Radiator fan consumes over 10% of engine HP!

[Lin]

In preparation for our summer trip, I have installed an air dam/mudflap behind the drive wheels, did some extra sealing around the blower compartment, and am having scoops made per Fred Hobie's design.  My hope is to avoid any hot running going up the Eastern Sierras.  If it works well, I may not be able to say for sure which fix gets most of the credit.  If I run hot, then maybe none really work.  I will let you know come August.

Anyway, I was wondering if replacing the wire mesh on the intake grill with forward facing louvers slightly extended beyond the skin.  That would seem to be a way to breakup the laminar air effect.

[usbusin]

If I remember correctly, it has been 10 years now since I've had my 4104; I took a piece of 1-1/2" x 1-1/2' stiff cardboard with legs (  __/\__  ) and placed it with both "legs" on the bus skin.  Taped it on to see if it would help in getting more air into the radiator. 

It seemed to help, so I formed a piece from .060" alum with extra legs (  __/\__  ) and riveted it to the bus skin.  You have to experiment with the distance in front of the radiator opening. 

Tape some yarn in front of, on the "vee" and on the radiator opening; take her for a drive and see what happens with the yarn.  A poor mans wind tunnel.

[lostagain]

My 5C came with those ear rad scoops. I removed them. The only difference that I can see is that the bus looks better without them

It doesn't run any hotter without them going up hill on a hot summer day.

I am going to try a lip just ahead of the rad grills.

JC

[JohnEd]

I suggest not making the lip a "ramp".  The lip should be vert to the side of the bus and be at the edge of the opening.  I would do this even with a scoop.

[RoyJ]

The MCI-D models still have the two rads and two fans mounted high in the rear with side intakes. The new ones have a HUGE fan because the new motors run hot for pollution control and the rads need to keep things tame. Stop by MCI and have a look at one. My experience, though I don't do northern winter driving, is that the top mount rads stay much cleaner than the side mounts. Of course the engine bay is much more accessible.

If the operating temp of the engine goes up, it's actually easier to cool. Heat transfer rate is linear to delta-T (of coolant vs ambient). When I worked in fuel cell design, one of the greatest challenges is cooling, because you're dealing with a cell operating at 150F or so, but putting out the heat of a 2 stroke Detroit. Not only that, all fans have to be electric!

On the other hand, the extra heat rejection of the EGR might have something to do with it.

I'm gonna guess the primary reason is higher effiency of a larger fan and radiator, as previously mentioned in this thread.

[bevans6]

I'm not sure of the logic of putting a lip ahead of the radiator.  That will create a low pressure zone behind the lip, making it harder for air to get into the radiator.  A lip behind the rad might do something.  similarly, why would you want to create chaotic air at the rad intake?  Smoothly flowing air will create the highest pressure zone, hence the greatest flow into the radiator.

Brian

[robertglines1]

I have kept quiet for afraid of spoiling a good thing I enjoy. I have a variable speed clutch set up stock from prevost on my 89 with a 8-v92. My main concern in late 90 degree heat towing a load is keeping the temp high enough for good performance. I fought overheating with the MCI 8-new rad,scoops and misters. No good reason as to why: I don't know the science but enjoy the results. Yes I have verified gauges with IF and mechanical Gauge check. Probably should have NOT mentioned it; Knocked on wood!  Bob

[JohnEd]

Your right Bob.  You shouldn't have mentioned it.

Just kidding now.  I am sure there is a lot of disbelief around here at this moment.

John

[JohnEd]

I'm not sure of the logic of putting a lip ahead of the radiator.  That will create a low pressure zone behind the lip, making it harder for air to get into the radiator.  A lip behind the rad might do something.  similarly, why would you want to create chaotic air at the rad intake?  Smoothly flowing air will create the highest pressure zone, hence the greatest flow into the radiator opening.  Can't be much.

Brian

Brian,

You hit the nail on the head.  The trailing low pressure is supposed to bend the air flow into the opening.  It isn't my lie but it sure made sense to me.  If you bend the lip towards the origin of the flow it will make the air current cutoff very sharp and reduce turbulence.  The air was virtually still on my patio above the Pacific but if you raised your arm the wind was passing overhead at 10-20 MPH.

Many years ago I replaced my exhaust manifolds on the 440.  In their place I installed Doug Thorley Tri Y headers.  While I had it down I wanted to port and polish the heads a little.  What I discovered was that the heads had a HUGE ridge cast into the top of the exhaust port.  That "bump" across the entire width of the port was choking up the port by at least 20% in my estimation.  No wouldn't you think those Chrysler engineers would have been smarter than that.  Drawing on my education porting my dirt bikes I had learned that removing material from the inside of a turn was a no-no as that radius turned the air flow.  My porting manual for the 440 didn't mention that so I had to ponder it and figure it ouit for myself.  The exhaust manifold on those stock 440's turned up and the manifold ran parallel to the valve covers.  The headers swept DOWN so those bumps would have killed the performance of the headers.  I ground them off.  Some of the common sense would lead to the conclusion that the bump would deflect the gas flow and that isn't the case.  I will stake my ME degree that I don't have on this.   There are guys on here that build and race cars, sooo ?

John

[lostagain]

Brian, John, so now I am confused. Nothing new though... So for lack of any logical evidence, I will do nothing else to may radiators air intake. The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.

JC

[RJ]

The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.

Truer words were never spoken!

[RoyJ]

The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.

Truer words were never spoken!

But where's the fun in that!

So much better to mash the pedal to the floor, watch the smoke build up, pass a couple old yellow motorhomes, and then get to the top of the hill overheated and buzzer beeping, pull over, and start comlaining about the need for a new fan, rad, or engine swap 

[luvrbus]

You MCI guys were screwed from the factory with their setup not enough radiator,air movement and trying to pump water up hill same water pump will circulate enough to keep a 12v71 cool with the right radiator and fan.
Going to Kingman today I saw 4 MCI 9's and one 102A half way up the grade off to the side of the road cooling off the A looked like it lost engine is was blowing smoke and it is not hot here yet 103 today

good luck

[Lin]

Clifford,

I think that the MCI engineers did a wonderful job and really put their theoretical education to use.  The only problem is that it seems they missed the class that taught Murphy's Law.

[artvonne]

  Pumping water up hill isnt a problem if your pumping it to a tank that feeds the pump, then its just circulating. And as hot water wants to rise, and cool water wants to fall, I think the MCI is simply using that natural tendency.

  The thread seems to be drifting to heat and radiation, where the original topic centers on the power consumed by the cooling system, specifically the fan.

  It's been suggested in other threads that the MCI's (5's through 9's etc..) are pulling as much as 50 HP off the engine for cooling. Some of the arguments centered around the belt size and its HP rating. But simply looking at the fans, they sure dont look like a pair of 25 HP blowers. No, they look about the size of a residential furnace fan blower, maybe a bit bigger. I should go measure before I stick my foot in my mouth, but they look no larger than the fans in the condensor bay. The pulleys are about simular in size from engine to gearbox, and assuming 1:1 through the box (I dont know) one could guess the blowers are running around engine speed. So Cliffords observation of an MCI fan drive being replaced with a condensor fan motor should be given some weight. IOW, it propbably needs more than 2HP worth of fans on a hot day, but nothing approaching 50 HP. The belt used is likely more for endurance.

  While the idea of a lip ahead of the intake might sound good on paper, without some kind of testing your shooting in the dark. Its just as likely to screw up the airflow and blow over the intake rather than let it fall in.

  In any case, and on ANY Bus, GM, MCI, Dina, the first order of business should be to keep everything clean and clear. Fans can lose as much as 50% air flow with visible dirt on the blades. Radiators need to be clean and clear as well. Anything that air has to flow through, screens, vanes, all create obstacles that impede air flow. Turns create big obstacles. A 90 degree turn in a 4 inch pipe is equal to 4 feet of pipe in reduced air flow.

  And as Bob pointed out above, lifting your right foot has the biggest effect of all. Slow down the engine you slow down the fan, reduce the wind resistance load, use less power, make less heat, burn less fuel. And its not linear, its square. a 10% reduction in speed makes roughly a 40% reduction in required power. With fuel prices what they are and so many expenses coming at us simutaneously, weddings, buying a Bus etc., I decided to drive the Bounder without my foot planted hard on the floor as I have. I drove to Minnesota and back last month, and instead of 6'ish mpg at 70 plus, as ive been used to getting, I pulled off almost 10 mpg at a more sedate 55-60. And while the slowness drags out the trip, the reduced speed reduced the wind noise, the ride was better, the engine was quieter, and I wasnt fighting the wheel as much as I was used to.