Why do diesels smoke so much

Especially with FOOT flat down

Nige

 

Diesels smoke because they are diesels. It's the fuel that does it and they ain't enviromentally friendly

 

but 50mpg is cool

But why do some smoke less

My audi seems ok unless you BOOT it and hold it

Sat behind a newish Chrysler voyager that was pumping shite out

NIge

 

i thionk its because of the carbon build up, some may build more carbon up than others in he exhaust, but mostly turboo diesels smoke more because the air is getting forced out harder thus blowing more carbon out

 

I've got a lightly modded 206 hdi (130bhp, remapped, k+n panel filter, full exhaust) and mine dont smoke to bad in general

The only time it smokes is if u floor it off boost, and thats because theres loadsa un burnt fuel

 

All diesels smoke under load, they are effectively oil burners, they use compression to burn it as opposed to spark. The new cats and stuff can help with getting rid of some of the shite. Might've been cold or rich also

 

Diesel is difficult to combust. WHat u see is reminents of incomplete combustion. Modern diesels use very high fuel pressure in order to get the power they do. Sometimes, a little too much is injected, and it's equivelant to running a slightly rich mixture - but it's far more noticeable with diesel. You can tune modern diesels to quite high power outputs by increasing the fuel pressure - but u start to get lots of visible smoke.

 

Diesels NEVER run rich!

They smoke more due to the fact that you spray diesel into really hot air. The only point of combustiong is when air is mixed with the diesel...

So you inject very hard (high pressures and small nozzels) to make the spray as fine as possible. But you are still relieing on air movement to mix the air and fuel so it burns.

Some engines smoke less than others for one main reason - combustion chamber design!!

Alex