Home » Public Forums » GMCnet » [GMCnet] ELECTRIC RADIATOR FANS
| [GMCnet] ELECTRIC RADIATOR FANS [message #61334] |
Fri, 23 October 2009 16:15  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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I guess I don't know of a single, successful, full conversion to Electric
fans on a GMC, that is on the road today. (I will post it if there is)
If you read the literature:
http://gmcmotorhome.info/engine.html#electric
Even with extensive mods to the electrical and cooling system, this mod has
not proven to be a cost-effective, or workable modification. It seems the
best work on this is being done by Gene
Dotson, so I guess we will see what comes of his work.
So even if you want to do it, because you can, you are not likely to beat
the OEM , fan clutch configuration. Especially here on the left coast where
there are hills / mountains to climb.
JMHO
gene
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61406 is a reply to message #61394] |
Fri, 23 October 2009 22:32  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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There was a big discussion on this on the revcon board and the consensus was that it was not viable. But I think we might suffer from intelectual incest. We give the most credit to people with GMC/REVCON expertise. But really, it's just an engine and a radiator. Maybe someone else knows more about it than we do.
So I poked around the net and found that the offraod crowd uses electric fans on big blocks moving at very slow speed under pretty serious load.
They say to use a fan off a Tauris or a Lincoln. Not sure what years.
I don't claim any expertise here myself. Maybe an RV is different. But the Car industry keeps putting electric fans on bigger and bigger vehicles, they must know something.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61421 is a reply to message #61334] |
Sat, 24 October 2009 02:51 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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I had a 1993 S10 Blazer. I installed two electric fans to help the engine fan in heavy Phoenix summer traffic. that was the last year of R12, and I bought the truck partially for that reason in 1995. the AC never worked well in it, but the fans definitely helped...
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61440 is a reply to message #61438] |
Sat, 24 October 2009 10:36 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Terry;
Finally, the guy who actually knows that even a single 16" haywired
electric fan can cool a GMC adequately, while towing 4000 pounds. Is it
all down hill from Colorado to Roy, WA.?
Thanks;
Gordon
Terry Skinner wrote:
> I think the biggest problem the GMC has is the distance between the
> fan and the radiator. Back in the days when we did a lot of engine
> conversions we tried to get the fan as close to the radiator as
> possible. the shroud on the GMC is a bandage on the problem. If you
> look at the newer race cars they devote a lot of effort into ducting
> air into the radiator, not out. We would do well to look at shrouds on
> both sides of the radiator and a plate across the frame to keep the
> turbulent air from coming up from the road disturbing air flow into
> the radiator. This summer on a trip back from Colorado I used a 16
> inch electric fan in front of the radiator when the fan clutch went
> out. Worked good even with a 4000 pound towd on the back. Ambiant
> temperatures were in the high 90's. My plan is to look into this a lot
> farther. Really tired of changing fan clutches. And yes, I have
> changed the clutch out the top without removing the shroud. I have the
> bloody knuckles to prove it...........Terry
>
> On Sat, Oct 24, 2009 at 6:41 AM, Matt Colie <mcolie@chartermi.net> wrote:
>>
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61444 is a reply to message #61438] |
Sat, 24 October 2009 11:19 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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The reason all the Toro's had an engine-mounted fan shroud was to reduce the tip clearance on the fan, which is the dominant influence on fan efficiency. Note that many of the electric fans have an outer ring, making the tip clearance zero. It wouldn't hurt to have the fan closer to the radiator, but if you gave up the tight tip clearance I doubt if anything would be gained.
Newer cars have had a lot of attention given to underhood aerodynamics. Yeah, it's not obvious by a casual look, but how the air gets out is just as important as how it gets in. Note the louvers in some inner fenders - they are put in a low pressure area to draw air out and into the wheel well area, which is a good exit. The GMC looks to me like no one paid attention to how the air got in OR out of the radiator. Just because the radiator faces forward doesn't mean that the air just naturally goes from front to back. Why would it - it can go around the bottom, sides and top just as easily. I had an airplane that developed an oil leak (don't they all) and some of the oil streaks went OUT one of the air inlets. Yup, air was going in one side and out the other even though both faced forward.
Terry has point - maybe with good aero design and a good electric fan the engine fan could be eliminated. Don't know.
Gary
________________________________
From: Terry Skinner <gmcnut@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Sat, October 24, 2009 8:51:50 AM
Subject: Re: [GMCnet] ELECTRIC RADIATOR FANS
I think the biggest problem the GMC has is the distance between the
fan and the radiator. Back in the days when we did a lot of engine
conversions we tried to get the fan as close to the radiator as
possible. the shroud on the GMC is a bandage on the problem. If you
look at the newer race cars they devote a lot of effort into ducting
air into the radiator, not out. We would do well to look at shrouds on
both sides of the radiator and a plate across the frame to keep the
turbulent air from coming up from the road disturbing air flow into
the radiator. This summer on a trip back from Colorado I used a 16
inch electric fan in front of the radiator when the fan clutch went
out. Worked good even with a 4000 pound towd on the back. Ambiant
temperatures were in the high 90's. My plan is to look into this a lot
farther. Really tired of changing fan clutches. And yes, I have
changed the clutch out the top without removing the shroud. I have the
bloody knuckles to prove it...........Terry
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61448 is a reply to message #61444] |
Sat, 24 October 2009 11:42 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Senior Member |
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Gary;
Around 1970, I became aware of the Kort Nozzle and how much it improved
the bollard pull on a marine propeller. I convince Campbell Marine
propeller to do some testing on a standard marine prop with a ring
mounted to the tips. I don't remember the gain, but it was significant.
The problem in B.C. was we have so much junk in the water, the potential
for increased damage to the prop and rudder negated the benefit. If a 4
x 4 got in the prop, it could stay there for a few revolutions and beat
things up. Now most of the props on small auxiliary outboards, used to
drive large vessels at low speed, have a ring on the tips. On the
aircraft prop, you have the "Q-Tip" and on the wings you have the
winglet for the similar reasons.
Gordon "ad nauseum"
Gary Casey wrote:
> The reason all the Toro's had an engine-mounted fan shroud was to
> reduce the tip clearance on the fan, which is the dominant influence
> on fan efficiency. Note that many of the electric fans have an outer
> ring, making the tip clearance zero. It wouldn't hurt to have the
> fan closer to the radiator, but if you gave up the tight tip
> clearance I doubt if anything would be gained. Newer cars have had a
> lot of attention given to underhood aerodynamics. Yeah, it's not
> obvious by a casual look, but how the air gets out is just as
> important as how it gets in. Note the louvers in some inner fenders
> - they are put in a low pressure area to draw air out and into the
> wheel well area, which is a good exit. The GMC looks to me like no
> one paid attention to how the air got in OR out of the radiator.
> Just because the radiator faces forward doesn't mean that the air
> just naturally goes from front to back. Why would it - it can go
> around the bottom, sides and top just as easily. I had an airplane
> that developed an oil leak (don't they all) and some of the oil
> streaks went OUT one of the air inlets. Yup, air was going in one
> side and out the other even though both faced forward.
>
> Terry has point - maybe with good aero design and a good electric
> fan the engine fan could be eliminated. Don't know. Gary
>
>
>
> ________________________________ From: Terry Skinner
> <gmcnut@gmail.com> To: gmclist@temp.gmcnet.org Sent: Sat, October 24,
> 2009 8:51:50 AM Subject: Re: [GMCnet] ELECTRIC RADIATOR FANS
>
> I think the biggest problem the GMC has is the distance between the
> fan and the radiator. Back in the days when we did a lot of engine
> conversions we tried to get the fan as close to the radiator as
> possible. the shroud on the GMC is a bandage on the problem. If you
> look at the newer race cars they devote a lot of effort into ducting
> air into the radiator, not out. We would do well to look at shrouds
> on both sides of the radiator and a plate across the frame to keep
> the turbulent air from coming up from the road disturbing air flow
> into the radiator. This summer on a trip back from Colorado I used a
> 16 inch electric fan in front of the radiator when the fan clutch
> went out. Worked good even with a 4000 pound towd on the back.
> Ambiant temperatures were in the high 90's. My plan is to look into
> this a lot farther. Really tired of changing fan clutches. And yes, I
> have changed the clutch out the top without removing the shroud. I
> have the bloody knuckles to prove it...........Terry
>
>
>
> _______________________________________________ GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61481 is a reply to message #61406] |
Sat, 24 October 2009 16:24 |
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The fans from ford that would make the most sense for use on our coaches would be the ones found in the mid 90's Tarus SHO and the Lincoln Mk VIII those are huge, around 20" IIRC for the lincoln and dual "15 for the SHO and move alot of air, they are also dual speed, and can be easily wired up to be controlled by an aftermarket fan controller. both units are available at most "mens Malls" across the USA, and on eBay. Make sure you take the wiring pigtail fromth donor vehicle as that will help with setting up the aftermarket controller.
Another fan combo to look at is this one, it flows 5500 CFM! http://www.flex-a-lite.com/auto/html/monster-electric.html
Also the first and formost modification before adding an electric fan setup is to address our dismal 80 amp alternators, they will just not get the job done on a hot day, and you will wind up sapping your battery with an electric fan. for this I recommend going here...
http://www.paperformance.com/scripts/prodView.asp?idproduct=71
and picking up one of thsoe 200+ amp beasts which will keep the headlights, battery and fans happy. at idle they make over 100 amps, more then our stocker units make at full curise! PA alts are all new and have a LLW, not rebuilt stuff, you will need likely to have a V belt pulley installed unless you go to a serpentine belt. PA can set that up. they do alot of stuff for us Ford guys, and now have alot of nice GM stuff too...
| hertfordnc wrote on Fri, 23 October 2009 22:32 |
There was a big discussion on this on the revcon board and the consensus was that it was not viable. But I think we might suffer from intelectual incest. We give the most credit to people with GMC/REVCON expertise. But really, it's just an engine and a radiator. Maybe someone else knows more about it than we do.
So I poked around the net and found that the offraod crowd uses electric fans on big blocks moving at very slow speed under pretty serious load.
They say to use a fan off a Tauris or a Lincoln. Not sure what years.
I don't claim any expertise here myself. Maybe an RV is different. But the Car industry keeps putting electric fans on bigger and bigger vehicles, they must know something.
|
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
[Updated on: Sat, 24 October 2009 17:06] Report message to a moderator |
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| Re: [GMCnet] ELECTRIC RADIATOR FANS [message #61550 is a reply to message #61438] |
Sun, 25 October 2009 09:46 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Terry Skinner wrote on Sat, 24 October 2009 10:51 |
I think the biggest problem the GMC has is the distance between the fan and the radiator. Back in the days when we did a lot of engine conversions we tried to get the fan as close to the radiator as possible.
The shroud on the GMC is a bandage on the problem. If you look at the newer race cars they devote a lot of effort into ducting air into the radiator, not out.
We would do well to look at shrouds on both sides of the radiator and a plate across the frame to keep the turbulent air from coming up from the road disturbing air flow into the radiator.
This summer on a trip back from Colorado I used a 16 inch electric fan in front of the radiator when the fan clutch went out. Worked good even with a 4000 pound towd on the back. Ambient temperatures were in the high 90's. My plan is to look into this a lot farther. Really tired of changing fan clutches. And yes, I have changed the clutch out the top without removing the shroud. I have the bloody knuckles to prove it...........Terry
The attached quote is from Dave Silva,
> hertfordnc wrote on Fri, 23 October 2009 23:32
>> <snip>
>> I don't claim any expertise here myself. Maybe an RV is different. But the Car industry keeps putting electric fans on bigger and bigger vehicles, they must know something.
Terry Skinner
|
Terry,
You have an interesting collection of experiences here, but your conclusions have some minor flaws.
Are you still running with just the 16" electric fan?
Do you remember the Manufacturer and Model?
I contend that the GMC fan shroud is not just a bandage on the problem, but was probably seen as an adequate fix at that time. While it may be unfortunate that they did not finish the job, that is the level of engineering is what would I expect for that period.
In deed, with the addition of some forward baffling and an air dam underneath to use the under-vehicle depression I would expect that need for a fan on the could be greatly reduced. Many steam powered naval vessels used "scoop induction" to provide cooling water for the main unit condenser. In studies we did as undergrad (on contract) we used the primordial computers of the day to prove that they were getting as much of the water flow from the downstream depression as from the intake ram effect. Unfortunately, to be effective, these features cost as much horsepower as the pump that they were supposed to replace, and they still had to have a main circulator for operation at less than cruise.
The racecars that are built to purpose (eliminating NASCAR and other "stock" types) actually pay every bit as much attention to the outlet side of the coolers as they do the intake side. It may not look that way because you can only easily see the intake with the vehicle assembled. And Remember - They do not expect to need much cooling when they are at less than flat out.
The fan shrouds came into popularity with the vehicles that were optioned as I-6 or V-8. The later being 2 cylinders shorter from RFB(Rear Face of Block), the manufactures first moved the radiator into the engine space and then added the shroud. It was quickly discovered that, what us marine engineers knew about, Kort nozzles and thrust rings applied here also (see Tin Gerbil and Gray Casey). The distance from the rear surface of the heat exchanger to the leading edge of the fan actually helps the system distribute the air flow through the heat exchanger more uniformly, and this is and advantage. This also worked out well as emissions rules were causing the engine space temperatures to rise and highways speeds and loads were causing over heating issues that were not seen previously.
The fact that some do hear the fan engage at road speed does indicate that there is something that is less then optimal, but without a very complete study, I would not venture to say what it is with any confidence. If someone would grub-steak the operation, I would be glad to build a model (mathematical) and do a complete CFD(Computational Fluid Dynamics) study of the air flow in the GMC engine space. It can probably be completed for just the cost of a few nice coaches.
Unfortunately (sort of.), I do not have an ASHRE tunnel at my disposal these days, it would be neat to know what the GMC radiator-shroud-fan set is actually doing. Then any case for a replacement could be evaluated with real data.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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