[vikram_d]

Originally Posted by bbhavan

Thanks for the link.I went through it.

But one question. How do the driver know that the turbocharger is functioning?

Pls. explain

bbhavn

The simplest thing that will tell you that the turbo is not working is loss of pickup. This method is applicable to both petrol and diesel vehicles.

In addition to this in a diesel vehicle the exhaust will emit thick black smoke which is basically un-burnt diesel.

[bbhavan]

Thanks Sagar and Vikram,

Now onwards I will watch for that sudden rush of adrenalin from the engine!!.

But what defines that particular RPM level which helps to create that boost?
I understand that it will vary from vehicle to vehicle.

1. What about Innova?

2. Also I understand that this turbocharger reduces the pollution level, by maximizing the efficiency of the fuel burnt. Is it correct?


regards,

bbhavan

[joey645]

Thanks GTO. Your post couldn't have come at a better time! Ive just picked up my first turbo charged car, and while the VW guys did ask me to keep it on idle, it wasn't until I read this post that I understood the reasons for it and the importance of doing this on a daily basis.

[vikram_d]

Originally Posted by bbhavan

Thanks Sagar and Vikram,

Now onwards I will watch for that sudden rush of adrenalin from the engine!!.

But what defines that particular RPM level which helps to create that boost?
I understand that it will vary from vehicle to vehicle.

1. What about Innova?

2. Also I understand that this turbocharger reduces the pollution level, by maximizing the efficiency of the fuel burnt. Is it correct?


regards,

bbhavan

The RPM at which the engine can throw out sufficient exhaust gases will define how quickly the turbo spools up and produces boost.

In the Innova I think the boost starts to kick in the 1800 - 2000RPM range. I'm not very sure of these numbers as it has been a very long time since I last drove the Innova even though I have one at home.

Your point number 2 is correct. Turbochargers do reduce pollutants in the exhaust gases.

[saurabhdadhichi]

As rightly mentioned already by GTO about not just keeping a tap on turbo but also on overall engine components operating temperatures.

In temperature conditions like 6-7 degrees celcius, my Maruti Swift diesel runs cold engine for more than 10 mins i.e the temperature indicator needle dont even budge for atleast 10 mins drive in such a scenario also one should be driving the car in a very subtle way and not accelerating aggressively. This will help in keeping not just turbo but also other engine parts durable owing to less stress on the engine components. Last but not the least one more benefit of driving in this way is that overall fuel economy is better than driving aggressively when engine is cold.

[SDP]

Any idea if the 30 second idling would apply to commercial vehicles as well? I mean, do the BEST buses in Mumbai have turbo-chargers? I have seen BEST buses revved to glory every morning, I guess in an attempt to warm up the engine. Wouldn't that be hurting the engine? Any idea?

[SKavuri]

Originally Posted by Rehaan

This is one of those things that doesn't hurt to do, regardless of the situation. It's good for other components of your car too.

Personally, i hate sitting in the car for upto a minute after reaching my destination. So to avoid that, I follow a simple rule which is just as effective: drive at low RPM (and low load) for the last minute of my journey. If I've been driving spiritedly, then I increase the time spent driving slow at the end.

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Intercoolers are found in some turbocharged cars. Don't make the mistake of thinking that these are for keeping your turbo cool. They are for cooling the air that comes out of your turbocharger, before it goes into the engine intake.


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For those of you who are wondering what this turbo bearing looks like and why the oil is so important: In a majority of turbochargers in Indian cars, the metal shaft of the turbo doesn't use what most people typically consider bearings (ie. ball bearings). It's just two highly smooth metal surfaces rubbing up against each other, with only a thin film of oil as lubrication in between.

You can see these 'bearings' here, shown in golden-brown:
Attachment 1044249
Source

cya
R

I am surprised that the tiny bearings in the turbo-charger are actually hydrodynamic type. Perhaps it is due to the high temperature and RPM but I would take it for granted that special high-temp rated anti-friction bearings would have been designed by now for such applications. Even hydrodynamic bearings are difficult to design and make for such small shaft diameters and high RPMs. The selection of oil grade is also very tricky because of the high temp temperature bandwidth the oil needs to lubricate in (exhaust temp on the turbine side and just above ambient temp on the charger side) So, why hydrodynamic bearings?

Even in real-world turbines (the big ones), it is a recommended practice to keep running the oil system for some time after shutdown (normally an hour or so). The intent is to cool down the bearings. The rotor is also racheted during this time.

Is there normally an oil cooler in the oil-circuit?

[Jeroen]

Originally Posted by SKavuri

Even in real-world turbines (the big ones), it is a recommended practice to keep running the oil system for some time after shutdown (normally an hour or so). The intent is to cool down the bearings. The rotor is also racheted during this time.

Is there normally an oil cooler in the oil-circuit?

On big maritime diesel engines, especially the very large two stroke one, the oil system for the turbos will typically be a separate circuit with at least two independent pumps, one as standby, and a large oil tank somewhere in the top of the engine room. The pumps ensure the oil gets pumped into the tank and then it's actually gravity that allows the oil to circulate through the turbo. The reason is that in case of a black out (loss of all electrical power) the turbo still gets lubrication through it's gravity fed tank. On these large diesel the turbo could be close to 1 m diameter spinning at high RPM's. Running without oil will cause damage within seconds, hence the tank and gravity fed system.

The one thing I have never been able to figure out, why turbo's on diesel/petrol engines can be so finicky when it comes to thermal shock. Take a gas turbine (i.e. a jet engine), in essence a very similar type of machine. Even higher temperatures, same issues with lubrication, seals etc.

There you start and you can go immediately to 100% power! (That is the reason gas turbines get used for emergency power generation, as propulsion on Navy ships, fire fighting systems. So we have all the technology to make it work, but somehow not on these relatively smaller and simpler turbo's. Maybe cost is a factor.

Jeroen

[headers]

Originally Posted by Jeroen

Maybe cost is a factor.

Yes Sir. Cost is a very important factor and consideration while designing the TC for any IC engine and its desired application.

Apart from cost, the desired engine rpm operating range, its optimum efficiency as well as the reliability of the design, projected life of the engine are some other parameters which decide the type of TC, its cooling parameters, bearing type etc etc.

[kutlee]

Originally Posted by vikram_d

Your point number 2 is correct. Turbochargers do reduce pollutants in the exhaust gases.

Vikram - I feel this is correct on lower rev range. In fact it is so good that it pumps out steam! If it is tuned to be rich on high rev range, then it might leave some black smoke!

[vikram_d]

Originally Posted by kutlee

Vikram - I feel this is correct on lower rev range. In fact it is so good that it pumps out steam! If it is tuned to be rich on high rev range, then it might leave some black smoke!

The vehicles fueling does not need to be so rich at high RPM's for street/daily driven cars that it throws out black smoke. Racing applications, maybe yes but not for daily drive cars.

[DDIS]

Have a Swift D (outgoing model) and follow the idling rule everytime.

My friend has a Fluidic Verna D 1.6 which comes with a VGT. Does having a VGT mean that idling is not necessary since VGTs do not have that turbo kick like the FGT on Swift D and deliver linearly? I believe the manual doesn't talk about the idling rule either.

I know that he otherwise does a slow move and relaxed run for 3-4kms.

[vikram_d]

Originally Posted by DDIS

Have a Swift D (outgoing model) and follow the idling rule everytime.

My friend has a Fluidic Verna D 1.6 which comes with a VGT. Does having a VGT mean that idling is not necessary since VGTs do not have that turbo kick like the FGT on Swift D and deliver linearly? I believe the manual doesn't talk about the idling rule either.

I know that he otherwise does a slow move and relaxed run for 3-4kms.

VGT's need to be spooled/cooled down more than FGT's because a VGT is almost constantly running at peak RPMs through out the rev range of the car.

[DDIS]

Thanks Vikram_d. I can pass on this information to my friend!

[SKavuri]

Originally Posted by Jeroen

The one thing I have never been able to figure out, why turbo's on diesel/petrol engines can be so finicky when it comes to thermal shock. Take a gas turbine (i.e. a jet engine), in essence a very similar type of machine. Even higher temperatures, same issues with lubrication, seals etc.

There you start and you can go immediately to 100% power! (That is the reason gas turbines get used for emergency power generation, as propulsion on Navy ships, fire fighting systems. So we have all the technology to make it work, but somehow not on these relatively smaller and simpler turbo's. Maybe cost is a factor.

Jeroen

From the discussion above, the reason for the idling is because of coking in lube oil, not thermal shock. We don't face this problem of oil coking in Gas Turbines because the lube system has a cooler and a temperature control system. The unit trips if the oil temp rises above the trip temp.

That was why my question - does a car have a cooler for lube oil? If so, there is no need for idling to avoid coking.

Just like GTs, even IC engines can go to full-load in a very short time. But the difference is that IC engines are not used in big utility power plants as the main power generator. They are used only as emergency back-up to aid black-start precisely for this reason - quick loading capability. The GTs are considered quick loading in comparison with Steam turbines, not in comparison to IC engines. (Imagine the time required for the steam boiler to go from light-up to working pressure).

But on second thought, if the oil can take the temperature of the engine cylinders without coking, it should be able to face the exhaust temperature without coking. Perhaps coking is not the reason for the idling.
When the temperature of TC raises or falls suddenly, the casing and impeller have different thermal expansions and may lead to seizure (the clearances are very small). This could be the reason for idling - not oil coking.
It logically also means that at the time of starting also (not just switching off) one has idle to slowly warmup to avoid seizure. Idling during starting also helps to circulate the lube oil to all engine lubricated areas before the engine is loaded.