Generator wet stacking discussion

[lindsey97]

I was a 52d wet stacking is caused by incomplete combustion raising the t stat temp wont help a lot. the other problem is the tqg series gen sets had a highly restrictive exhaust muffler which added to the problems caused by wet stacking your generator will run at max efficiency at 60 percent load. my suggestion would be to create a variable load bank a simple way to do this would be with an electric heater and depending on the load you have you can selectively turn on coils in the heater. I would not restrict cooling as you will still have still have the same fuel charge that isn't burning all the way across the top of the piston.

What about some custom porting/polish work on the head? Or checking/setting the squish on the head/piston? Do diesel have squish like a 2 stroke engine? What about custom injectors with a smaller/different spray pattern and or changing the number of spray ports on the injector tips?

 

[lindsey97]

Sorry to be the bearer of bad news but it won't work in the summer months. If you increase the thermostat to 190+ on hot days, the unit just gets to hot and the unit shuts down. The temp the unit shuts down at is 225 and when the thermostat opens at 190 or above, it just doesn't have enough time to cool. I've tried this in the past to keep a unit from wet stacking. FYI the thermostat's are standard Chevrolet thermostats.

Which chevy thermostat? Old small block chevy 350? If the stock thermostat on a MEP-802a is a 170 degree, then maybe a 180 deg. F would be worth trying, depending on your operating environment.

If you guys really want to "experiment" with raising the operating temp of the coolant, and do it on the cheap, then all you need is duct tape(green or tan), and a sheet of cardboard or similar material. Block off the exit side of the radiator, on top of the MEP, start with 25% reduction and then move up. YMMV. A good IR thermal gun will be helpful, and record your ambient temp while experimenting.

We add cardboard to our dump trucks in the winter, in front of the radiator, in order to increase coolant temperature, and promote opening of the thermostat, which in turn keeps my butt in the cab warm.

 

[Another Ahab]

Which chevy thermostat? Old small block chevy 350? If the stock thermostat on a MEP-802a is a 170 degree, then maybe a 180 deg. F would be worth trying, depending on your operating environment.

If you guys really want to "experiment" with raising the operating temp of the coolant, and do it on the cheap, then all you need is duct tape(green or tan), and a sheet of cardboard or similar material. Block off the exit side of the radiator, on top of the MEP, start with 25% reduction and then move up. YMMV. A good IR thermal gun will be helpful, and record your ambient temp while experimenting.

I might be missing something obvious, but how is the color important for this?

 

[Dwnorton1]

We were actually talking about 6 elements of various voltages ant wattages to test up to about 20000watts in a 35 gallon propane tank with a radiator and small circulation pump and fan. Could serve purpose of load bank and emergency hot water if needed. Yes with a PRV.

 

[Dwnorton1]

I might be missing something obvious, but how is the color important for this?

Because the other colors would clash of course. Lol

 

[lindsey97]

Dieseladdict nailed it in post #38.



Matching paint is standard protocol for redneck testing at my base of operation.

 

[m16ty]

It takes many hours of running under 25% to cause the problem and only an hour or two running at 75% to clean it up.

Dont worry about it.

I agree with this. I tend to think people worry way too much about wet stacking.

I know we've ran farm tractors for days on end pulling small loads without damage. Most OTR tractor trailers run all night just keeping the A/C or heat going, again, without damage.

 

[rustystud]

I agree with this. I tend to think people worry way too much about wet stacking.

I know we've ran farm tractors for days on end pulling small loads without damage. Most OTR tractor trailers run all night just keeping the A/C or heat going, again, without damage.

Farm tractors and over the road trucks all have throttles. When their idling, the throttle is barely open unlike a fixed RPM machine like a generator which is set to run at the desired RPM (like 900 RPM or 1800 RPM or 3600 RPM) . It's the "fixed" throttle position and the maintained RPM level that is the problem.
When the power goes out here, it can last for days. My MEP-002a will wet stack after 12 to 14 hours of under 25% load. So I turn on all the lights and even my A/C unit (in summer) to keep the load up.

 

[justacitizen]

whew what a thread!! My opinion is if the Generator is sized correct for your load and lifestyle in this case,wet stacking won't be a problem. i have run my farm on an MEP 002a during outages from a few hours to a over a month continuous. never ever had to worry about wet stacking. now if i had a 15K it might be a problem. with the 002a most of the time just running a few lights a tv or something and then POW the well kicks in or the wife runs the dryer for 30 min or so. it just doesn't seem to be a problem if your load and generator are correct.

 

[Guyfang]

Here are my thoughts on wetstacking.. Strictly my opinions based on a reasonable amount of experience running/fixing MEPs and being system owner of 2MW of diesel generators at work for more than 15yrs.

Without a doubt if you idle your generator for long periods you are going to cause problems. It is basic physics. Diesel engines are very heat efficient and without load they don't make a lot of it (heat). Low heat means incomplete combustion. Low heat in the presence of condensable gases (unburned fuel and water vapor) is a recipe for bad things to happen.

There are conditions that will make this worse. Bad injectors, incorrect timing, low cylinder compression, **** even a partially clogged air filter are all things that will make the engine not burn fuel efficiently which will increase wetstacking potential. My point here is that a correctly running engine with good fuel delivery will not wetstack as quickly as one with problems. This is why (in my opinion) everyone should KNOW the condition of their set. One of the best ways to get a lot of info with low effort is oil analysis. You'll want to do more than one on a single oil change. You need at least 25 hours for the first sample and at least 50 hours on the second. Look for trends in your fuel accumulation. If you are quickly accumulating fuel, your set has an issue that will increase your wetstacking potential. If your fuel accumulation is low your wetstacking potential is lower.

Wetstacking potential management: Knowing the condition of your set will tell you how to mange its wetstacking potential. If you have a set that accumulates fuel quickly in the oil you may have to go after some kind of constant load mechanism as is being discussed here (assuming you can't resolve the issue causing the problem). If you have a set that accumulates very little fuel in the oil you may be wasting resources in the form of extra fuel or in the cost of building an automatic dummy load. Regardless of the condition of your set you can minimize the potential of the exhaust condensing gases by simply insulating everything. You'll reduce temperatures inside the cabinet and overall do only good for the set in the long run. Why don't they already come that way? Money, Plain and simple. Insulating the exhaust will not change the cylinder conditions much. I think the issues with cylinder washing in diesel engines is not as severe as it is in gas engines.

If you have a good running set with low fuel accumulation in the oil its likely you need to do NOTHING about its wetstacking potential. And by nothing I mean nothing extraordinary. You still need to load test your set on some a basis that gives you confidence it will work when called upon. For me that means yearly. I'll accumulate between 30 and 50 hours MAX a year on my main set (weather depending). The more lengthy outages for me come in the winter (another factor that increases my wetstacking potential). Until recently my main set was a MEP-003. The base load for my house is 600w. I have to try to get it over 8kw. The vast majority of the time its under 1kw. I acknowledge that the 003 has a lower wetstacking potential due to its design versus the 80x machines, but just for conversation sake I can say that running it for hours on end with under 1kw of load on it didn't hurt it at all. I load tested the crap out of it before delivering it to my neighbor to use on his farm and I can say that it showed virtually no signs of wetstacking. It handled a 10kw being dropped on it without missing a beat. It smoked a little but it cleared up in a few short minutes to a steady light haze.


On the flip side I've bought several MEP-802s at auction that were so severely wetstacked that they wouldn't support more than 50% load without falling on their collective faces. Even the worst one I've encountered cleared up and would pull 6.5kw resistive load with less than 4 hours work. These things were smoking so badly that I was concerned they would catch fire. We are talking about really severe wetstacking on the scale I expect a member of this forum to NEVER cause in a unit under their care. To get these units cleaned up took a few gallons of diesel and some of my time. None of them have failed to run for their new owners. The one that was the worst is now at my brothers house and works great for him. I shake my head at him because he has an electric string trimmer and he runs it off the generator for fun. He adores that thing. When I load tested it in the fall it was fine.


Unless you idle your set for a couple hundred hours or you have one of the mechanical problems I mention above I really don't think you are going to encounter this condition on a scale that a 30-45 min run on a load bank doesn't clean up. If you run a load of clothes through an (electric) dryer or bake a ham while you are on generator power my money is on NEVER seeing the problem.


From a pure fun standpoint building an auto-load bank is awesome. I totally support the spirit of the endeavor. I can't wait to see what you come up with. I doubt there is a lot of need for it but its very cool.

Exactly!