Diesels loading up?

[The motor guy]

I've asked this question several times in various forums, and I've never gotten an answer. When a diesel is lightly loaded for a while and suddenly it receives a large load, where does all the black smoke come from? It's my understanding that it's just buildup inside the exhaust and the extra flow of air is just blowing it out, so it's not really from the engine itself.

 

[97prizm]

I've asked this question several times in various forums, and I've never gotten an answer. When a diesel is lightly loaded for a while and suddenly it receives a large load, where does all the black smoke come from? It's my understanding that it's just buildup inside the exhaust and the extra flow of air is just blowing it out, so it's not really from the engine itself.

The system is adding fuel so it doesn't go lean and burn a piston or that the engine is overfueling or not burning off excess fuel.

 

[The motor guy]

The system is adding fuel so it doesn't go lean and burn a piston or that the engine is overfueling or not burning off excess fuel.

I disagree because it would do that all the time, everytime. Usually it's like a once every 100 mile type of thing

 

[supton]

That's my take too. That soot is coming out but at low speed, falls out of suspension, and just builds up in the nooks and crannies. Give it the beans, blow lots of air through the system at high speed, and you just see "lots" of soot--but it's really all the soot that wasn't coming out before. It didn't make any more than when you are on it all the time, it's just an accumulation over time.

 

[97prizm]

I disagree because it would do that all the time, everytime. Usually it's like a once every 100 mile type of thing

Could be a bad regen cycle.

 

[Chris142]

It's blowing carbon out of the exhaust

 

[The motor guy]

It's blowing carbon out of the exhaust

That built up over time?

 

[Chris142]

That built up over time?

Ya. If I putt my truck around town for a day or 2 then stomp on it the smoke will be outrageous for a few seconds. If I stomp on it often there's never a huge cloud.

 

[The motor guy]

Ya. If I putt my truck around town for a day or 2 then stomp on it the smoke will be outrageous for a few seconds. If I stomp on it often there's never a huge cloud.

Same here. Well that answers it then, thanks

 

[The motor guy]

She runs smoother after too.

 

[atikovi]

Let me search that for you,

Rolling coal - Wikipedia

en.wikipedia.org

 

[dnewton3]

Black smoke is an indication of fuel which is incompletely burned. It's common (especially in IDI engines) to get this effect when the shot of fuel is greater than that which the oxygen level can sustain when tipping into the throttle. This is also common when a boosted engine sees a shot of fuel quicker than the boost can respond. It's temporary and nothing to be concerned about.

Roaling coal is just an extreme example of this phenomenon. Black smoke is always present when not enough oxygen is present.

In a diesel, you can never have too much air, but you can have too much fuel.

 

[eljefino]

The old Alco locomotives used to be good for this: Fuel now, air and power maybe later. Smoke in the interim.

 

[The motor guy]

Let me search that for you,

Rolling coal - Wikipedia

en.wikipedia.org

That's totally different than what I'm talking about. I'm talking about stock diesels that haven't been messed with.

 

[dumkid]

If a diesel is run at high rpm and low load for a long time, something called "wet stacking" can happen, where fuel builds up in the exhaust. I don't know if it happens in computer controlled diesels though.
And if you suddenly increase the load on a diesel, you have to increase the fuel and wait for the turbo to catch up to maintain the same rpm.

 

[The motor guy]

If a diesel is run at high rpm and low load for a long time, something called "wet stacking" can happen, where fuel builds up in the exhaust. I don't know if it happens in computer controlled diesels though.
And if you suddenly increase the load on a diesel, you have to increase the fuel and wait for the turbo to catch up to maintain the same rpm.

I always thought it only happened during idling speeds

 

[dumkid]

I always thought it only happened during idling speeds

It happens whenever there isn't enough load on the engine to keep the combustion chamber hot enough to completely burn the diesel. It happens in generators that are always running at about 3600 rpm, but aren't under load (only a few amps are being drawn)

 

[The motor guy]

It happens whenever there isn't enough load on the engine to keep the combustion chamber hot enough to completely burn the diesel. It happens in generators that are always running at about 3600 rpm, but aren't under load (only a few amps are being drawn)

They usually run at 1800rpm unless it's some portable Chinese pos.

 

[dumkid]

True, but there's plenty of Chinese pos generators out there and a whole lot of information on other forums about them wet stacking and smoking and missing and other fun things.

 

[The motor guy]

True, but there's plenty of Chinese pos generators out there and a whole lot of information on other forums about them wet stacking and smoking and missing and other fun things.

I always see them with glowing mufflers and sparks flying out on YouTube lol