Generator wet stacking discussion

[Dwnorton1]

A few fellow SS members and I were talking about generator sizing, which ended up in discussion about wet stacking by not keeping enough load on gen to keep exhaust valve hot enough to keep sludge from building up.

My question for the group is would it be feasible or even make a difference if you were to swap out thermostat with a higher range to keep engine temps up higher at lower loads? My 802 runs about 180 degrees at full load give or take.

I know the best thing is to size gen to load but the 802's 5kw is best small unit, the 831 on market now might be better sized for a lot of applications, but are flakey and I believe will have inverter failure at some point as the capacitors age, just nature of beast. In my industry we change out caps at about 5-7 years due to failure rates. That being said using 802 to run RV only loads to about 30%, so hence this discussion.

Thoughts?

 

[csheath]

It might help. Remember to increase radiator cap pressure as you increase thermostat temperature.

 

[snowtrac nome]

It might help. Remember to increase radiator cap pressure as you increase thermostat temperature.

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.

 

[jamawieb]

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.

 

[Dwnorton1]

We had same discussion about adding a heater out at unit to add load to to keep temperatures up, was just exploring options. I had not thought about exhaust system adding to problem, but definitely makes sense. I posted because I figured if the thought had occurred to me then someone else had tried.
Fuel consumption will be about same regardless of load, at least until getting close to full load correct?

 

[98G]

The thought occurs to me to run the RV from a battery bank, and feed the battery bank from the genset.

Allow the battery bank to become somewhat depleted before starting the genset, then run the genset high enough to prevent wetstacking.

Since this seems obvious to me, I must be missing something. What am I missing?

 

[jamawieb]

The thought occurs to me to run the RV from a battery bank, and feed the battery bank from the genset.

Allow the battery bank to become somewhat depleted before starting the genset, then run the genset high enough to prevent wetstacking.

Since this seems obvious to me, I must be missing something. What am I missing?

Seems logical, most inverters will pull huge amperage at first to quickly recharge the batteries.

 

[Dwnorton1]

You would have to have really big charger to put enough load on gen would be problem.

 

[Dwnorton1]

Another question. How long duration of a run before it becomes a problem? If it takes a while to become a problem, then you could manage by really loading up periodically to clean up? If it happens quickly then just adding load to get to that sweet spot of 60% would be simplest solution.

 

[DieselAddict]

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.

 

[98G]

Another question. How long duration of a run before it becomes a problem? If it takes a while to become a problem, then you could manage by really loading up periodically to clean up? If it happens quickly then just adding load to get to that sweet spot of 60% would be simplest solution.

My reading suggests that it becomes a problem fairly fast (a few hours?), but that periodically loading it will clean it out.

http://m.csemag.com/index.php?id=95...=36382&cHash=e0b399904af236d9f863742ca8f03440

 

[Daybreak]

Howdy,
You say it runs at 180 degrees now. In the middle of summer, or ambient temp 80 or higher, it will be around 200.

Wet stacking is not so much a temperature issue. The simple method of a 1800rpm engine without advanced fuel delivery. Because the fuel delivery is simplistic, a load considered to be...er.. its listed somewhere, like 60% or higher will make a more complete fuel burn. 50% or less can lead to wet stacking

Wet stacking is caused by unburned fuel. The combustion process is not complete. That is also why it can be cleaned up with a good hard load. Diesel engines like to work.

MEP-8xx wet stack info

working some TQG on a load bank. I also made some logs with temps and conditions

Acquired a Military surplus load bank

 

[rustystud]

My reading suggests that it becomes a problem fairly fast (a few hours?), but that periodically loading it will clean it out.

http://m.csemag.com/index.php?id=95...=36382&cHash=e0b399904af236d9f863742ca8f03440

Your correct. Wet stacking can happen in hours if the unit is over fueled. Remember wet stacking is not about the heat of the engine, but the heat in the chamber. Which only happens under load. So it's all about the load and unburned fuel. It's the unburned fuel which causes all the problems, like washing out the cylinders and creating extreme wear on the liners. Then there is the whole bearing thing with all that fuel getting into the crankcase. With all stationary mechanical injection engines, the pump is injecting the same amount of fuel whether it's running at max load or not. There's no throttle. When it's running at a light load most of the fuel is not getting burned and it builds up in the exhaust and washes down the sides of the pistons.

 

[Dwnorton1]

Thanks for the input. I wasn't sure if it was more of just a risk of muffler/exhaust fire or if engine damage was plausible. I had seen pics of one at auction a while back that had slobbered around manifold gasket until whole side of motor was covered in gunk and the area around flapper was severely sooted up. Unit went really cheap, I didn't know if it was just something that could be cleaned up or if severe damage had been done.
I really do appreciate the experience from you guys that have been into this for a while helping us who are still trying to learn. Great forum.

 

[Chief_919]

While running at load will "clean up" the evidence of wet stacking, it won't undo that damage that was done to the cylinder rings and walls while the wet stacking was happening, nor will it get the unburned fuel out of the oil that will become diluted.

So its is kind of a misnomer to say running it at load later will "clean up" or "clear up" the wet stacking. It will clean away the evidence of it, but it won't undo the damage.

 

[csheath]

Sounds like in addition to monitoring excess load I will need to keep my clothes dryer running at times of minimal load if I get a long term outage. I guess I will spend a lot of time doing load management when an outage occurs. Not something my wife could do if I wasn't here. It will still be nice to have the power to run things like well, water heater, and AC when it's needed. I'm thinking I should shoot for at least 30 amps constant on my 803. I don't know what the starting amps is on my AC unit yet but I can test that now that i have a clamp meter with a max hold function. Seems like I tested the start amps on my well and it was pretty high but I didn't record the info. I do know when I tested my AC unit the generator gave a grunt that lasted no more than a second and it was purring away with an extra 12 amp load when I checked it.

My unit has had very little to no smoke so I'm assuming it was at least run at enough load before I got it to clean it up if it ever got wet stacked. It has a faint hint of smoke at start up but clears within seconds.

 

[Daybreak]

Howdy,

To explain a little more about wet stacking. Because a engine wet stacks does NOT mean it is damaged. It depends on how long you keep going under those conditions. To put out a blanket statement like that is not true. You need to physically change the oil of course. The oil will not make itself better. The same thing can be said about water getting into the exhaust. If water got in the exhaust and you drained and changed the oil 2 days later, do you think it was major damage compared to some units sitting for years in that condition? Wet stacking can lead to catastrophic engine failure. shoot, running your unit with no oil it can do that too. A lot will depend how long the unit runs in the condition. Will a unit shows signs of wet stacking after 8 hours? Maybe not from the outside, but, for the engine (rings and oil) to clean up the system before it does permanent damage. Cylinder walls get varnished, glazed, rings have more bypass, fuel gets in the oil, exhaust passages gets clogged. Known as slobber. Can show like thick molasses running from fittings and gaskets. Things then start to snowball and can lead to permanent engine damage.

 

[Dwnorton1]

Well my philosophy from now on is to simply have a little heater or some other extra load when supplying load to whatever that doesn't keep load up in proper load range for the gen set I am using. Seems to be simplest solution, especially when running a RV who's load is only 30% when A/C compressor is on and less when between cycles.

Ounce of prevention is worth a pound of cure.

Will still buy one that shows signs of this issue, mainly because I am a cheapskate and willing to roll dice if price is right, worst outcome would be I have a parts unit.

Thanks again for the education.

 

[DieselAddict]

If this is something that truly worries then the best thing to do is to install a EGT with a data recorder. If you accumulate too many hours of light load as will be shown on the EGT then run your dryer for an hour.

The second thing you can do to minimize accumulation is to insulate the exhaust manifold with ceramic wrap. Insulate everything in the exhaust path to keep the temps as high as possible. Avoid extending the exhaust and if you do have to extend it don't make it huge. That will just cool off the gases and exacerbate the problem.

 

[flydude92]

So how much different is the genset engine compared to a diesel in a truck especially those that make short local trips? People put cardboard in front of the radiator to increase
the engine temperature. Is that more to increase the heat in the truck or to help the engine a little. Granted it doesn't help the exhaust gas temperatures but I would
think having the engine run at proper temperatures would help keep the valves (maybe), rings, etc seated properly.

I am referring to this SS thread: http://www.steelsoldiers.com/showthread.php?162826-M1008-Not-Reaching-Running-Temp