Engine Dehumidifiers - Black Max?

Half Fast

Half Fast

Touchdown! Greaser!
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Half Fast
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I'm considering buying a dehumidifier for my engine and I'm interested in the Black Max ( https://flyingsafer.com/2065 ). I like the approach of using a thermoelectric cooler instead of dessicant, because here in Florida I think I'd be replacing dessicant fairly often and I'd like to know my engine will stay dry if I'm out of town for a few weeks.

Anybody have experience with the Black Max? Opinions?
 
I researched dehumidifiers last year. I decided to purchase a DryBot. It uses a desiccant that is automatically regenerated periodically. I have had it in continuous duty since December and it works fine. I found a few bad reviews of failures of the Black Max unit....however, there are not a great number of reviews of either unit and bad news travels faster and further than good news. An automated unit sure beats having to bake desiccant periodically. Our humidity levels are likely similar as I am located in coastal Louisiana and my friends that have 'manual' units have to regenerated the silica gel every 4-6 weeks most of the year.
 
For a few weeks? I’d do nothing. For all winter? I built my own using desiccant and aquarium pumps. Now I follow Lycoming instructions and add Cortec to my oil for storage. Welcome to the 21st century.
 
Stewartb said:
For a few weeks? I’d do nothing. For all winter? I built my own using desiccant and aquarium pumps. Now I follow Lycoming instructions and add Cortec to my oil for storage. Welcome to the 21st century.
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I fly all winter, and humidity is low then. Summer is the issue, when humidity is 95% and I might be out of town for a few weeks.
 
I contend that crankcase humidity with foul shutdown vapors is a substantial factor. Getting the bad stuff out of the crankcase becomes a lot more difficult when it already has condensed on the walls of a cooling engine and mixes with the oil in the sump. Maybe a post operation oil circulating system exposing the sump oil to a strong vacuum to boil off contaminants?

A lot probably depends on the time since previous flight and the immediate pre and post-start operation of an engine too.
 
Change oil at 25 hour intervals. Use a corrosion package oil or add one. A few weeks shouldn’t be a problem, especially if the hangar has consistent temperature control.
 
Stewartb said:
Change oil at 25 hour intervals. Use a corrosion package oil or add one. A few weeks shouldn’t be a problem, especially if the hangar has consistent temperature control.
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The hangar doesn't have any sort of temperature control, or even insulation. Summer temps reach 110F inside the hangar. Typical semi-tropical Florida.
 
What I meant is condensation is the problem. That only happens with temp changes. For your purposes just moving air through the engine would prevent condensation. Put a positive pressure air source on the breather tube or into the oil filler.
 
FWIW - My chem prof maintained reaction rates double about every 18 degF increase in temperature.
 
Half Fast said:
because here in Florida I think I'd be replacing dessicant fairly often
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15 to 18 years ago, or around about that, we bought a pop-up tent camper. I was worried about the tent getting moldy while it was folded up and parked in my yard, so I bought some damp-rid. I put some in and closed it up. I figured that there'd be some excessive humidity in the thing initially, but that once it was closed up "tight" it would settle out with a reduced humidity level inside.
Didn't take me long to realize that it was like trying to drain the Atlantic Ocean with a 5-gallon bucket! The daily heating and cooling cycle probably sucked in gallons of water in vapor form every day!

So yeah, I'm with you on the desiccant thing...unless maybe it's in something that would sense and regenerate it regularly
 
I'm using this one: http://www.rbaviation.com/mojave/ Super cheap and seems to work. It constantly shows between 10% and 20% humidity. After flight, when I plug it in it shows much higher values so the indicator definitely works. I change desiccants once a month. Sometimes I dry them at home in the oven but once I dropped them and boy was that a mess so I kinda went to just dumping them buying new ones once a month.
 
Half Fast said:
I'm considering buying a dehumidifier for my engine and I'm interested in the Black Max ( https://flyingsafer.com/2065 ). I like the approach of using a thermoelectric cooler instead of dessicant, because here in Florida I think I'd be replacing dessicant fairly often and I'd like to know my engine will stay dry if I'm out of town for a few weeks.

Anybody have experience with the Black Max? Opinions?
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I have been thinking about this issue for at least a decade, and continually engineering and re-engineering what I would build...

And then the DryBot came out, and it's pretty dang close. If you're in the market, I'd put that at the top of your list. It does use dessicant, but it automatically regenerates it so you don't need to worry about it.
 
Half Fast said:
I'm considering buying a dehumidifier for my engine and I'm interested in the Black Max ( https://flyingsafer.com/2065 ). I like the approach of using a thermoelectric cooler instead of dessicant, because here in Florida I think I'd be replacing dessicant fairly often and I'd like to know my engine will stay dry if I'm out of town for a few weeks.

Anybody have experience with the Black Max? Opinions?
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I ran a dehumidifier in my Velocity. I only had to change dessicant about once a month at the most even in the summer. I had enough to fill the container four times so when I stock ran low, I brought used dessicant home and put it in the slow cooker for a few hours to dry it out.
 
Eric Pauley said:
Can't speak to this specific product, but for that price I'd have expected a proper compressor.

Related overview of the weaknesses of thermoelectric cooling in another setting:

Has anyone tried just rigging up a conventional dehimidifer? Something like this comes to mind: https://moiswell.com/collections/du...or-crawlspace-basement-moiswell-defender-m145
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32 minutes to tell me absolutely nothing new. Edit: That said, if you know nothing about refrigeration or dehumidification it is an OK video. Tl;Dr: Peltier Junctions use a lot of energy and do just an OK job of cooling. Compressor refrigeration is much more efficient. There are specific use cases where they can work. End edit.

Hook it up to a solar panel and dehumidify when there is sun available. Works great for those of us stuck on the ramp.
I use a small panel to keep my battery topped up.
Another panel to run a dehumidifier is not a big deal. The biggest issue I have is that I want to run a dehumidifier IN the cabin of the plane, and I want to let the water drain continuously so that I don't have to stop by & drain it myself. That means I have to find a way to run a hose outside of the cabin.
 
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nrpetersen said:
I contend that crankcase humidity with foul shutdown vapors is a substantial factor. Getting the bad stuff out of the crankcase becomes a lot more difficult when it already has condensed on the walls of a cooling engine and mixes with the oil in the sump.
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I open the oil filler (Continental) after shutdown.

A nice plume of steam comes out.
 
Threads about Black Max on other forums. Some love them, others have had issues.
 
I’ve had to send my BlackMax for repair twice, and each time I think it was due to an electrical surge during thunderstorms.

Over 8 years of ownership in Florida, I’ve trended my oil analyses enough that I am confident that the BlackMax makes a significant difference.
 
So... a bit of a tangential approach or two, but how about this:

1. Remove oil dipstick and pump warm (150F or so) air into the engine. You can use the exhaust of a dehumidifier if you want that air extra dry, but I don't think it would be required.
2. Blow warm air (150F) all over the engine compartment. Keeping the thing warm will prevent condensation.
3. All of the above.
 
Well, the Mojave dehumidifier arrived Friday afternoon. I connected it up to the plane after my flight this morning, so I guess I'll see how well it works. After about 15-20 minutes of closed-circuit operation, the hygrometer was reading 10% (its lowest reading), so that's encouraging.

The bottom of my breather tube has been flattened a bit which prevented the Mojave plug from sealing very well. I wrapped a little aluminum tape around the connection and that seems to have sealed things up well enough.

The plane's going to sit for a couple of weeks while we're out of town, so I'm counting on the Mojave to provide a little insurance for my fresh engine.
 
Last time I bought a BlackMax, it was $600, more now.
Now for about the last ten years, I use a $130 Dorm Fridge with a small freezer section, and a $35 aquarium pump. The fridge holds all the cold beverages I need, and the engine loves the 10-15%RH air it gets in relative abundance.
Engine blows down from hot and 100%RH to 10-15%RH in about 20 minutes.
 
Ted K said:
Last time I bought a BlackMax, it was $600, more now.
Now for about the last ten years, I use a $130 Dorm Fridge with a small freezer section, and a $35 aquarium pump. The fridge holds all the cold beverages I need, and the engine loves the 10-15%RH air it gets in relative abundance.
Engine blows down from hot and 100%RH to 10-15%RH in about 20 minutes.
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I'm having some difficulty imagining this. Can you explain the set up a bit more?
 
Initial Fix said:
Me too …. How is this removing the moisture instead of just cooling the air?
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Cold air has less moisure in it, that's the "conditioning" part in air conditioning.
Pump that air in a warm, humid engine, and it will warm up, absorbing more moisture in the process.
 
AV8R_87 said:
Cold air has less moisure in it, that's the "conditioning" part in air conditioning.
Pump that air in a warm, humid engine, and it will warm up, absorbing more moisture in the process.
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True! The air in the 5F freezer is desert dry. It sheds its moisture to the saturation capacity of 5F air which is nearly nothing although the RH of it is approx 50%. The now dry air warms in the pump and in the hit engine where its RH measures about 10 exiting the hose. At this point it is warm exceptionally dry air ready to absorb any water it can, so its RH goes up at first. I measured 95%RH coming out of the breather for the first few moments. But by time 20 m, it had lowered to 15% RH. The fridge and pump provide a nearly bottomless supply of dry air at just a slight (blow on your hand) over pressure that pushes out the the crankcase breather and the cylinder valves.

There is one downside at the Fridge. These dorm fridges are generally not self defrosting so the have to be turned off about once a quarter for freezer section to defrost.

Ted
 
AV8R_87 said:
Cold air has less moisure in it, that's the "conditioning" part in air conditioning.
Pump that air in a warm, humid engine, and it will warm up, absorbing more moisture in the process.
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Ah no. A refrigerator (the OPs situation) only cools air it doesn’t remove the moisture.
 
I’ve used a DryBot for the past year and a half. And I’ve always used camguard. Never had an issue with the unit and my numbers did improve in the oil analysis. Love not having to do anything other than to pop it in place on the oil filler tube after flying.
 
Initial Fix said:
Ah no. A refrigerator (the OPs situation) only cools air it doesn’t remove the moisture.
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The amount of water that air can hold is reduced as the air gets colder. Cool the air enough and water is condensed out. There is no way to prevent it. That's why you have to defrost refrigerators unless you have a "frost free" refrigerator with a built in defrost cycle (the water ends up in a tray at the bottom and gets evaporated back into your kitchen.


Remember this chart?
1757878446334.jpeg

As you cool the air, you move left until you hit the 100% RH line. Then you move diagonally down as water condenses. Then when you warm up, you move straight to the right.

Assume we start at 70 F and a dew point of 50 F which gives us a R.H. on the order of 50%. Cool down to 50F and we hit the diagonal line at 100% R.H. Cool down to 20F - you will still be at 100% R.H. but would have condensed out a bunch of water and the absolute humidity will have dropped significantly. So your dew point is now 20 F. Slide to the right back to your 70 F ambient temperature and now your relative humidity has dropped to 15ish percent.
 
But the condensation needs to go somewhere. That's why an AC has a drain for the condensate. A diagram of what @Ted K is doing would help.
 
Hang 4 said:
But the condensation needs to go somewhere
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On the freezer coils, as frost.
AvNavCom said:
How is stuff hooked up, exactly?
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IF I understand it right, you make very cold (and dry) air in the freezer. Use the aquarium pump to move cold/dry air from freezer into the engine via oil filler tube. Warm/moist air comes out of the engine via breather.
 
AV8R_87 said:
On the freezer coils, as frost.

IF I understand it right, you make very cold (and dry) air in the freezer. Use the aquarium pump to move cold/dry air from freezer into the engine via oil filler tube. Warm/moist air comes out of the engine via breather.
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Okay, so if I understand correctly, we're drilling a hole through the refrigerator wall to run one end of the pipe into it, hooking up a pump to drive airflow outward, and the other end of the pipe goes into the oil filler tube, with the air ultimately exhausted via the breather tube. Presumably there needs to be some sort of intake pipe too, as refrigerators are fairly airtight last I checked. Interesting.
 
AvNavCom said:
Okay, so if I understand correctly, we're drilling a hole through the refrigerator wall to run one end of the pipe into it, hooking up a pump to drive airflow outward, and the other end of the pipe goes into the oil filler tube, with the air ultimately exhausted via the breather tube. Presumably there needs to be some sort of intake pipe too, as refrigerators are fairly airtight last I checked. Interesting.
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The intake hose going to the pump from the inside of the freezer section, runs thru a larger stiffer hose to pass thru the fridge door seal. This allows the intake hose to keep from getting crimped shut in the door seal, and allows a path for air to enter the freezer section to replace that which is pumped out.

And yes, the freezer section frosts up as that warmer air cools dumping the moisture it was carrying. I have to unplug the fridge and let it defrost about every three months.

Ted K
 
I wonder about keeping a big cylinder of nitrogen in the hangar. Run it into the oil filler tube flow a good bit to flush out the moist air, then either shut it off or leave it on a really slow feed.
 
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