Flooring a diesel to clean the exhaust system

I don't know if it's a legitimate advice or just a legend, but does it make sense to take the truck to the highway every once in a while and floor it hard to 'burn off the excesses of exhaust gunk built-up'?

One should see a black cloud of smoke/ash flying out of the exhaust when this is done, they say. I heard this from some friends and even an independent LR mechanic, who said to do it once a month with the engine warm.

If this is true, could You please share Your view on how to do it and what are the benefits?

As I understand it, the gas peddle needs to be pressed very gradually to prevent the massive inflow of fuel which when will be converted into black smoke from not getting enough air in the first milliseconds. And if this is correct, then should there be any black ash cloud coming through the exhaust? Or would the gunk be burnt so gradually that there should be no black smoke?

Hope the wording is not too messed up

I don't know about cleaning the exhaust but a good run helps keep the valve seats clean, especially if the vehicle usually only does short, stop start journeys.

Col

Modern particulate traps need good hot decent run routinely to assist (though in theory the most modern ones will self clean reliably .....sort of....). Defender ain’t that sophisticated - I’m sure a good hot blast cleans the pipes a bit, but wouldn’t get too fussy about throttle control and fuelling, just do it! Others may have better thoughts.... Cheers A

vehicles fitted with a dpf can block over time if vehicle is used for cold short runs or an engine issue , a diagnostic unit has a program that runs the engine hard so exhaust temps reach about 600 degrees (iirc)for a few minuets ,it leaves a carbon stain on the floor,shouldnt be an issue with a good performing engine in a vehicle that gets thoroughly warmed up on a decent run reasonably regular

If it is an older land rover you would see more of an improvement with a couple of bottles of injector cleaner and a good length run to get everything hot. This will improve the internal condition of the engine, but on an older land rover the exhaust is just a steel tube so is nothing to worry about.
If it is a newer one with cats and possible a dpf then the exhaust system will need to get up to temperature to ensure any carbon deposits are burnt off, but a long run at motorway speeds should do this, you do not need to bury the throttle in the floor and push hard to achieve this.

Stock_90_TD5_SW said:

I don't know if it's a legitimate advice or just a legend, but does it make sense to take the truck to the highway every once in a while

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Yep, sure does, as Col says in post #2

Stock_90_TD5_SW said:

and floor it hard to 'burn off the excesses of exhaust gunk built-up'?

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Nope. waste of time, ( or worse ) - as mentioned in posts 3 & 4, you're trying, ( and you will fail - read on!) to re-create the situation within a modern DPF ( not fitted to your TD5 ) - this requires the filter to be at 600 C ..... good luck with trying to get your whole exhaust system to 600 C ... not least of your problems will be the requirement for a new engine, which will have melted by the time the centre box is anywhere near 600 ! ( Most alloy cylinder heads are hardened .... and will Anneal at about 720 Centigrade )

The cynic in me might even suggest that a garage will promote this sort of carp to get some extra work ....

Stock_90_TD5_SW said:

One should see a black cloud of smoke

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.... Which is unburnt fuel .... so, the happiest person alive will be the local filling station owner

If you are ever unfortunate enough to experience a (DPF) re gen cycle on a large modern diesel ( big truck ), then you'll probably notice the smell rather than anything else - certainly, IME, no smoke .... ( it would rather defeat the object - the filters are supposed to trap the fine particulates - NOT let them out )

Unfortunately, there is a lot of confusion about the differences between catalytic converters and DPF's .... despite the fact that the info is out there on the web - for example, have a nosy at the wikipedia entries for each...

Its a diesel and diesels like to be worked, pussy foot them around trying to save fuel is just asking for trouble no matter how old or new it is.
Basically rag its arse off every now and then

lynall said:

Its a diesel and diesels like to be worked, pussy foot them around trying to save fuel is just asking for trouble no matter how old or new it is.
Basically rag its arse off every now and then

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What I like to call " an Italian tune up"....

Always go for one just before the MOT......even if it does not need it...LOL

Cheers

neilly said:

What I like to call " an Italian tune up"....

Always go for one just before the MOT......even if it does not need it...LOL

Cheers

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i swear by an italian tune up.
You need to get the engine good an hot, and be certain your cambelt is up to snuff though......

its best to give it full throttle for maximum smoke output just as you pass a cyclist

Does not apply to your TD5 as there is no diesel particulate filter (DPF) just use it and enjoy it anc dont worry about it.
You will just waste your expensive diesel.

Scooby22 said:

Does not apply to your TD5 as there is no diesel particulate filter (DPF) just use it and enjoy it anc dont worry about it.

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Actually apllies to all diesels no matter how old.

EeEk said:

its best to give it full throttle for maximum smoke output just as you pass a cyclist

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Or a Wayne Kerr in a convertible Audi hassling you....

Thanks guys, from all this feedback I conclude:

1. regular flooring on the highway is reasonable
2. getting black smoke is not the goal

My questions are:

a. should I hold high stable revs for 30-60 seconds or more (lets say 90-95 kmh in 4th gear)?
b. is there any importance to 'accelerate aggressively' without getting too much black smoke?

In other words, what am I aiming at - when are those carbon deposits actually burnt?

The air flow through the eggsauce at 70mph when driving normally is enough to clear out any soot in the pipe.

Just google principles of Italian tune up

Short journeys where the engine doesn’t get hot for long is not great, just a long journey at operating temperatures is good enough.

My fuel gauge fogs up after a while, when it’s heated up enough to de-fog I know my engine is thoroughly warm lol

Thanks, flat! Will google Italian tune-up!

Good indicator You've got there

I've had quite a few cars which I've bought that have been used around town. I also used to take my soon to be ex wife the garage van and my mothers cars on a good run.
All of them always felt like they reved better and more responsive and powerful after a 40 mile motorway trip to work.

One car a petrol Audi turbo had been pootled around in that much the turbo waste gate was seized part open. A good load of anti seize and a ragging later and it went like stink.

Not saying I agree with this bloke or not, just happened to see it while searching for something else.



As far as I'm concerned a good dose of injector cleaner and 3 or 4 miles at high revs works for me on my 200Tdi 90.