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Regular
Location: Clovis, Ca | What temperatures do you think you have in the engine bay? Has anyone measured this?
The reason I am asking this is because with the "pusher" fan, only the engine bay air is being pushed through the radiator.
If the water needs to be cooled to 190* F, but the cooling air (ambient in the engine bay) is 200* F, it just does not make a lot of sense to me.
Jim Black of RVS claims that it gets so hot in the engine bay that metal in-line fuel filters must be used and not plastic as they will melt. To make that happen, it would have to be a LOT hotter than 200*F!
So what is REALLY happening under there temperature-wise?
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Expert
 
Location: Cottage Grove, OR | Jerry - 2010-02-24 4:31 PM So what is REALLY happening under there temperature-wise? Excellent question. I don't have the answer but I can't resist the opprotunity to speculate!
First, you can melt things in the engine compartment without the air temperature being all that high. Radidant heat can pass through the air flow to a stationary object and raise the objects temperature well above the actual temperature of the air flowing past. Second, what is the flow pattern of air in the engine compartment and where is the majority of the air flowing through the radidator actually come from? Is the air for the radiator coming across the engine or is it flowing up from below the engine with the air above and around the engine relatively stable in a low flow environment. If most of the air flowing through the radiator is coming from below or from beside the transmission, that air could be fairly cool compared to the air around the engine. Third, I pass it on to the next speculator! |
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Regular
Location: Clovis, Ca | I have an old VDO mechanical temperature gauge (160 - 320 deg. F) and am tempted to temporarily mount the sensor above the engine to monitor engine bey temperatures.
It would require someone in the back of the coach to read it while driving, but I am VERY curious.
Edited by Jerry 2010-02-25 6:15 AM
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Regular
Location: Santa Cruz, Calif. | My guess is this: We all know that there is a vacuum beneath any vehicle at speed. How much vacuum depends on the air damming up front. This is why race cars have air dams close to the deck: so as much vacuum as possible will pull the car down for better traction.
We also know that any vehicle with bus deminsions has a vacuum in the rear. This is why buses and the back doors of trucks are so filthy. Given this, I would assume the "pusher fan" is assisted by the low pressure at the rear of the vehicle.
Since there is little air coming up from underneath, the engine must be pulling most of it's air from the slipstream alongside the vehicle. Since the "bow wave" spreads out as the vehicle pases, this isn't a lot of air. But it's what there is to work with. I would think the "scoops" to direct air in the side grills would be the most effective, simple solution. A roof scoop would have the same problem unless their intake were up near the front of the coach. |
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Expert
Location: Cottage Grove, OR | Jerry - 2010-02-25 6:14 AM I have an old VDO mechanical temperature gauge (160 - 320 deg. F) and am tempted to temporarily mount the sensor above the engine to monitor engine bey temperatures. It would require someone in the back of the coach to read it while driving, but I am VERY curious. I have thought of doing this as well, but one problem is that I expect that there is a wide range of temperatures that exist in the engine compartment. I expect that above the engine and to the front will yield a much higher temp than above the engine and near the distributor. On either side of the engine, radiant heat from the exhaust system would heat an unshielded temp bulb much higher than the air that is passing by. But I like the idea of testing it! |
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Administrator
Location: Colorado Springs, Colorado | someone running along side with a thermometer, an interesting mental image. |
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Regular
Location: Clovis, Ca | Running really fast!!!
Actually, I am thinking about placing the sensor end in the path of the fan air before it reaches the radiator and running the line out the access door and then in through the fishing pole door. There is inside access from that and someone can sit on the bed and check it.
I am very interested in seeing exactly what temperature air I am pushing through the radiator to cool the water. |
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Expert
Location: Cottage Grove, OR | Jerry, you will need to do it with the sensor near the top of the radiator and again near the bottom of the radiator. Propably need to also do it at either side of it as well sense none of us really know the incoming path of the cooling air. |
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Extreme Veteran
Location: Ignacio Colorado | Inside the shroud between the radiator and the fan will tell you what you want to know. Then you search around the engine compartment for that temperature air, to find the source of cooling air. By the time you get it figured out you should be almost to Minden and you can tell us all in person. Inquireing minds want to know. Also interested in how the engine works out.
Bill |
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Regular
Location: Clovis, Ca | I know this won't be very scientific, but at least it will be a start.
Logically, the cooling air needs to be cooler than the water that it is supposed to cool. Significantly cooler is really what you want (like 100* ambient sir and 200* water)
I know that the back of the rig is a "negative pressure area", but I am wondering if drawing (less) air from a very cool source would be better than pushing a lot of air from a hot source. |
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Expert
Location: Cottage Grove, OR | B. Sitton - 2010-02-26 12:32 PM Inside the shroud between the radiator and the fan will tell you what you want to know. Bill
Dang! I hate it when someone comes up with the simple answer to my complicated problem!! Just kidding, but it does sound like the simple, accuate way to determine the actual temp of the cooling air. I doesn't answer the question of where the air is coming from, but I do have the feeling that the air will be cooler than what most people think it is. Cooling of the engine is done primarily by the radiator, but also by washing the engine with air so one does not want to decrease the air flow over the engine itself either. In my mind, I have toyed with some ways to increase air flow in the top, front of the engine compartment but am not ready to acturally suggest any of them. Some people are already dubious of some of my cooling suggestions (e.g. under the front radiators) so I wll keep it "cool" for now! |
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Regular
Location: Santa Cruz, Calif. | Actually, "washing the engine with cool air" is very important. In several of my mechanic encounters I've been told to keep the engine clean. All that oil & grease traps dirt. This puts an "insulative" coating on the engine. If the cool air can't get to the metal, heat transfer from the engine can't occur.
A couple of mechanics claim that is why new vehicles never overheat. They are too clean to. |
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Regular
Location: Clovis, Ca | Now we are taking a slightly different approach on this
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We decided to pull ambient air in with a 2800 CFM fan on the side door (pass. side).
We will use an aluminum radiator in place of the break-your-back FMC radiator to push all this fresh air from the engine bay through the radiator and out the back.
In case that's not enough, we will have an aux. radiator mounted on the rear door (will swing out with the door) with a temp. controlled electric fan pulling air from the engine bay out the back.
To power all this plus the three transmission cooler fans, we are installing a 300A alternator in addition to the 145 amp stock alternator (the 145 will be dedicated to only charging only the house batteries... No more battery isolator) |
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| RE: engine compartment/componet temps. While I agree with everything I have read from other owners, I am also curious how many FMC's have the tapered vent vanes mounted on the outside of each of the side engine comparment access doors. I guest I was assuming that all righway coaches have the vanes. There is a product/man tag on mine. They are the full size of each door and very well made and, I feel, add to the appearance of the entire coach. And they are made of anodized aluminum which means they will not rust or oxidize. Can anyone tell me what percentage of coaches had these after market cooling vanes? Gene 0638 |
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Regular
Location: Santa Cruz, Calif. | Anyone with a picture? |
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Veteran
Location: Canton, (Sixes) GA | As far as I know, very few have the tapered vents on the access doors any more. There is very little air movement that close to the coach rendering them pretty much useless. There were several discussions on the FMC forum. Denny |
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Veteran
Location: Canton, (Sixes) GA | Make that discussion on the FMC yahoo forum.. ds |
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Expert
Location: Cottage Grove, OR | I removed them from my coach and didn't see any difference in anything. |
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Regular
Location: Clovis, Ca | Not sure if the help or not.
 (2007 Nov 1 B.JPG)
Attachments
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 2007 Nov 1 B.JPG (67KB - 31 downloads)
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Contributor
Location: Gilroy, Ca | Jerry,
The engine compartment temperature on my coach at the power steering pump is +20 degrees above ambient. Test included idle, 0-70 full throttle acceleration, freeway cruise, stop and go. fast response thermocouple was used, sheilded from radiant heat.
Some other thoughts... A radiator with no ram air needs a large fan to provide the airflow. The large brass radiator was most likely chosen for it's design. Flat plates punched for tubes. Large air passages to let debris pass through. Newer radiators with zig zag fins are thin, and are often made with slits in the fins, causing the core to become an air filter. the louvered fins trap debris, even pressure washing can not effectively clean these cores. Keep the dirty air out of your radiator.
Electric Fan Engineering, http://www.electricfanengineering.com/app_off_road_and_bus_turbine_...
has a lot of experience with cooling radiators with no ram air. They have a technical staff that is very knowlegeable. Just don't be scared off by the amp draw of these fans.(up to 100A) Nothing is obtained for free...
Propeller fans are more efficient drawing air through a core. I reccomend a shroud and fan on the outlet side.
My estimation of the pressure differential between the engine compartment and back of coach, 4" water column, or .14 psi I will have to measure this someday. Also on the list is measuring the actual cfm vs. rpm of the stock setup. Need to remove bumper to get flow grid in position.
Stephen said you are making great progress! Keep up the fight. Post pictures!
Eric #587
My $.02 your mileage may vary.
Edited by ericw 2010-03-12 1:54 AM
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Expert
Location: Cottage Grove, OR | I stopped by their place last night (on my returning from Lancaster, CA) and visited with Jerry and looked at the radiator. It is about twice as wide as it is tall. So another option for the fans would be two side by side with one on constant and one temp controlled. Here are sizes that will fit the radiator height. http://www.electricfanengineering.com/app_automotive_turbine_electric_fans.html I believe I would go with two of the 2500-16 units. Tim's brother is joining the work crew as of today per Jerry and that will help move things along. |
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Veteran
Location: Oslo Norway | Thank you Eric, great link.
Those kind of sources for parts is always welcome. In a distant future I'll add a custom made aluminum radiator and electric fan to the Dancing Queen.
Stay cool
Kjetil
#477 |
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Temps in the engine bay?
