Radiator Trivia

[pvcces]

David, I did a little math on the numbers that you furnished. The 12000 btu number was per minute, I figured, which meant that the btu/hr comes to 720,000.

Using your horsepower figure of 315 and allowing 1 gph per 15 hp for a good condition 2 stroke, I got a maximum fuel consumption of 21 gph. That much fuel per hour has nearly 3 million btu. On the older diesels, about 1/3 of the energy from the fuel will wind up in the cooling system; in this case, that would be 1 million btu at the maximum power of the engine.

Any additional heat from charge air or transmission will only raise that number. A 6V92TA with a V730 might go as much as 50% higher.

I didn't see where you mentioned what temperature difference between the coolant and the cooling air would give you the 12,000 btu/min, but it does seem to me that if you tried mountain climbing on a hot summer day, it might be pretty easy to hit the limit of your cooling.

For what it's worth.

Tom Caffrey
Suncatcher
Ketchikan, Alaska

[David Anderson]

Tom,

That is too much fuel.  I get about 6.5mpg.  At 70mph or 70/6.5= 10~11 gallons per hour.  The 6v92 is rated for 10k btu/min heat rejection.  That is what I was told my radiator was rated.  I'm a little short when it comes to mountain climbs and the tranny is in 1st gear dumping extra heat into the radiator.

David

[pvcces]

David, it seems to me that you're saying your average fuel consumption is about 1/2 of the maximum that I calculated. It seems to me that you are getting what my numbers seem to show. Most of the time, there would be no overheating.

The only time that I would think that you would see overheating is when conditions were bad. Our coach doesn't run the fan at full power unless the coolant is hot enough. Because of the horsepower that the fan uses, it pays to keep the radiator in good enough shape that the fan runs as little as possible.

In the end, you are the only one that can decide how much cooling that you will need. I did the calculations to show how you could arrive at a solution to your question of whether the radiator would have enough capacity for your use.

Good luck with your cooling.

Tom Caffrey
Suncatcher
Ketchikan, Alaska

[David Anderson]

Thanks Tom,

I picked up my 16 blade fan yesterday.  It fits right on the hub.  The fan is huge!!  I've been engineering a new shroud for this made from 14 gauge steel.  I got most of it fabricated today and this will beat the heck out of that puny fiberglass shroud.   I'm really encouraged about doing this because Texas Custom Coach installed this fan on 3 different Eagles with 8v92's and it totally solved their problem.  Gene Rochester installed a larger fan on his 500hp eagle and kicked his problem, too.  I'm not making mine spin faster with this installation.  I wanted to try it stock, first. 

So, there you have it.  I had the chief engineer from Atlas Radiator (who made them for Eagle) tell me to move more air.
I have Gene telling me to move more air.
TX Custom Coach moved more air. 

By golly, I'm gonna move more air across my radiator.  Hopefully I'll have this done by Monday for a test run.  It is still 103 here and I'd like to get the coach out while it is still blistering hot.

David

[Burgermeister]

1. What did you use for a build reference when making your shroud?

2. What radii did you use for the shroud transitions? 

3. How far will the fan "insert" into the shroud? 

4. Do the fan tips match the radius of curvature of the exit shroud?

5. Do you plan on checking pressure drop within the shroud against ambient with a manometer BEFORE YOU GET TO PEAK RPM?

6. You say the fan was huge but will be spun at the same RPM.  Did you perform a tip speed calculation (Pi x diameter x (max) RPM= ??)

7.  Are you sure you want to test to peak RPM before performing #s 5 and 6?

8.  If your answer to  7 is yes,  I'd advise you make sure nothing (person or property) important is both close and in the plane of the fan's rotation!

Good Luck!

Onward and Upward

Marc Bourget

[David Anderson]

1. What did you use for a build reference when making your shroud?
The fan diameter
2. What radii did you use for the shroud transitions? 
Not sure what you mean.
3. How far will the fan "insert" into the shroud? 
The blade edge is even with the radiator side of the shroud and about 3/4" of the edge is outside the shroud (towards the engine)
4. Do the fan tips match the radius of curvature of the exit shroud?
Not sure what you mean
5. Do you plan on checking pressure drop within the shroud against ambient with a manometer BEFORE YOU GET TO PEAK RPM?
No
6. You say the fan was huge but will be spun at the same RPM.  Did you perform a tip speed calculation (Pi x diameter x (max) RPM= ??)
No
7.  Are you sure you want to test to peak RPM before performing #s 5 and 6?
Yes
8.  If your answer to  7 is yes,  I'd advise you make sure nothing (person or property) important is both close and in the plane of the fan's rotation!

Ok.

I finally got all this together and took it out for a test run.  The ambient temperature was 100.  I pushed the coach to 75 and maxed out the turbo boost as best I could.  The gauge never went above 184.  My t-stats are full open at 185.  The most impressive result is my delta.  I made a quick stop on the roadside when I got it as hot as I could.  My inlet temp in the radiator was 184 and my outlet temp on the suction pipe to the water pump was 150.    Never, ever have I achieved better than a delta of 10. 

When I put the coach at high idle I almost get sucked in when I walk by the radiator.  The fan sounds similar to a jet turbine.   This fan was pitched for an Eagle by the manufacturer, so I assume all the engineering is good.

As far as the shroud construction, I just boxed in the entire radiator hole in the bus.  the whole radiator is sealed into the hole.  This eliminated any need for compound curves on the shroud.   It is flat steel with a hole in it and a 1" ring for strength.   The whole thing is pretty stout as I wanted NO wiggle or flutter anywhere in the shroud. 

I have a 1200 mile trip on the 16th.  That will be a good test.

David
David

[Brian Diehl]

Awesome David!  Good job putting it together.

Question:  Did you use some sort of thermostatically or manually controlled clutch on the fan so you aren't consuming power when you don't need maximum cooling (like in the winter)?

[David Anderson]

No,

That is more money.  Maybe next year.  I figured when I'm going 75 on the flat it won't make much difference with the fan running full speed anyway.  When I'm climbing that long hill, the engine will require all the fan I can muster to relieve the heat.   My fan is direct belt and pulley drive off the miter box, and I use 180 t-stats, so I have no trouble keeping the temp up even in cold weather. 

The fan cost me $472 from Goodson Bus Sales 828-428-4102.  The parts for the shroud were about $112 bought from my local metal supplier.  It took me about 12 hours to get it all together.  I did have the welder cut the hole with a plasma cutter.  He did a perfect job.  That was included in the $112.

David

[David Anderson]

We just finished a 1300 mile trip up IH 35 to Kansas and back.  The engine never bumped above 185 on the engine room gauge (full open t-stat is 185).  It was only 95 degrees ambient and just a few rolling hills through central Texas, but I'm impressed with the results.  I do have a sense that the engine room may get too cool in the winter.   However, I never saw the cockpit gauge fall below 170 while driving.  I may be throwing blankets over the intake next winter. 

Where and what would I look for in a thermostatically controlled fan clutch, and how much would such a beast cost?

David

[Burgermeister]

Dave,

Excuse me, but what engine do you have in your bus?

Stock cooling configuration, including sizes of hoses and fittings.

Do you have access to a magnahelic or manometer to check the "Delta P" between the core and shroud and before the fan?

It would be ironic if you have adequate radiator and fan whose efforts are being defeated by an aeration problem.

[David Anderson]

Excuse me, but what engine do you have in your bus?
6v92 set at an anemic 315 hp with the throttle delay to minimize smoke. 

Stock cooling configuration, including sizes of hoses and fittings.
5 row radiator OEM for a 1985 model 10, 41" wide.  I believe the fittings are 2".

Do you have access to a magnahelic or manometer to check the "Delta P" between the core and shroud and before the fan?
No I don't, but I wonder if I could accurately measure the core front and back (through the fan blades) with my temp gun??  Never tried it that way.

It would be ironic if you have adequate radiator and fan whose efforts are being defeated by an aeration problem. 
I was told by two engineers that the radiator was adequate, thus my valiant search for a better fan.  Thanks to Dave at Texas Custom Coach in Pipe Creek TX, I feel like I've found the right fan.  He suggested it and steered me to Goodson Bus Sales to buy it.

David

[Burgermeister]

David,

The adequacy of the radiator is irrelevant if the coolant is experiencing aeration.  But if it's a stock system and no internal corrosion,  I'd suspect that it's alright.

I'm trying to make Arcadia with a special type of manometer setup to check Cooking System Delta P (Pressure)  If you're around then, and wish to serve as a "guinea pig", the test will give a good indication if the system is aerating the coolant.

Marc Bourget

[Happycampersrus]

How does the fan air pressure affect the aeration of the engine coolant?

If you check the air flow with a manometer, How can that tell you if your coolant is aerating?

Just curious!

When I built my cooling system I used a piece of clear hose, then used my backup camera to check out the flow while driving.

FWIW,
Dale

[Ace]

Hey that's good news Marc! It'll be nice to finally see your bus and work in progress! I know it's beena long long hard road getting it to where you can use it but I'm sure it will be worth the trip for you and everyone else that finally will have the opportunity to see all that knowledge put to good use!

Ace!

[Happycampersrus]