Diesels accelerating - big clouds of black smoke- explain??

[rfn]

Soot built up in the exhaust which is burnt off when a load of hot gases are thrown down the exhaust. Usually happens when the engine is driven gently for a while then hard acceleration.

[8400rpm]

My Volvo does it.

It's either soot and ste from the exhaust that builds up, being blown out. Usually pre-DPF cars (like mine).

Or it's unburnt fuel, as the car is running a tad, or a lot, rich. Sometimes a boost leak.

[LuS1fer]

They all bloody do it, old or new. Hate them.

[HellDiver]

Bad remaps can leave too much fuel being injected for the amount of boost available, or intercooler heat saturation can also lead to "reek".

Mostly it's just a build-up of soot in the catalyst.

[Graebob]

I love it when there are traffic wombles plodding along at 60mph in L1 and all the 1.9 VAGmobiles slow right down panic and stamp on the breaks, then 200m past the wombles boot it back up to 80+. Must be foggy for those HATO warriors

[Munter]

As I understand it. To make the most power a diesel "over fuels" a lot. That excess fuel doesn't burn properly as theres no oxygen to mix with it. And you get soot.

Something like when it's not sooty, you're only using about 1/2 the oxygen to burn all the fuel. More fuel to less oxygen = more soot.

(No expert. But had a commentator try and explain it at a VW race with the Diesel van....!)

[Graebob]

Also clicky for a demonstration of unburnt diesel fuel.

[Dupont666]

so what about the Powerstroke, Cummins and Duramax engines that get tuned to silly horsepower?

Is that too much fuel dumping?

Is there anything that could be done to stop it?

[Hugo a Gogo]

mine never does it, must be regularly cleaned out with right foot action

[y2blade]

the first time I booted mine she coughed out quiet a lot of black smoke...but since then she has run clean for the 2500miles since

I guess the answer is to "force" yourself to let her stretch her legs properly every few miles

oh well

Hugo a Gogo said:

mine never does it, must be regularly cleaned out with right foot action

likewise

Edited by y2blade on Thursday 2nd September 10:30

[Rob P]

My Passat does it all the time, I find it embarrassing to be honest. It's not exactly a subtle way to make progress!

Saab TTid never did it at all.

[rudecherub]

Dupont666 said:

so what about the Powerstroke, Cummins and Duramax engines that get tuned to silly horsepower?

Is that too much fuel dumping?

Is there anything that could be done to stop it?

Yes it is.

Banks over in California run big numbers and no smoke, it's about getting the mix of fuel to air correct.

http://www.youtube.com/watch?v=Qkru4au8GqI

http://www.bankspower.com/home

[Deva Link]

Mine (C270CDi) does it very noticeably when I've cruised up the M6 and then have to boot it from standstill to get on to the fast flowing roundabout at the exit.

[Munter]

Dupont666 said:

so what about the Powerstroke, Cummins and Duramax engines that get tuned to silly horsepower?

Is that too much fuel dumping?

Is there anything that could be done to stop it?

To stop it. Use petrol.

I'm not sure it is "too much fuel dumping". If what you are after is peak performance from the engine, you have to accept the over fuelling and soot. Cars have regulations about black smoke (part of the MOT test as well), and as such try to make the best power they can while not making too much smoke. Hence the egr valves.

[Torquey]

I've never understood when you see some of the sh!te that comes out of diesels how they are so much cheaper on tax?
(well I'm sure the answer is quite simple but i've never bothered to think about it to be honest).

Surely these antisocial engine farts are far more polluting than a petrol engine?!

Edited by Torquey on Thursday 2nd September 10:43

[Munter]

Torquey said:

I've never understood when you see some of the sh!te that comes out of diesels how they are so much cheaper on tax?
(well I'm sure the answer is quite simple but i've never bothered to think about it to be honest).

Surely these engine farts are far more polluting than a petrol engine?

PM10 pollution.

Stay out of the city!

[V88Dicky]

Torquey said:

I've never understood when you see some of the sh!te that comes out of diesels how they are so much cheaper on tax?
(well I'm sure the answer is quite simple but i've never bothered to think about it to be honest).

Surely these engine farts are far more polluting than a petrol engine?

Depends on what you class as 'pollution'.

CO2 unfortunately is classed as pollution these days, and taxed accordingly.


True air quality of course, is about particulate contamination, aka proper pollution.....smog.

[Dupont666]

V88Dicky said:

Torquey said:

I've never understood when you see some of the sh!te that comes out of diesels how they are so much cheaper on tax?
(well I'm sure the answer is quite simple but i've never bothered to think about it to be honest).

Surely these engine farts are far more polluting than a petrol engine?

Depends on what you class as 'pollution'.

CO2 unfortunately is classed as pollution these days, and taxed accordingly.


True air quality of course, is about particulate contamination, aka proper pollution.....smog.

I used to enjoy racing chavs in my 306 DTurbo when it had been stood for a while and needed a clean... turbo spools up and then it pulls its party piece... soot screen... cue chavs coughing and gagging... cue me coughing and not being able to breath due to laughing so hard!!

God I miss tank...

[paulshears]

My brothers Caddy pickup didn't chuck out too much smoke when it tuned up from 75 bhp to 116 bhp



Chucks out very little visible smoke now that he runs it on a mix of cooking oil & diesel

[Dupont666]

paulshears said:

My brothers Caddy pickup didn't chuck out too much smoke when it tuned up from 75 bhp to 116 bhp



Chucks out very little visible smoke now that he runs it on a mix of cooking oil & diesel

If running even 4 times the power it can be quite bad, think 10 times the blackness in that photo