EA300 temperature regulation

[thomasonw]

Question for the group:   This winter I am doing some work on my DC generator, getting it ready for next season.  One thing that has bothered me was the small Kubota EA-300 (and EA330) engines have no cooling water temperature regulation.  The Radiator and Fan sit on top of a hopper cooling the cylinder with coolant thermal cycling up and down.  There is no way to control the engine temp - though I suppose one could cover up part of the radiator blocking air flow....

In my marine deployment the radiator has been replaced with a sea water heat exchanger and the same situation:  No engine temperature regulation.  With the engine controller monitoring everything I have no worries of overheating, however, it runs cool..   Or at least cool compared to what I kind of expect.   During operation under load I see temps typically in the 140-150f range.  This is with 50-60f sea water.  To get to the 180-190f I guess I could head South, sea water around 80f or so would get close!

Given the little Kubota was apparently designed for a wide range of operating temperatures, including I have to expect running cool, I am wondering if this is an area I should put any effort into trying to 'improve'.  Adding some external bypass for the sea-water around the heat exchanger to bring the engine temp up to say 180-190f independent of sea water temp??

What ya all say -

• Wow, what a brilliant insight, and here is here is just the part you can use.         -or-
• Man, get a life.  The engine was design for this, and any 'improvement' you make will just be a wasted effort.
  

Thank you,
-al-

[joeblack5]

I think the temperature should be fairly constant at . The hopper cooling  works with evaporating water. The temperature should be only depending on the air pressure or height. Since you are at sea level I do not think it is an issue. With your setup the the water condenses again because of the cold sea water and falls back into the hopper.  The issue that would make it stop working is if you have to much water ( coolant) in the hopper so that it is in direct contact with the sea water heat exchanger. Most likely the engine would not be able to reach a proper temperature.

Good luck.
J

[glort]

There is no way to control the engine temp - though I suppose one could cover up part of the radiator blocking air flow....

Well what about exactly that?
Make up a set of shutters that are controlled by a stepper motor from a controller monitoring the engine temps.
The shutters are closed restricting airflow when the thing is cold, open when it's hot.

Alternatively just use an automotive type electric cooling fan controlled by a temp sensor.

And before anyone chimes in about electric fans failing or being unreliable....
My old man threw out a heap a few months ago because the only time he sells the things are when they get damaged in accidents.  I picked up 8 of them because I couldn't  help myself.
Actually I thought of a few things like setting some up under the back verandah for a bogan created breeze in summer.

In a bored moment I set one up under the awning and powered it up with a battery charger. The thing has been there running 24/7 for 34 days so far. The thing was off a 2004 model vehicle and has done all that work before I got it.  Seems to me these things, at least the ones on Subaru's  ( Mitsuba brand) are Bloody reliable and long lived.
I have also put one in the window of a spare room on the cool side of the house and have been running up some hours on that as well.

Seems to me the problem with insulated houses are on hot days when the temp drops at night, the insulation works well at keeping the place too hot.  The outside air can easily be 10 or more degrees cooler and bringing that in makes a big difference to the need of effectiveness of the AC.

In any case, these used automotive fans are so cheap you could afford to have a dozen spares and in doing that you'd be passing them on to your great, great grandchildren I expect.

[BruceM]

Joeblack5 has a good point.  The small hopper regulates the temperature at the boiling point.  The radiator/fan is just a condenser. Simple and reliable.  Unless I'm misunderstanding the setup it is already temperature regulated.

[Henry W]

These engines do run cool in cooler weather. The problem here is this engine temperature will change with outside temperature and it is hard to regulate without a thermostat setup. I will be setting up a thermostat setup with a pump in the future. Be careful not to run to much antifreeze in hot weather. A 50% mixture will cause overheating in hot weather unless the cooling system is modified like a modern automotive setup. In hot weather it is best to run straight water with an anti corrosive additive.

Henry

[thomasonw]

Thank you everyone for replying, and I can see I did not describe the current setup well enough...

As shipped, these small Kubota engines have a radiator on them, with a belt driven fan.  There is a pressure cap, but no internal thermostat - the temperature is what it is.  Here is a photo of the engine when I 1st was installing it, and while it still had its radiator:




However I have sense modified it.  Replacing the radiator with a marine heat exchanger that takes in sea water and uses that for cooling, here you can see a photo with the heat exchanger:




Still there is no temperature control - the heat exchanger sits on top of the cylinder, just as the radiator did, and coolant thermosyphons around the cylinder and up to the heat exchanger...


If I still had the radiator I would likely install a small 12v fan and put that on a thermal switch, just like many automobiles are today.  But with the sea-water heat exchanger, about the only option I can think of is to install some type of bypass valve in the sea-water hoses to and from the heat exchanger.  (I need to keep the overall flow of sea water up, as it is also used to cool the exhaust, and as a pre-feed for our water maker).   So, I am wondering if I need to take the steps to install the bypass (and if so, what I might use - if anyone has a pointer!), or if just leave it as is.

Perhaps the two things that are struggling in my mind (Ok, not just these two  ) are:
1) The motor is running cool, I measure around 140-150f, depending on the temperature of the sea water
2) The original design had no thermostat, so perhaps running cool is not really an issue for this guy...


If #2 is true (in that is is not a problem for these little guys to run cool)  then perhaps I can set aside this mind-struggle and move on to others.  But if indeed running at 140-150f is just looking for trouble down the road. . . . .

Appreciate your help and thoughts, and sorry I did not accurately describe things in my 1st posting.

-al-

[thomasonw]

These engines do run cool in cooler weather. The problem here is this engine temperature will change with outside temperature and it is hard to regulate without a thermostat setup. I will be setting up a thermostat setup with a pump in the future. Be careful not to run to much antifreeze in hot weather. A 50% mixture will cause overheating in hot weather unless the cooling system is modified like a modern automotive setup. In hot weather it is best to run straight water with an anti corrosive additive.

Henry

Thanks, I am looking to change to a non-toxic antifreeze, as we actually use the heat from this engine to pre-heat sea-water before sending it to the RO water-maker.  The RO system works better with warmer water.   (He, I guess I am doing a sort of co-gen after all!)   Interested in how you are thinking to modify your engine cooling, will you retain the radiator?  Or are you going with something off-engine and a small pump in between? or??

-al-

[glort]

What about tapping off the mai feed line and instead of having a radiator fan, have an electric pump. When the engine is hot, the pump kicks in and circulates in cool water till the temp drops back down where you want the min temp to be.  I think the only thing you would need to do is is have an electric pump instead of an electric fan.

[mobile_bob]

unless someone has already mentioned this,  it will be a +1

just get a fan temp switch, that way it kicks on at about 200 degree's and cuts out at about 190 or so

then no matter the ambient or load, the engine will have to get up to 190 before the fan kicks on and cools the engine.

i believe your engine is a captive system, with radiator cap?

that is what i would do, that is if i were to want to keep the oem fan/radiator system.

bob g