What's the real deal with diesels that blow black smoke? What is the real cause of it? Is it good, bad or none of the above?

 

Black smoke is unburnt fuel. Diesels make power based on the amount of fuel they inject. When you start making big power there isn't enough air (boost) to burn (clean up) all the fuel, so the excess comes out in the form of black smoke. Nothing bad about it, some guys actually LOVE it,

 

Could you just make the intake flow better to help burn the excess fuel?

 

That's what more boost would do, if you have enough turbo to support it. Most of the time they run out of turbo, but it will still more more power as you increase fuel, but it spits out more black smoke.

 

What is the reason for the power increase by just adding fuel? I'm so stuck in the world of gas motors that some of this diesel stuff just doesn't make any sense.

 

Diesel work WAY different then a gas motor, they are fuel throttled. The more fuel you inject, the more power they will make. There is no air metering devise like a TB on a gas motor, you can't run a diesel lean, you take away fuel the motor slows down, you add fuel it speed up. The more fuel you add the more power it makes. The turbo helps add air so it doesn't get too rich to a point where adding fuel doesn't increase power. They are a whole different animal.

 

So how does it make more power even though it's not burning any more fuel? Sorry if these questions seem stupid but I just can't grasp the fact that the black smoe means more power. Seems to me that a bigger turbo and more boost would be better than just more fuel.

 

It still burning more fuel, it's just not burning it completely or as efficiently, and the excess or not completely burned fuel comes out as black smoke. More boost is better, but most single turbos run out of boost around the 35psi mark and then you need to compound with a second turbo so you can get even more boost. But what do guys do when they have more available boost? Add more fuel so it black again. Thats just the way they like to tune.

Banks is real big on the you don't have to have black smoke to make big power, thats the way they try to build and tune there stuff to make as little smoke as possible.

 

I was under the impression and have heard from some people and companys, that all though it does make more power when dumping more fuel it isn't good for the cyclinders. Is there any truth to this. My friend has a dmax, is pretty healthy as far as performance mods goes, the new tune he has actually smokes less and is much faster and makes more power then the previous tune. Sorry to jack the thread.

Thanks John

 

I agree it seems like though the excess fuel may make more power it still doesn't compare to a complete, clean cumbustion with more boost.