[humyum]

- I clean by air filter every 2000 km, It always gives out dust particles whenever its cleaned, so I assume, atleast some air flow is restricted. Change the air filter every 10 thousand km.

- Let it rip to high rpms once or twice in a week, clears the system out. At these times black smoke is observed for a moment or two after that not.

- Have cleaned EGR just once in 75 thousand kilometres, Don't touch something that is not broken, a high rpm burst drive once in a while surely helps keep things in order.

[leylander]

the issue of black smoke coming from the engine during free acceleration is because of a thing known as smoke limitation in the ECU.

during the programming/calibration of the ECU, there are parameters for the combustion like for a specific engine RPM and acc. pedal % what should be the air-fuel ratio value. generally for higher RPMs the air fuel ratio is higher thereby leading to proper combustion, but at the lower band of RPMs the air fuel ratio is more towards the stochiometric ratio or generally less than 2.
this is provided so that you don't feel sluggish at the initial burst of acceleration by supplying more fuel.

after all this, even though some visible black smoke comes through, the smoke is analyzed for its contents and it should pass the norms specified.

[Sheel]

I too thought that black smoke is an integral part of a diesel engine, whatever Car it maybe.

30 months and 22,500 kms later, my Car doesn't smoke. Nor at cold starts, nor under acceleration or nearing its top speed (not visible in the RVM)

The only precaution I take is, fill at most reputed pump I know of.

[rubbermeetsroad]

I am new on the forum so please expect some forum illiteracy and point it out for me to rectify
I just felt like I could add to the discussion here goes -
Black smoke from diesels is something that has been talked about so much that it has lost people's interest
Most of us have partially resigned to it as being the part and parcel of a diesel motor.
I want to stress that it should not be so and will also point out what you can do to avoid it
Start from inside out. So first it might be worn out and dilated nozzle s of the injectors which will mean more fuel to air ratio. If you compare to petrol diesel engines can stay running at tens of times the fuel air ratio. Almost 50 :1 ratio which would stall any gas engine, will keep the diesel engine ticking. Although it will be pushing out plumes of black smoke , which is the condition we are trying to diagnose
So the most probable cause for black smoke on high mileage diesels can be eroded injector nozzles. This can be confirmed when you take a removed injector under a microscopes.there are a number of good images on google to compare to.
Second culprit can be dysfunctional or bad bearings on the turbo. Visual inspection is the only way to confirm. But it is possible that if it just a laggy turbo you will probably see black smoke only while accelerating. This would mean a lagging Turbo.
Third possible thing to look into would be a faulty EGR valve. It is the part that keeps a blocking turbine from obstructing the exhaust and cause loss of performance. It is a kind of overflow and bypass valve combined into one
Make sure to rule it out as well. best way to isolate a faulty EGR would be to pay attention to your diagnostic codes. Also
A pollution control test can provide useful info abt the combustion quality,which is one of the many manifestation of all the above problems
But be careful that it is only a broad indicator and certainly not a confirmation of any of the three problems explained above.

Hope I have added some value to the discussion.
Best of luck and Godspeed!!!!

[CANPUSH]

I am not a technical person but here are my two cents that I have learnt while I owned a diesel Palio.

In any diesel car if you floor the throttle it will send out a black cloud loaded with soot. However, if you gradually press down the throttle there will be no issue at all. This phenomenon is common to all diesel cars, of all make, new or old.

This, I believe, has something to do with diesel technology. (Please correct me if I am wrong)

First time I came across this when I went for Pollution check after completion of one year of ownership. That time diesel cars were checked for pollution at full throttle. The car failed the test. Alarmed, I went to the workshop to check and get cleaned the injectors. There was nothing wrong with injectors I was told. To make me happy injectors were cleaned, diesel in car tank was tested. Everything was ok. Then one of the senior mechanics told me not to floor throttle in a jiffy. It worked.

May be some learned members can throw more light on this.

[msaudf]

Originally Posted by CANPUSH

I am not a technical person but here are my two cents that I have learnt while I owned a diesel Palio.

In any diesel car if you floor the throttle it will send out a black cloud loaded with soot. However, if you gradually press down the throttle there will be no issue at all. This phenomenon is common to all diesel cars, of all make, new or old.

This, I believe, has something to do with diesel technology. (Please correct me if I am wrong)

the amount of smoke or soot that appears when a diesel engine is under load or given full throttle is mainly due to the lack of sufficient air for a clean combustion during the initial seconds of full throttle. as you mentioned during gradual throttle inputs there is less or mostly no smoke. This deficiency of air is compensated by a turbocharger, again the turbo kicks in at a slightly higher rpm than idle ranging from 1000 to 1500 sometimes even 2000 rpms. During the time the engine takes to get to this stage the fuel injection pump sprouts out more fuel that can be burnt with the amount of air that there is inside the cylinders leading to incomplete combustion and therefore soot or smoke. In my opinion turbo chargers are best suited for gasoline/petrol engines and diesel engines should be fitted with superchargers or in the case of smaller engines belt driven turbochargers.

If I had a fully functioning machine shop and proper tools I would embed a turbocharger that is linked to the engine and driven by the timing chain/belt. But you know just a thought to get rid of the smoke and show the true potential of an oil burner.

[amitpunjani]

Originally Posted by msaudf

the amount of smoke or soot that appears when a diesel engine is under load or given full throttle is mainly due to the lack of sufficient air for a clean combustion during the initial seconds of full throttle.

If I had a fully functioning machine shop and proper tools I would embed a turbocharger that is linked to the engine and driven by the timing chain/belt. But you know just a thought to get rid of the smoke and show the true potential of an oil burner.

I really like your views, this actually gives food for thought, why aren't diesel engine supercharged?

I have seen multiple cars from Nissan stable giving out emitting black soot vis a vis any Fiat engine. Any specific reason?

[msaudf]

Originally Posted by amitpunjani

I have seen multiple cars from Nissan stable giving out emitting black soot vis a vis any Fiat engine. Any specific reason?

Thank you for your kind words but I'm no expert but a mad engineer. So take my words rather lightly.

Now to your Q:

The Nissan sunny and micra use the DCi from Renault, I'm sure you already knew that. Well, these Renault engines have some turbo lag coupled with an incorrect or improper air-fuel mixture that causes the soot during the initial throttle inputs. A decent diesel tuning box or chip can reduce the soot and also give you more power. These DCi engines are in my opinion one of the best that is out in India in this segment, infact better than the Multijets in terms of longevity fuel efficiency. You can rev the nuts of the engine and it will still keep going.

The Fiat Multijets are simply better tuned and have lesser turbo lag hence no or less soot. But, I have heard they develop issues at higher mileages. I think they've squeezed just too much power from 1300 cc.

Also please keep the air-filter in check as a clogged air-filter will contribute to excessive soot. A MILD blast of air twice a month will do the trick.

[amitpunjani]

Originally Posted by msaudf

Thank you for your kind words but I'm no expert but a mad engineer. So take my words rather lightly.

Now to your Q:



The Fiat Multijets are simply better tuned and have lesser turbo lag hence no or less soot. But, I have heard they develop issues at higher mileages. I think they've squeezed just too much power from 1300 cc.

Also please keep the air-filter in check as a clogged air-filter will contribute to excessive soot. A MILD blast of air twice a month will do the trick.

Thanks for the clarification buddy. Yes i am aware Renault engines are Dci engines, but then i fail to understand how ARAI could pass such engines.

Also could you pls. elaborate "A MILD blast of air twice a month will do the trick"

Regards

Amit

[msaudf]

Originally Posted by amitpunjani

Thanks for the clarification buddy. Yes i am aware Renault engines are Dci engines, but then i fail to understand how ARAI could pass such engines.

Also could you pls. elaborate "A MILD blast of air twice a month will do the trick"

Regards

Amit

The ARAI's approval on engines with respect to pollution is based on the CO emissions CO2 emissions Hydrocarbon emissions and some others.
AFAIK these are the parameters that are looked into while performing a normal Pollution Check in all vehicles.
DCi engines would have come through with lower levels of the recommended max figure hence they have been passed.

"A MILD blast of air..." means cleaning the filter with compressed air (i was trying to be cool).
I did mention mild in caps because a full blast will damage the filter exercise caution!

An addition to my earlier post to reduce soot in DCi engines would be a better (lesser restricting) Air-filter.

[amitpunjani]

Originally Posted by msaudf

The ARAI's approval on engines with respect to pollution is based on the CO emissions CO2 emissions Hydrocarbon emissions and some others.
AFAIK these are the parameters that are looked into while performing a normal Pollution Check in all vehicles.
DCi engines would have come through with lower levels of the recommended max figure hence they have been passed.

"A MILD blast of air..." means cleaning the filter with compressed air (i was trying to be cool).
I did mention mild in caps because a full blast will damage the filter exercise caution!

An addition to my earlier post to reduce soot in DCi engines would be a better (lesser restricting) Air-filter.

Buddy what i would suggest not to clean the filter with compressed air specifically the for MJD engines as the air filter is too delicate. There are chances when you blast the compressed air there chances of rashes coming out and getting stuck in the turbo.

I normally take out the filter and strike against the wall few times to remove dust.

Cleaning with compressed air is good idea, but the mechanics hardly know the difference b/w mild and strong blast of compressed air.

Regards

Amit

[Arch-Angel]

The reason why most consumer engines arent supercharged is because some amount of power is used to run the supercharger itself. The more powerful the engine, the more the gains from the supercharger. Anything below 150 bhp is better off with a turbo which is what i feel. Also turbos have one good thing going for them. Turbos run off exhaust gases whereas superchargers run on engine power and needless to say, the last thing our aam aadmi wants is poor mileage from a puny engined car. Also, if you look at the majority of the turbo charged cars rolling from the assembly lines of many of the manufacturers, you will find that they arent tuned for power, its efficiency they are after, which is the ever elusive 'eta'.

[msaudf]

Originally Posted by Arch-Angel

The reason why most consumer engines arent supercharged is because some amount of power is used to run the supercharger itself. The more powerful the engine, the more the gains from the supercharger. Anything below 150 bhp is better off with a turbo which is what i feel. Also turbos have one good thing going for them. Turbos run off exhaust gases whereas superchargers run on engine power and needless to say, the last thing our aam aadmi wants is poor mileage from a puny engined car. Also, if you look at the majority of the turbo charged cars rolling from the assembly lines of many of the manufacturers, you will find that they arent tuned for power, its efficiency they are after, which is the ever elusive 'eta'.

Bang on ArchAngel, That is the exact reason Superchargers aren't used in small diesel engines, I have also heard that the turbo charger's presence increases the exhaust back pressure and that it was a good thing. What do you think is the advantage of having increased back pressure?
I agree that turbo's are fitted not for power but for efficient burning of fuel that will result in lower pollution. Power is only a byproduct we enjoy. But then we turn the tables around and use the turbo to our advantage by chipping our cars

[Arch-Angel]

Originally Posted by msaudf

. What do you think is the advantage of having increased back pressure?

In my opinion, slightly higher backpressures will help in the following ways.

1. Firstly, the higher backpressure will ensure a slightly higher volume of gas to be sent to the turbo which will bring it up to its operational rpm faster, which would mean slightly improved low end torque. However, the same low end torque can be brought about by a smaller turbo.

2. This back pressure coming out of the exhaust manifold/headers, if the exhaust system is restrictive in design, will cause a lot of thie exhaust gas to get pushed back in through the exhaust valve if the pressure difference between backpressure and the cylinder stroke- out(exhaust cycle) pressure is positive, which would mean the engine would be breathing less and therefore would bring down the efficiency of the engine.

3. If the back pressure is low, the power delivery becomes very linear and will have the engine breathing a little more freely, since the scavenging of exhaust gases is better and therefore, you will lose a bit of the low end torque but will gain quite a bit in the higher end.

4. This is exactly why some crazy drivers fit a misfiring system which causes a small 'pop' in order to spin the turbo up faster for a better low end torque delivery but at the same time, have a good high end since the exhaust isnt very restrictive.

I might not be spot on with my analogies and would like the experts to comment on this because i feel as though my mind is clouded with soot

[rpads1]

I had this problem of black smoke recently on my Siwft LDI and happened to read up this thread then. The black smoke would come on hard acceleration mostly , especially when going up a gradient. I thought it must be something typical to diesel but showing up now . Also tried different Fuel Stations.

Thought I'd update all on what the problem was .

It became worse over time (4-5 weeks) and I got the time to visit the service centre Bimal, Mahadevpura. They quickly diagnoised it to be something to do with the turbocharger/intercooler. On opening things up they nailed it down to a cut hose pipe on the intercooler . That explained why black soot only on hard acceleration (when the turbo kicks in ), in fact only then I did realise that I was suffering from lock pickup at higher speeds on each gear. The service technician did mention that over time the car would have not gone above 60 .
Post the Intercooler hose pope replacement things are fine and no soot at all , however hard I drive.