[HIGHNOON]

Originally Posted by IndigoXLGrandDi

GTO,
I use Castrol CRB Turbo SAE 15W40 API CH4 as against the Tata Motors Ltd Recommendation of SAE 15W40 API CF4+. And I Replace the Engine Oil at TML Recommended 7,500kms and 10,000kms for Indigo LS (May 2004, 1,76,000+kms) and Indigo XL Grand DiCOR (May 2007, 90,000kms+), respectively.

Those ODO figures are impressive mate.
I go by 5000 km interval change ( or even less at times ) FOR MY INDIGO turbo LS.I manage 5000 km run in 3-1/2 months. I have used the CRB turbo too. Looking at your mileage , should i too stick for the 7500 k m company recommended interval. I almost always exceed the cf4 , so may i stick to 7500 km ? Because the oil seems to have not lost too much of its lubricity by then ( 5000k m).
And i stick to 5000 km for my petrol accent too with 60000km on the odo than the company specified 10000km / 6 months
Now that the oil is become so expensive , i feel i ought to.

[SPIKE ARRESTOR]

as far as i know the modern turbos RPM ranges from 40000 rpm to 170000 rpm when in full swing, now imagine something rotating at such high speed being suddenly switched off, this would lead to huge thermal shock loads in and near the turbo housing, hence in order to minimize this tendency it is advisable to idle the engine and then gradually shut it off, gurus please correct me if i am wrong.

[triedeverything]

I did ask the salesman who explained the features to me about the idling requirement. He just brushed it aside saying that modern diesels don't need this done. However, he told me to pump the cluthc 3-4 times before ignition everyday. The micro hybrid (start stop) mechanism does not allow you to idle for long. So the only options I have is to turn off the start/stop feature and/or use the methods explained above.

[GTO]

Originally Posted by HIGHNOON

Looking at your mileage , should i too stick for the 7500 k m company recommended interval. I almost always exceed the cf4 , so may i stick to 7500 km ?

Regular (mineral) oil = 5,000 kms oil change interval is just right. If you use synthetic, sure, stretch the oil change to 7,500 kms.

Originally Posted by SPIKE ARRESTOR

it is advisable to idle the engine and then gradually shut it off, gurus please correct me if i am wrong.

Based on the responses to this thread, I do practice the 60 second idle religiously. Irrespective of whether modern turbos require it or not, I'd rather be safe than sorry.

Originally Posted by triedeverything

The micro hybrid (start stop) mechanism does not allow you to idle for long. So the only options I have is to turn off the start/stop feature and/or use the methods explained above.

I guess you can switch the micro hybrid system off? I do remember a control for this. Thus, when idling, use that switch!

[amitk26]

Originally Posted by triedeverything

I did ask the salesman who explained the features to me about the idling requirement. He just brushed it aside saying that modern diesels don't need this done. However, he told me to pump the cluthc 3-4 times before ignition everyday. The micro hybrid (start stop) mechanism does not allow you to idle for long.

Brush aside whatever salesman told you M&M in modern Scorpio used to put a sticker 4-5 years back to idle for 1 min, when Turbo Diesel was new for them.

Why on earth Clutch should be pumped 4-5 times apart from exercising calf muscles ? never heard about it can Gurus throw some light.

[shramik]

In a rented Audi A4 in Germany, I saw that they have an oil reservoir fed by the oil pump, which lubricates the turbo. It looked a bit like a shock absorber tube. When the engine starts, the oil is forced into this tube by pressure and a piston is pushed out so the tube is filled. When you switch off, the reducing oi pressure transfers the oil back into the sump from this tube, thereby lubricating the turbo on the way out even when the engine is off. I estimate the capacity of this reservoir to be about 500ml to 700 ml. Has anyone seen something like this ?

Originally Posted by GTO

What have you got to lose? If you want to be on the safe side, let the turbo come to idle rpm before switching the engine off. We have sufficiently commented on how avoiding this practice can indeed lead to premature turbo damage.

[oss]

Originally Posted by SPIKE ARRESTOR

as far as i know the modern turbos RPM ranges from 40000 rpm to 170000 rpm when in full swing, now imagine something rotating at such high speed being suddenly switched off, this would lead to huge thermal shock loads in and near the turbo housing, hence in order to minimize this tendency it is advisable to idle the engine and then gradually shut it off, gurus please correct me if i am wrong.

The turbo spins on a shell bearing, and will continue to spin for some time, even after the engine is switched off, before it compeletely stops. Now most of the turbos (few exceptions like the Audi mentioned by shramik) are lubricated by simple gear pumps, which depend on the engine running to work. Therefore, as soon as the engine is switched-off the lubrication stops, with the turbo still spinning. The bearing & the residual lubrication can't handle the heat produced if the turbo is spinning faster.

That's is the reason for the recommendation to idle the engine for a minute, by which time the turbo stops spinning or atleast is spinning very slowly, and does not get damaged.

[Sprucegoose]

I saw a caution notice in a BEST bus today, stating that the bus has to be idled for 3 minutes before switching off the engine.
It was in marathi.
It also mentioned that because the turbocharger was spinning at a very high RPM, it needed to be idled so that the lubrication is not cut off suddenly.


quite cool....
the bus driver was looking at me funily while I was reading the notice...
then i told him that altleast he had a turbo, my car doesn't

[dilipkumar7278]

Toyota Fortuner manual clearly states that you have to idle for about a minute after spirited driving. So no harm in doing so. It also states to depress the clutch fully before starting the engine
Cheers
Dilip

[bantejas]

Spare me if this has been raised before or my question:
The mahindra scorpio hybrid manual states that at the signal, after 13 secs of idling the engine shuts off and the moment we press the clutch it comes off live again. Doesn't that hurt the turbo?

[SushilBajpai]

The Scorpio manual is pretty specific about idling it for a minute on each start up and shut down to spool up and cool down the turbo-charger.

I have seen no such recommendation in the Yeti manual.

Although at one place (buried deep within the pages) it does mention that after a hard long drive, it is recommended that it be idled for a minute before shutting down.

Does it mean one can drive straight off, albeit gently - particularly off a cold start.

What would hard long drive mean for the Yeti? When should one idle the engine for a minute?

Also if one was to drive the last five minutes gently - at RPM around 1000 - 1200 would one still need to idle? Or could one just turn off the engine?

I'd be interested to hear from the Skoda owners what do they do for their turbo-charged cars. They all appear to be similarly equipped.

[oxyzen]

-The logic is when your oil temperature is high, oil pressure is low. Turning off engine in such a state means during next startup you will have oil starvation.
-Also after it is switched off, it cools very rapidly. Result? Thermal shock.

This is more prevalent where oil temp. is high. And that is the Tubo.

So the main motive is to bring the oil temp. down.

[dhanushs]

I guess this is a very apt explanation.

The figure of a minute or two before shutdown was relevant for the older, non water cooled turbos. Yours ('86) should have water cooling, and thus only require a few seconds. Is this so? [Response:] Yes, it is. The reason the two minute cool down period was required is that so called 'first generation' turbos had oil cooling, but no water cooling. The effect of oil cooling is less, and thus these units ran MUCH hotter than later, water cooled turbos - after a long drive they could be glowing red! This is hot. And it can burn the oil. This does not cause a problem while the car is running, because the oil pump keep recirculating the oil around, so it doesn't stay in the turbo long enough to burn (and it has that nice oil cooler next to the main radiator as well). The problem is that as soon as you shut down the engine, the oil pump stops. If the turbo is still spinning, it has no pressurized lubricating oil. The oil that sits in the turbo stays there and can burn and coke. If solid sludge particles form in the turbo bearing (which is an oil bearing), they can score the bearing journals - kind of like your very own grinding machine inside the turbo.

Enter second generation turbo.These units have the same oil cooled bearings, but they also have water cooling - much like an engine has oil bearings and water cooling. The effect on the turbo is two fold: One, it runs much cooler - doesn't glow red or anything (the exhaust manifold might (read: does...), though - but that's a different story). Aside from that, the water keeps recirculating even after the engine is switched off, due to convection (i.e. hot water rises). Hence, the danger to second generation turbos is considerably reduced.

So, one would ask, what is the reason for the few seconds of idle after starting and before switching off? Simple. In the first few seconds after starting (even after the oil warning light is off!) the oil pressure is lower, and fresh oil may not have reached the turbo yet - and if you race the engine, the turbo will spin fast with insufficient oiling of the bearing - not good. Likewise before switching off: when the engine stops the oil pumps stops immediately. The turbo, however, may keep on spinning for a few more seconds if the engine was racing just before being switched off - simply because of inertia. So again the turbo would spin fast with insufficient oiling. This (and the 1st generation problems mentioned before) is the reason behind the different 'turbo pre- and post- oiler' systems.

Source: Engine-Turbo1

[Orko]

Do the new Lauras have the second generation, water-cooled turbos? It's a real pain sometimes to have to wait for a minute!

[SushilBajpai]

Thanks for the detailed explanation about why there are different post-start and pre-stop idling recommendations for different vehicles. From the forgoing I assume that Scorpio had first generation turbo - only oil cooled - while the Yeti and more modern machines have later generation which is cooled by both oil + water.

The Yeti manual then makes sense in my mind.