I've been a diesel and steam engine mechanic for 25 years now and never heard that term till I started working on powerstrokes. I still never figured out exactly what it is though.

 

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Wet stacking is a condition in diesel engines in which all the fuel is not burned and passes on into the exhaust side of the turbocharger and on into the exhaust system. In Diesel generators, it is usually because the diesel is running at only a small percentage of its capacity.

It is detectable when there is a black ooze around exhaust pipe connections and around the turbocharger. Continuous black exhaust from the stack when under a constant load is also an indication that all the fuel is not being burned - good preventive maintenance is critical for this type of generator application.

lol i also wanted to know so i googled it for ya.
Mitch

 

So what does this hurt then?

On a steam engine, well boiler, unburned fuel going up the stack is a really bad thing. It's usually in the form of white smoke. I've seen people die from it before when the boiler and stacks exploded. Seen it happen twice now.
I can't imagine it happening on a truck. So why is it suck a big concern?

I know most of you are like me in that you would rather be burning that fuel and getting something from it but that can't be all there is to it. I can't imagine it's good for the cats at all though.

 

Thanks for the info.
I wonder how much extra fuel is required to wet stack.

 

we refer to it in the military vehicles as well, but a little different, they consider it wetstacking when the trucks idle too long and unburnt fuel begins to build up and wash the rings out. its a problem on some of our vehicles because they are running higher hp numbers and have the fuel "turned up" on them. the fix was to have teh trucks run at a high idle if idling for more then 2 minutes

 

From what I remember off the top of my noggin, wet stacking is caused by excessive idling with low EGT's. The concern isn't unburned fuel out the tail pipe (who gives 2 craps about that honestly... most of us try to get our trucks to dump black smoke) but rather that if the motor wet stacks enough, it will wash down the cylinder walls (decreasing lubriction of the cylinder) and cause build-up on the piston crown, valves, etc. I also remember reading that thanks to the fancy electronic gizmos bolted all over the hunk of iron under the hood on our trucks, wet stacking is a non-issue.

On edit- c00n replied while I was typing my response.

 

hahahaha, beat you to it. lol

 

So it is not a concern for us? That would be great if it wasn't.

 

I don't know. Computers can only do so much. As cold as we've been lately I can't start any of my diesels, except the new tractor, without smoking white. My kids IDI will smoke for an hour if he doesn't start using it hard right away. Mine PS will smoke all day long idling. It goes away after the first time I give it some gas and doesn't come back till it cools off overnight again.

I can't imagine diesel hurting the rings much though. I worked on two strokes too much to know better than that. Those things inhale liquid fuel when they are cold and spit out fire half the time. Especially the BIG ones. We haven't warmed up the fuel on Navy ships, for boilers and diesels anyway, since the conversion from black oil to Diesel on everything.
It is pretty cool seeing fire belching out of an opposed piston 16 cylinder engine that is so big you can stand inside the cylinder. Imagine one of those old things in our trucks!!!

 

pretty sure its not good for ours, especially modded. i know there was tsb's a while back regarding plow trucks and buses with 7.3's in them but i would have to dig to find them. it had to do with adding an auxilery pcm for extended idle times to prevent engine damage. i dont recall them saying what the concern was but i would be willing to bet it had to do with wetstacking

 

I have only seen wet stacking on generators. I believe it is caused by running at a low %. When it runs low the exhaust doesn't get hot enough burn the unburned fuel. The fix for the generators is hook a load bank to it and pull 110% load and go to lunch for an hour. You can tell it is wet stacked b/c the 2" exhaust pipe will have caked on crud and the hole will only be 1" or so.
I run the crap out of my vehicle so I never even thought of wet stacking.

 

I wanted to get a AIC for mine but as luck would have it I can't find one of those now either. I idle the truck a lot. And the tractor. At least the tractor has a hand throttle though that I can turn up the speed with. It's even got auto pilot. Seriously.

I do agree that it's a good thing to turn up the idle speed on a diesel if you are gonna sit a while. Big ones will shake themselves apart if you don't and I guess it's bad for the rings on these. I got a feeling with my new clutch that idling will be a little noisy too if I don't find a way to increase the speed.

 

The AIC's pop up on Ebay from time to time, but they usually run at least $100. I got mine for a bottle of whiskey from a guy I know off another forum
FWIW, I've heard that when idling you should have temps of at least 300°. To get above that in my pile of crap, I have to set the AIC to jump start mode, which is like 1749 rpm or something like that. With my 1200rpm high idle tune it only gets about 250° on the EGT gauge.

 

What does the term "Wet Stacking" mean in a diesel engine? - Diesel Generator Set

What does the term "Wet Stacking" mean in a diesel engine?

"Wet Stacking" happen when a diesel engine operates below the rated output level the engine starts over-fuel or "wet stack". Diesel engines are designed to operate with a load and operate more efficiently in the 70 to 80% range of rated output. When a diesel engine operates for a long period of time below 40% it begins to over fuel. This happens because the injection tips begins to carbonize and disrupt the fuel spray pattern.

 

Ranch- it just so appens that i was on fleabay last night and i saw two of those idle controllers going for a fair price