BCM Community

   I have a 4 cylinder Kubota 15kw genset that you can see in the pictures does not have a shroud around the fan. There is however a box/shroud at the exit of the radiator that is  tightly sealed & all air is directed out the hole in the bay floor (not shown in pictures). The gen compartment is a tight box & is insulated. The radiator fan is trying to push air through the gen. I can feel air that is backwashing around the fan edges due to lack of shroud. When sitting the temp on the gen pushes 190. When driving after approx 45 mins I have to shut it down as it has reached 215. I have an air diverter/scoop that extends down 4 inches & was hoping this would push air into the compartment. Is it possible that I have a negative pressure being created as I'm driving?
     I am considering whether to make a fan shroud as I don't know what the radiator is from so I can't just go get one. I am also considering a furnace squirrel cage fan mounted at the exit side of the radiator to pull air through & since this box I built is so air tight. With that being said is there a guide as to CFM of the fan & amp draw?

I'll have to load pictures later as photobucket is screwed up this morning.

John,On my Eagle I take air in between the front tires and exhaust it out the bottom of the first bay. When I am sitting still I have no problem cooling the generator. When I am moving it will get hot and shut down. I have added a 12 volt fan at both ends of the cooling duct and it will cool except if it gets real hot, over 100. I think I have two problems one the road is always hotter thus you start with warmer air, two I think the Eagle has negative pressure under the bus when going down the road. My 15 will have a radiator mounted in the spare tire bay and will have some ram air to cool it. I will also plumb the generator cooling system into the main radiator to have two ways of cooling the generator.

Wayne

 

Had the same problem with 15 KW Kubota gen set  in my Cole converted coach. The thing had 25 hours on it when I bought it. Would shut down after about 10 or 20 minutes. Had one big blower in separate box and no fan on gen set.  Box was totally sealed and insulated where engine and gen set. Separate box and compartment with radiator was housed. Justin Griffith (a member on the board here and lives in Taylor Tx.) cut a couple more vent holes for mine so it could draw more air. He also pump installed new waterpump because mine was starting to seep. Mine had shutdown for heat and oil which before would shutdown a little over 195. Watch that heat and check and see if you have a shutdown cause it could save that high dollar engine.

PS. He also r and r'd my OTR coach air at his shop and that thing will freeze you to death.

   On another note Wayne you'll be glad to know all my black smoke issues are gone. I found out that it helps to utilize someone who knows what they're doing. Cost me twice on this one...

Photobucket still down. I'll take a couple of pics with my phone & load em up...

So much on this subject!!! I learned a TON from the members on this one.  we too had sound proof generator compartment with baffles for airflow to keep it quiet.  Problems problems problems.  We had two  fans.  One for radiator, one for air in.  BUT not enough air flow, and with an air tight box, no real way for air to properly exhaust.  Notice I said fan in & airtight.  I didn't say exhaust air OUT.  So, if you have air going in, make sure it can get out, or vv.  Make sure of your air flows.  Ours was overheating, shutting off, and we also had a problem w/ the fuel pump placement but that's another post.  Much more on this - will follow up if need specifics or pictures.  Many more on this board are more qualified than me.  Glad to help how I can tho'.  

Watch air flows!

Kind Regards, Phil

Here's what it looks like

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(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fimg.tapatalk.com%2Faefc91ab-aef6-44d4.jpg&hash=bd556c6d19772399f01c9ba92a0fd11486b80975)

(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fimg.tapatalk.com%2Faefc91ab-af18-1f6a.jpg&hash=72278f5fbaadd70852ff1bfcabef7d35b8f1d22b)

My fan set up is different than yours but I have had similar experiences.  I had no issues til I put a water heater close to the remote radiator -- then I was ok parked but overheated when driving.  To correct my issue I made a fan shroud that works well. I made the shroud itself out of four pieces of sheetmetal (26 ga) riveted on the corners. I had no attachment points on the radiator so I made brackets to hold the shroud close to the radiator. To seal the shroud to the radiator I used a stick of garage door vinyl weather strip. I positioned it so the soft vinyl part was touching the radiator and attached the rigid part to the shroud. I have not had any cooling problems except the time I got an air bubble in the coolant. The results of that are in another thread.

http://www.busconversions.com/bbs/index.php?topic=20620.0 (http://www.busconversions.com/bbs/index.php?topic=20620.0)

HTH

Melbo

The Eagle Matt bought from me has the generator in the first bay drivers side mounted length ways has a remote radiator between the drivers and passengers side inside the frame with electric fan 110v and a sound box, no muffler and has never shut down from heat even here in AZ plus it is very quite 15KW

good luck

Every installation is different, every bus is different, so it is impossible to say what will work!!

One easy and cheap system is to install air dams (mudflaps) underneath the genset compartment openings to help with air pressure.

In general;

A dam aft of an opening increases the pressure for air inflow.

A dam forward of an opening decreases the pressure for air exhaust.

This requires experimentation but the dams are easy to move around if mounted with sheet metal screws.

My gas genset works fine underway but does not like heavy traffic or stopping in hot weather. Diesels seem to adjust to heat better.

John,

I am actually excited. I know the solution to your problems, as we had the exact same issue on our 20KW genset (in a quiet box). Parked it would be great, but driving we would have issues. I will double check tomorrow when it is light, but here is what we did to fix it. Actually we worked with an engineer at EPS to figure out what to do to fix it.

We installed a simple no sail (stiff) mudflap in front of the blower for the genset (right in front of your farthest forward hole). Then install another mudflap just behind your farthest rear hole. I don't know exactly what it does, but it somehow sucks the heat out of there, and allows cool air to circulate up. We have never had another issue with it overheating, parked or driving. It totally fixed that exact same problem with us.

Originally I had a mudflap between the rad output and the main hole under the genset (the hole that draws air in). That totally didn't work. Moving that mudflap forward fixed the issue.

I just noticed that Gus said the same thing, pretty much, that I did. I think it should work for you.

God bless,

John

1. Here is a picture of what my former OTR A/C compartment looked like. We removed the non-working A/C, and added the steel grate on the floor. After that we insulated and added 5/8-inch plywood all around. This is now our generator compartment.

Let me see if I am understanding you kind people. (Front of the bus is to the left.) Should I place a deflector outside, on the right side of the compartment door to force more air in? And another under the bus in front of the grate?

2. My paint-and-body shop friend gave me a double electric fan off of a Dodge Caravan minivan. This will be mounted on the inside of the "baggage" (former A/C compartment) door. I am planning to use a double-pole, double-throw, center off toggle switch, to reverse polarity. It will suck in air going down the road, and blow out air when stopped.  Does that sound like a plan?

3. Has anybody noted any improvement in genny cooling by using synthetic oil in the genny?

Thanks in advance!

I also noticed my genset muffler has a long hole in the seam at the end of the muffler. This muffler is shaped like a car muffler & the size seems that it would fit a small car. Is there a particular muffler I should be using here or am I OK with what I have? And where should I look for a replacement? At my small town auto parts store the attendants get a glazed look over their eyes when I tell them what the muffler is for. They won't even attempt to match up what I have.

   John,   I currently have a diverter across the entrance air hole which is the forward hole but it is placed at the rear as I was attempting to force some air into the opening.  I understand that I may have negative pressure there when the bus is rolling creating a vacuum. Would the placing of the diverter at the front of the forward hole cause a break in the rushing air thereby eliminating the vacuum effect? I can see how the diverter at the rear of the back (exit) hole would cause a vacuum for pulling air out. My generator is placed so the radiator is facing the rear of the bus because the fan blows air through the radiator. So I'm attempting to pull air from front & exhaust to the rear. Is yours placed this way?

John, looking at the photos your problem is the shroud the fan should be inside the shroud not on the outside you have a good fan but you are losing the air flow with the shroud set up.

The Kubota engines are sensitive to exhaust back pressure that will heat one up also I never use a muffler on the Kubota I tape the first 4 ft from the manifold and use about 8 ft of straight pipe and you cannot hear one run.

I had one fan (radiator) a small vent in the bottom of the bay for the head to pull air from it has it's own fan, a sealed door no vent no extra fans and my generator never gave me problems with heat and shut downs and as far as I know it has never gave Matt problems and he runs that babie

good luck

John,

I will try to get a pic today. Ours is set up the exact same way. You are correct. That mudflap needs to go infront of the exhaust hole. It breaks the air. In addition you need another one aft of the intake hole (the big one). It did the trick for us, on a bigger genset, otherwise identical setup (except ours can get even warmer in the quiet box). This is one fix that I am pretty confident of, because we had the exact same thing. Now we can charge and run all five AC's, if we wanted too.

FWIW

John

I could be wrong, but the picture looks like there is no shroud at all around the fan. You need to get one on there.

You are right John does not have a fan shroud he is wasting his time no way can his setup pull a steady vacuum

John, I took some shots of my setup for you today while I was out in the shop.  Mine is similar to yours, albeit certainly not that clean.


I vent mine with some diamond plate air scoops (okie technical term) and I also have another on the inside of the door to direct some of the air towards the radiator.  There are two schools of thought on this, some say it works and some say it doesn't.


I have an exhaust fan that runs whenever the genset is on, it directs the flow of air out of the compartment straight down to the ground.  


Finally, the generator is plumbed through the radiator in the bus itself and has a feed line and return back to the bus.  If the bus overheats, the genset will too, but so far, it has not been a problem.  Over the road heating is not an issue.  It has been out in Clifford's neck of the woods, down south to Phoenix and Tucson in extreme heat of summer (August) and worked just fine.  

If I run it an extended amount of time parked, I will open the doors and let it air out.    We just finished 8 days in a parking lot in Houston because of the unavailability of campsites, running it 24/7 and everything worked well, even when the day time temp's went past 80*.

BCO

In general, you will have positive air pressure in front of an air dam and negative behind it.

This all depends on the air flow around the bus bottom or side, depending on which you are using.

This is not a cut and dried thing and requires trial and error unless you happen to have a bus size wind tunnel!! The air flow around buses is different for each type of bus.

I had them bat wing air scoop thingy's on my MC8 but I never noticed any difference. I finally took them off and to be honest I think it actually stayed cooler without them. And I like the looks of the bus better without them.

Quote from: thomasinnv on June 02, 2012, 10:02:15 PM
I had them bat wing air scoop thingy's on my MC8 but I never noticed any difference. I finally took them off and to be honest I think it actually stayed cooler without them. And I like the looks of the bus better without them.

The appearance of them doesn't bother me, polishing the diamond plate and the maint. on the items, that leaves a lot to be desired on most days. 

As for functionality?

Like I said, "there are two schools of thought on them."  

To each his own.

BCO

Thanks guys. Building a fan shroud is next on the list.
Don, I like your added fan shroud piece & the way it encases the fan even more.
Clifford, That's interesting about the loinger exhaust pipe & no need for a muffler.
I'm sure the fan shroud will help a bunch.

John, you are doing the right thing the box shrouds just don't work the fan you have I believe is a reversible type some are some are not most of those type are the for Kubota's


good luck

i have a small sliding door with a screen behind it that i leave open most of the time. unless i need to actually be really quiet..just a bit noisier, and way cooler.

Don, yours are a bit inconspicuous compared to mine. Yours may serve more of a function than mine did. I was referring to the scoops you see on the upper radiators of the MCI's. They kinda stuck out like a sore thumb on my bus. I think your diamond plate deflectors look kinda cool.

Quote from: gus on June 02, 2012, 02:12:38 PM(snip)  This is not a cut and dried thing and requires trial and error unless you happen to have a bus size wind tunnel!! The air flow around buses is different for each type of bus.  

     It's possible to make a simple tool that may help.   What we're looking for is positive pressure and lower pressure.  Take a piece of 1/4" ID plastic tube (cheap aquarium tube is fine).   Drill about 4 3/16" holes at right angles to each other within the first 6" of one end.  Run the tube out a window (or another easy way to get to your desired location and clip or tape it at the point you're trying to measure.  Tape the other end to a piece of cardboard, thin plywood, scrap sheet, etc.   Draw a horizontal line across the backboard and fill the tube with water until the water level sits right at your line.  Drive the bus and make a mark where the water moves to.  If it's higher towards the open end, you have pressure; if it's lower, you have vacuum at the point where the other end is.  Really simple, pretty quick, and sometimes it can tell you a lot.

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Take a piece of every day yarn and drive the bus it will show all the positive and low pressures on the bus  it doesn't get any easier than that lol not quite as technical as Bruce's idea but it works we call it a poor man wind tunnel.

The Eagle has been in  a wind tunnel for testing Norris had the test reports he told me before he retired but he never sent any too me


good luck

Quote from: john9861 on June 03, 2012, 07:30:00 AM
Thanks guys. Building a fan shroud is next on the list.
Don, I like your added fan shroud piece & the way it encases the fan even more.
Clifford, That's interesting about the loinger exhaust pipe & no need for a muffler.
I'm sure the fan shroud will help a bunch.

Thanks, hope the info and the pictures did you some good.

BCO

Quote from: thomasinnv on June 03, 2012, 08:08:20 AM
Don, yours are a bit inconspicuous compared to mine. Yours may serve more of a function than mine did. I was referring to the scoops you see on the upper radiators of the MCI's. They kinda stuck out like a sore thumb on my bus. I think your diamond plate deflectors look kinda cool.

All in all, I think I have about ten scoops all total.  They are okay until it comes time to polish them, then it is kind of a drag.  My trailer has a diamond plate tool box and diamond plate trim, so as you can readily see, it keeps me out of the beer joints.

BCO