuel starvation. This has nothing to do with the turbo however.

CRDI engines use very high pressure positive displacement fuel pumps to maintain high pressure in the common rail (manifold) which feeds fuel to all the injectors. These pumps have very fine clearances and are lubricated / cooled by the diesel flowing through them. If the fuel tank becomes empty when the car is running, this pump will run dry for a few seconds before the car stops and this may damage the pump.

Additionally, to the best of my knowledge, the electronic injectors in a CRDI engine are also cooled / lubricated by the diesel flowing through them and may suffer damage if there is fuel starvation.

Sediments creating problems when the fuel level in the tank is low is nothing but a myth. Firstly, the fuel suction pipe opening is always at the lowest point in the fuel tank where sediments, if any, will collect regardless of how full or empty the tank is. Secondly, CRDI engines have very efficient diesel filters which not only capture any particulate matter but also water or moisture.

Absolutely, I fully agree. The main consideration is the HP fuel pump. Not sure how effective diesel filters are at capturing water though.

In fact all of the above is true for petrol engines too! Although, in practice the diesel variant is likely to suffer more/quicker than the petrol variant.

[Arch-Angel]

Originally Posted by shinuak

Isn't this a myth too ? Think about a car, or for that matter any automobile which accelerates, decelerates, goes over potholes, humps etc. This will make the fuel in the fuel tank mix with all the sediments and will almost be like putting everything inside a blender. So where is the point of sediments not entering the fuel pump even if the fuel level is high. I think the sediment stuff may have an impact on the fuel filter / injector etc but that is something which cannot be a avoided whether we have a full tank or half empty tank, right ?

This is a fact as well. But over this sediment impact, i was told that you would not want the fuel pump to run dry. So it is like fuel level in this context and i mixed both of them up .
Sediments are taken care of by the filter as you said.
P.S: Debuda has put the points i had in mind on paper. Correct reason.

[9thsphinx]

MYTH #7

You have to let a turbo-diesel idle for two minutes before you shut it off.

FACT

This is a current myth that has a basis of fact stemming from many years ago. It also has a kernel of truth regarding today's turbocharged gasoline engines that operate at higher peak exhaust temperatures than turbo-diesels. In the early days of turbochargers, the turbo shaft was supported by a babbitt bearing that could seize, or even melt, if the engine was shut off immediately after sustained boost conditions where the turbocharger would "heat soak". A two minute cool down at idle allowed the turbocharger to dissipate any remaining spinning inertia, and the oil circulation cooled the bearing and prevented oil "coking" in the bearing area. Turbochargers haven't used babbitt bearings for over 30 years, and today's oils resist coking. Synthetic oils won't coke, period. With a turbocharged gas engine, it's still good insurance to let the engine idle for 30 seconds to a minute to allow the turbo or turbos to dissipate any inertia and to cool the bearing area to prevent oil coking, especially if the engine has been worked hard just prior to shut-down. Of course, using quality synthetic oil eliminates this potential coking problem.

Today's turbo-diesels are a different story. There is really no reason to "cool down" a turbo-diesel these days, but you won't hurt anything by doing it either. You can still find people who swear you have to do it, but the myth is fading. Maybe they just like to sit and listen to the radio.

Source: Banks Power

There are so many contradictory articles all over the web that it is hard to decide on what should really be followed. As a general rule, you should idle if you've driven hard and fast, and you don't need to idle if the last few minutes of your driving has been done at low RPM's.

[Jeroen]

Originally Posted by 9thsphinx

There are so many contradictory articles all over the web that it is hard to decide on what should really be followed. As a general rule, you should idle if you've driven hard and fast, and you don't need to idle if the last few minutes of your driving has been done at low RPM's.

I'd say as a general rule you need to adhere what the manufacturer recommends in the manual before doing anything that's out on the web!

Jeroen

[puchoo]

Agree completely , in my case , the owners manual recommendation is clear and simple and something i have been doing none the less for most of my driving life - if driven hard for a decent period of time , let the engine cool down by running it for 30 odd seconds - there is no other recommendation.

I give it a minute atleast after a hard run , and about 10-15 seconds after even a very very light run ( 8-9 Kms , 30-40 Kmph max)

Originally Posted by Jeroen

I'd say as a general rule you need to adhere what the manufacturer recommends in the manual before doing anything that's out on the web!

Jeroen

[mpksuhas]

Friends diesel Polo started having issues with door locking after he switched off the car abruptly after a highway run of around two hours. As per VW service center issue is due to sensors getting, well to put the idea across "confused" on switching off without idling. The issue was not reported after that and needless to say he now idles for more than a minute.

[Jeroen]

Originally Posted by mpksuhas

Friends diesel Polo started having issues with door locking after he switched off the car abruptly after a highway run of around two hours. As per VW service center issue is due to sensors getting, well to put the idea across "confused" on switching off without idling. The issue was not reported after that and needless to say he now idles for more than a minute.

That is remarkable, I dont understand the correlation between doors not locking and not idling. Could somebody explain that in a technical way, what sensors are getting confused, what interlocking logic is in place etc? Certainly a new feature to me!


Jeroen

[shankar.balan]

Originally Posted by mpksuhas

Friends diesel Polo started having issues with door locking after he switched off the car abruptly after a highway run of around two hours. As per VW service center issue is due to sensors getting, well to put the idea across "confused" on switching off without idling. The issue was not reported after that and needless to say he now idles for more than a minute.

This is weird and rather improbable to say the least. There must be some other reason for this 'confusion'.

I have been using Turbo charged Diesel cars now since about 2008. I have religiously followed the 30-40 second idling rule before cutting off the engine.
However, for the most part, we do not tend to drive quickly since we are mostly running about the city in traffic. Despite this fact, I try and practice the idling rule as a matter of course.
On highway runs where the speeds are higher and one drives at consistently higher speeds for longer sustained periods of time, I try to be extremely careful about the idling rule. After all, it is my hard earned money that I ve spent to buy this lovely car and the least I can do is to look after it the way it deserves to be looked after, being quite an expensive vehicle.

[snkjr]

I have been following the idling rule for my Duster 85 PS religiously, though I might have missed out on a couple of occasions. I idle before setting the car in motion and I idle before turning the engine off after halting. However, these days I can hear the whir/squeal of the turbo rather distinctly. It's certainly more prominent than it originally was. I can tell it's the turbo whirring as the sounds starts at around 1800-1900 rpm and goes up to 2000-2100 rpm after which it tends to quite down/settle down. Is this something I need to be concerned about? It sure does get me worried, but since this is my first turbo-charged vehicle, I'm not sure whether the whir/squeal (more whir than squeal) is normal and expected or abnormal and unexpected.