Radiator fan design and radiator size versus efficiency.

[JohnEd]

A Knut recently shared with me his solution to fan energy consumption.  He purchased a REALLY big radiator....way overkill.  He then installed a "modern high efficiency" fan that uses way less power to move a given unit of air.  Lastly he installed a variable clutch/speed control controlled by the engine temp. 

Now I read Cliffs plans to use a more efficient drive and save 50% there alone.  Each of these changes/upgrades will enhance the efficiency or change the HP load.  All of that will change the MPG.  Does anybody have any idea of what each of these upgrades costs so a cost benefit analysis can be done?   Seems this would be of interest to many.  Some of this might be doable in incremental stages.

This isn't the first time I have heard the number of 40 bandied about as the parasitic loss, in HP,  associated with cooling.

Thank you Cliff and probably Sean,

John

[buswarrior]

I'm no engineer....

But from what I've read and heard over the years, there's no free lunch.

If there's 40 HP of cooling power hung out back, and you replace it with 20 HP of cooling....

How is the engine going to stay as cool under loaded conditions as it does now?

Coaches with rear/side radiators are a completely different beast than a front rad mounted truck.

I think we can safely assume that the coach manufacturer did not make an error in installing a cooling system that is grossly wasteful in power consumption.

When in the history of motorized commerce did a fleet owner or a vehicle manufacturer not carefully sweat over the profitable design of the coach?

How do you get air through the rad to shed the heat?

Well, just like the trucks, the new coaches have Horton fan clutches that cut in and out according to need.

However, they spend a VERY large amount of time engaged while driving. Pull over and idle for a few minutes and they cut out pretty much the same as the shutter system closes on an older 2-stroke. Both, by the way, serve the same purpose, reducing the load to turn the fan, the first by disengaging it, the second, by tossing the fan into a low pressure area by closing it in.

The opportunity for "savings" with the cooling system would involve figuring out how to get enough air through the rad without using engine power while you have the kettle on the boil, so to speak.

Remote the rad to the nose and ram some air through it might be a choice?

Or, talk to Fred Hobe about his experiences with some experimental rad intake scoops and an aeronautical engineer...

Don't misintepret my post, you have my support to push the envelope and challenge the conventional wisdom!

But, best be careful with the experiments, that's an expensive engine to be gambling with, in the pursuit of relatively minuscule fuel savings which armies of engineers worried over in the original design of your coach.

happy coaching!
buswarrior

[JohnEd]

TomC, the engineers that design the system left a lot of room for improvement.Eagle are not driven directly from the engine with belts.
They are driven from the front of the engine with a shaft and coupling going into the mitre box with a shaft on each side and another to back on 8v's mitre boxes one shaft goes to the AC the other goes goes to a distribution box to run the alternator and fan that is where your belts start separate belt for each.

BW,

This is where I started.  In brief, 38HP down to 17HP is some serious MPG.  I'll let the experts split the hairs.  And they can do that and we will all be smarter because of it.

Lvr's post went:
The mitre box is a power stealing piece of equipment the guys from Eagle told me it robs 38 hp with a 32 inch fan.   

Hydraulic is not the answer for me either doing the calculations for my setup would still be in the 28 hp range for a fan easy to figure Pressure x Gpm divide by 1714 = HP 

my solution to the problem and I may wrong is to use a angle drive, belt driven with a 2 speed air clutch then I will be in 17 Hp range according to the guys at Horton 

Thanks for the info JLV if your not busy drive down to Breaux Bridge and attend our rally May 1-4
less Hp useage to me is better mileage anyway I figure it    good luck


Luvr never mentioned new generation fan design, shrouding and the increase in cooling efficiency thru specing a larger rad.

Here is my take on the bigger rad idea, and this has already been proved...to my satisfaction but I am still open.  Just like those big fan jets.  The older jets had air moving thru the engine at a rapid clip.  Hi speed air flow is hard to maintain....somebody else can do the math.  They made the turbine fans bigger and moved more air faster and low speed air is easier to do.  Their was a net gain in efficiency and they got their FREE LUNCH.  Good on'em!

If I have a given size rad and it has to shed a given amt of heat...then I will have to push a given amt of air thru it to do that.  If I increase the size of the rad I will need the same amt of air but I can push it slower cause the bigger rad has more heat transferring area.  Slower air means I can use a different design fan.  This all adds up to less energy as far as I can see.  The engineer will tell you how much in every case and a knowledgeable decision can be made.

The time when I need the most cooling is when I am going up hill.  That is also when I have the least ram air at the front.  Given that, I would still put the rad in the front to take advantage of the ram air in all other cases.  There is a project whose time has come.  Seems I read that a electric motor driven fan would be one heck of an affair.  28HP electric motor??  Is 17 any more rational?  Where else can we get ram air for the rad?  Air scoop in the roof at the rear like the old timers had?  HMMMM!

I got nutt'n here.  Somebody smart?

Thanks,

John