Another Mister Question

[Lin]

Without getting into the pros and cons of misters since I have already started to install some, I wanted to ask a question of those the have systems they are satisfied with.  I am running mine off the fresh water tank, so there is pretty good pressure.  My thought was that I am not really looking to mist the air but to spray enough water into the airflow to give quick bursts of cooling.  I was just going to use some PVC pipe and drill some holes in them to create the spray.  However, in my experiment today, I found that a group if 8 holes that were 1/16" each was shooting probably too much water too far.  What hole size has anyone found to work well, or do I need to actually buy some special mister inserts?

[lostagain]

I would start with 1/64th. You can always drill them out bigger later. 8 holes is lots, so they don't need to be big.

JC

[buswarrior]

You are conducting your tests with the fans running at high speed?

With the high air flow when driving, the water streams will be bending quite hard into the rads.

happy coaching!
buswarrior

[Geoff]

I use the adjustable spray tips (8 each) sold in the drip irrigation section of Home Depot. I also use their drip hose and 24v solenoid to activate the sprayers with water coming under pressure from the fresh water tanks.  I have installed this system in a few buses, works well.   When the temp gauge starts going up climbing a hill I give it a 5 second shot, wait a little bit and give here another shot.  The engine temps go down withing a couple of minutes.

[Lin]

BW- No, I did not conduct the test in the fan stream, which would be better. However, I consider this a little less precise than rocket science, so I thought I could estimate from my test on the ground.  It seems that with 8 the holes 1/32 will be okay. I could, of course, enlarge them in the future.  I tested a mister emiter and thought it a bit weak though. I am counting on the air flow to really mix up and distribute the water.  I would guess that whatever water is not sucked directly into the radiator will evaporate and serve to lower the air temperature a bit. That is why I believe the holes would work as good as a spray head of some sort.

Geoff- Funny you should mention the valve.  I bought a 24v solenoid valve on ebay.  It took forever to arrive from China.  I was just at HD this morning and saw that their irrigation valves were also 24v.  Oh well, now I know where to get a replacement fast.  The one I got is brass, which was not necessary.

[TomC]

At first I installed 15 misters from Home Depot.  They worked so-so. What really worked well was to drill out just two of the lowest misters with 1/16".  Now we're talking lots of water.  It is hooked to my water system with a 12v solenoid valve.  Pleased with it-course wish I didn't need them, but over 90 pulling a hill usually do.  Good Luck, TomC

[luvrbus]

Lin you know I am not a big mister fan lol but keep the holes small and use the Shurflo 8002 high pressure pump 100# vs the 40# makes a world of difference with cooling ,useage and maintaince problems and it comes in 24v also

[Ace]

My mister actually broke meaning i lost one of the spray heads. Now water just sort of gushes out but it cools the motor down faster that way than when it was working with a good spray head!
Go figure, science!


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[Lin]

Clifford, I agree with you about misters being a very inelegant fix, but short of spending the money on really redoing the cooling system, they are an option.  If you really want to laugh, I am putting some scoops on also.  I just do not want to have to worry about the temps on grades or pull over for cool downs anymore.  The temps have gotten pretty high a couple of times in the past and hopefully I have not compromised the engine in ways that have not shown themselves yet.  I have not checked the pressure on my house pump, but it is putting out a lot of water.  Since we are planning, as some here have done, to use short burst of high volume water, that would seem to be what I need.

Ace- Although some say they have success with using an actual mist spray, I have my doubts about that being best.  Saturating the air with water lowers its temperature.  They call that the wet bulb temperature as opposed to dry bulb temperature.  Misting is an attempt to lower the dry bulb temperature by adding humidity to bring the air down to the wet bulb temperature.  That's what swamp coolers and porch misters do.  I am not sure that putting up a mist a few inches in front of the radiator is the most efficient approach though.  I think, as seems to be confirmed by your experience, a little bit of flooding goes a long way.  This is one reason I have chosen to use the main water tank where there is enough capacity that running out of water is not a concern.  Minerals are, but I believe that if one stays ahead of the accumulation by cleaning the radiators often, it should not get critical. 

[buswarrior]

If you are putting on radiator scoops, look at the ones on Fred Hobe's site:

http://users.cwnet.com/thall/fredhobe6.htm

IIRC, you need the scoops to come forward at least 1/3 of the width of the screen, and stick out 3 inches. Easy on a 96 wide coach, a regulatory problem for a 102 wide coach.

The ones on Fred's coach in the picture work well, but he did some work beyond those ones...

Fred shared a story with a few of us once about some work he did with an aeronautical engineer for fun, and in their messing around, came up with a working model that pulled in more air than the cooling fans could ingest!

The trouble with smaller scoops, they encourage the air to curl in front of the rad and then curl right back out. It was theorized that some installs may actually be reducing the air flow by disrupting it.

You need a design that ingests the air and doesn't let it roll back out.

Imagine running a military spec 8V71T, opening the MCI fan compartment door on a hot Florida day, defeating the cooling fans, and then pulling onto the highway to do a high speed run... Temps went up, and then went right back down and stayed there with the fan door hanging open.

Some money would need to be spent proving the concept, and there's no hope for a return. As some of us know, there is no money to be made from busnuts, who don't buy stuff, they copy, the design can't be legally used on a wide body coach, and Fred's current scoops do the job, so that's as far as the work went.

So it remains an interesting story, told one evening amongst friends, at one of Jack's New Year's rallies.

happy coaching!
buswarrior

[Lin]

BW, I have used Fred Hobie's website as the model for the scoops.  The difference is that I am having these made an inch longer than his since the 5a has more of a curve in the back.  I have heard mixed stories about scoops but, if they work right should help generally on the open road with mild inclines.  I do not think they would help much on serious grades though because you are moving so slowly, hence the mister.

I did once meet a guy with a 5a that claimed he was a retired propeller designer.  He had replaced his 8v71 with a 6v92 without doing any cooling modifications.  He said that scoops and opening the engine doors a bit were just enough to get buy.  The thing is though that he was from Canada, so even though we were near Death Valley, he was not in the real critical conditions.  It very well might not have been adequate in the summer there, but the point is that they did help him for what use they had.

[edvanland]

Geoff replaced our system with his on our 8V92 with automatic in our MCI 7 and what a difference. I had already done the new radiators, a extra radiator, scoops and #*&%@ and after he put his system on ours it works great. When you live in central Arizona we have a long hill to climb no matter which way we go.
Thanks Geoff
ED & Janet

[luvrbus]

Enlighted me here guys why so many heads on a system I have been around a few Hyden self contained systems they have a high pressure pump and hold 2.5 gals of water the most heads I have seen on those units are 2 and everyone here that has one say they work I still like bigger radiators and good airflow 

[Lin]

Clifford, maybe it's just over kill.  I would not say that what I've done really qualifies as being engineered.  Are the factory systems you know of used for short bursts or left on for a while?  I have put mine on my old spring loaded reverse switch, so it will stay on only as long as I hold it, which I hope is not long.  Big radiators and good air flow rule!!  I have a nice big recore radiator over at Don's.  I thought of hanging it out the back or putting it on the roof, but that has it's drawbacks too.

[lvmci]

Hi All, if you have one radiator that mists more than the other side, on a MCI, is there a negative impact on the engine (8V71), of course they're only on for short periods, lvmci...