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Old 06-05-2015, 09:33 AM   #29
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Location: Lighthouse RV Resort, Melissa TX
Posts: 3,560
Some interesting thoughts in here. According to RV builders the no.1 reason for side radiators: SPACE.

A rear radiator will move the engine, transmission and axles forward 18-24 inches. Move the radiator to the side and everything slides back. Very important when above 9 liters.

Both will cool just fine. Rear radiator coaches have a larger radiator to make up for the warmer air used during cooling.

According to Freightliner my coaches fan can draw up to 60 hp on high.

Here is from a Cummins PDF.

Fan Operation
The typical on-highway fan run time hits a year round average of 5-7%. It takes between 10
and 70 horsepower to drive the cooling fan. An inoperative fan clutch, faulty thermostatic
switch, low coolant level or other malfunction that makes the fan run longer can take a big
bite out of the fuel economy of the vehicle. Cooling system maintenance can have a
significant effect on fuel economy.
Table 5: Typical Heavy-Duty Fan Power Requirements
1100 9 10
1300 14 17
1500 22 26
1700 32 37
1900 45 52
2100 61 70
At 1450 rpm, cruise operation, the fan being locked on can cause an 8-12% mpg penalty
(assumes 225 hp road load).

From here:


2013 DSDP 4347, all electric, 450 H.P. ISL
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14 Jeep Grand Cherokee Overland toad
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Old 06-05-2015, 07:33 PM   #30
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Originally Posted by Dutch Star Don View Post
"Crasher"..... you're saying that your coach defies physics? So your coach sucks air in from the driver's side, enters the engine compartment and then makes a right turn and goes out the back??? Have you ever stood on the passenger side at idle and felt the air blowing out?
There is no way for air to blow out the passenger side on my coach. The chassis batteries and electrical controls are in compartments to the passenger side next to the engine. To push the warm air across the engine, then force it down below the compartments and out below them when the rear is open would have to defy physics. No, I have not felt air coming out the side, but I have stood at the rear of the coach while it was idling and felt the warm air blowing out the rear. It would be even more pronounced at speed with the help of the vacuum created at the rear of the coach.

2013 43 QGP Allegro Bus
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Old 06-05-2015, 07:57 PM   #31
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Well I guess your fan sits high on your chassis and blows NOTHING under the engine. My chassis will part your hair on the passenger side. By the way there is a void created at the rear of the coach, so air is not sucked out at speed.
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
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Old 06-05-2015, 09:25 PM   #32
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Now, I'll have to check my son's 2015 45' Mountain Aire to see where the fan is mounted and where the air flows. According to your theory, the rear of the coach could be sealed up and not effect cooling as all the cooling air is going out the side.
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Old 06-06-2015, 07:04 AM   #33
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Originally Posted by Dutch Star Don View Post
By the way there is a void created at the rear of the coach, so air is not sucked out at speed.
That "void" is a region of low pressure air created by the coach moving out of that space at speed. Being lower pressure than the surrounding air, it will suck in air from all directions, most often from the area behind the coach, which is why so much dust and dirt tends to coat the back of the coach.

If there is high pressure air in the engine compartment caused by the side radiator fan drawing in air, and there are louvers/vents in the rear of the coach between the high pressure air in the engine compartment and the low pressure air behind the coach, I don't see how a lot of air wouldn't be flowing out those louvers. Air will always try to even out the pressures and will move from areas of high pressure to low pressure.

Adam and Sue, and a pack of little furballs
2007 Holiday Rambler Endeavor 40PDQ Limited Edition - Cummins ISL 400
2013 Ford F-150 FX4 toad - USGear Unified Tow Brake, Roadmaster Blackhawk II Tow bar, Blue Ox baseplate
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engine, vent

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