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Old 27th July 2006, 05:03   #1
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Default Decarbonizing your diesel car silencer at home

Many times you must have gone to the workshop. complained about pickup/black soot etc., problem and gotten charged 200-300rs for silencer decarbonizing.
This process need not be done by professionals, you can do the same thing at home too with almost similar results.
To see if your silencer needs cleaning first observe the smoke from the tail pipe. If at idling you have coloured smoke, then this could be a problem with your settings
Blue smoke : Rush to the workshop
Black smoke : Running to rich
white smoke : Running too lean(?) Dont know for sure.

Anyways if you dont have any significantly visible smoke, then rev up the engine and see of black smoke comes. This will be thick black smoke. Revving hard for some time will get rid of it, but this means you have only blown away the loose soot. If soot has been depositing in your tailpipe, there is lots still stuck.

So now we come to the actual step of cleaning. Be warned, this is not as efficient as removing the tailpipe and washing it with water under pressure, but still it will give you results close to that.

First park your car on an almost level surface with the rear of the car around 5cm higher than the front. Make sure that under no condition the tailpipe end should be higher than the point where tailpipe joins the engine. If thats the case you are looking at an expensive bill. Scared? well then park on a completely level surface. Also make sure that the area is disposable, you do not want to destroy your garden/porch with this, do you?

Next get a garden hose and "pour" water into the tailpile. Remember, do not force water, just pour, let gravity do the job, if you force water in you are asking for trouble. If the garden hose is thinner than the tailpipe considerbly you are safe.

Do this till water starts coming out of the tailpipe.
Now start the engine and revv up hard. You should see very very black water coming.
Now without switching of the engine, pour more water into the tailpipe. Careful water can be hot as it comes out. Then rev up again. Repeat this until the water is almost clear.
This process can take almost 10 min, but the benefits are great.
A decarbonized silencer means no more failing PUC checks and better pickup and FE.
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Old 27th July 2006, 07:52   #2
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Yup i agree, i get this done once in two months, and my car is generally devoid of any smoke.

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Old 27th July 2006, 10:18   #3
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used to get this done with my previous car (fiat uno diesel) and it works great
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Old 27th July 2006, 13:10   #4
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It is really a simple and effective procedure!!!

I've got a metal bend pipe fitted near the engine end of the silencer assembly... When I want to decarbonise it, I just open the nut and push the water hose pipe into this bend pipe... Once the water starts flowing out, pull out the hose, screw the nut back on and start the engine... Works perfectly every time!

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Old 27th July 2006, 20:26   #5
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Most garages spray pressurised water into the tailpipe, start up the engine, and rev it up to dispose the soot and water. This's usually done when the car's serviced. But there's a small downside; the baffle plates and casing of the canister/muffler, rusts pretty soon if this technique is applied regularly...
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Old 27th July 2006, 21:05   #6
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Is this something that only needs to be done for deisels?

I have never heard of this being done for petrol cars... I have driven my car (MPFI petrol) over 40Kkm (car has done 80Kkm total) but the amount of soot in the tail pipe is negligible. (Used a high tech measuring device... "Index Finger")

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Old 27th July 2006, 21:20   #7
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@turbo_c: Yup, done ONLY for diesels (the title says that too), since they have a far higher HC output. Used to do this regularly on my previous diesels, JUST before getting the PUC done......

For diesels, you don't even need the "High Tech Measuring Apparatus". If you can see (which is a boon while driving), you shall detect the black emissions..
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Old 27th July 2006, 21:52   #8
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Quote:
If you can see (which is a boon while driving), you shall detect the black emissions..
Wireless transducer!!!
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Old 27th July 2006, 21:56   #9
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Quote:
Originally Posted by tsk1979
[...]
Many times you must have gone to the workshop. complained about pickup/black soot etc., problem and gotten charged 200-300rs for silencer decarbonizing. This process need not be done by professionals, you can do the same thing at home too with almost similar results. [...]
Anyways if you dont have any significantly visible smoke, then rev up the engine and see of black smoke comes. This will be thick black smoke. Revving hard for some time will get rid of it, but this means you have only blown away the loose soot. If soot has been depositing in your tailpipe, there is lots still stuck.
[...]
Now start the engine and revv up hard. You should see very very black water coming.
Now without switching of the engine, pour more water into the tailpipe. Careful water can be hot as it comes out. Then rev up again. Repeat this until the water is almost clear.
This process can take almost 10 min, but the benefits are great.
[...]
(My emphasis in the above quote).

My car manual says that revving hard in neutral is bad for the engine (as is prolonged idling). I wonder if the professionals you refer to above also use the same method? If they use more sophisticated methods, I might just prefer to shell our Rs. 300 and get the job done by the pros -- if I had a diesel car, that is. Although I doubt if our mechanics (even in authorized garages) will respect such rules -- quite likely that they will violate every procedure during each service.

Last edited by rks : 27th July 2006 at 22:02.
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Old 28th July 2006, 01:14   #10
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Quote:
My car manual says that revving hard in neutral is bad for the engine (as is prolonged idling). I wonder if the professionals you refer to above also use the same method?
Now why does this sound strange to me??
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Old 28th July 2006, 01:21   #11
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There is a difference in revving hard and redlining. Prolonged redlining is bad for engine because its running at its peak stress state.
now if you are doing top speed in a gear, or revving at the same rpm in neutral, just being in neutral wont harm your engine any more that being in gear will.
Operating any engine at the limits of its performance will reduce engine life, even more so if your engine has not been run in.
But if you see a lot of soot getting deposited even before your engine is run in, its time to change your Fuel station.
Soot comes from unburnt hydrocarbons, and in most cases the reason is adulterated fuel.

About the prolonged idling part, I dont buy it. Would some guy who has actually worked on cars(Psycho/viper etc., care to elaborate) clarify wether idling for long periods, i.e. 10min or above will damage the engine? If so why?
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Old 28th July 2006, 01:31   #12
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Quote:
Originally Posted by nitrous
Now why does this sound strange to me??
My manual says that racing the engine (to warm it up, for example) is bad for it. So is prolonged idling. This may be for my Santro, but I think it applies generally. I personally would prefer the method used by the pros -- i.e., remove the tailpipe, clean it and fix it back. That way you avoid unnecessary carbon deposits and wear and tear on your engine. That is just my guess, I could be wrong.
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Old 28th July 2006, 01:53   #13
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Quote:
Originally Posted by tsk1979
[..]

About the prolonged idling part, I dont buy it. Would some guy who has actually worked on cars(Psycho/viper etc., care to elaborate) clarify wether idling for long periods, i.e. 10min or above will damage the engine? If so why?
I will check what my manual actually says tomorrow and get back. As of now what I remember is that lengthy idling reduces the life of the engine oil -- so maybe it affects lubrication. But I don't think that idling for 10 mts is a big problem. Still I am not comfortable with your method for reasons in my previous post.
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Old 28th July 2006, 14:19   #14
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The basic reason for not recommending high revs at idle, is engine cooling. When the engine revs at high R.P.M's while the car is stationary, the radiator fins are not getting enough airflow to cool the coolant passing through the cores. Hence, revving the car upto, say, 5000 R.P.M at idle will cause more internal tempratures and overheating, than if you had revved to 5000 R.P.M at 130 kmph.

Same case for prolonged idling. You'll notice that the engine remains calm at high speeds, but when you counter traffic after a high speed stint, your coolant boils up, and your engine is much more stressed due to high temperatures.
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Old 28th July 2006, 15:35   #15
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The reason given by veyron1 sounds right and explains why my manual classifies extensive idling as "severe driving conditions" under which the engine oil should be changed every 5000 kms (as opposed to 10000 kms for just highway driving). Probably the higher internal temperatures under extensive idling reduces the life of the engine oil.

Last edited by rks : 28th July 2006 at 15:41.
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