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Two Cents on Electric Fans

Started by lalessi1, 2017-11-05 09:41

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lalessi1

A lot late with my two cents on the previous post .... I agree that 200+/- degrees is not too hot but it does indicate a lack of cooling capacity. In my mind the thermostat should dictate the system temperature. It has been my experience that old (our) cars run better cooler than warmer. A 160 degree thermostat is preferable to a 180 in my opinion. I believe that electric fans are better than mechanical fans simply because that can move a lot of air at idle and do not consume more power at speed. Electric fans are used in virtually every new car because they are more efficient and can be better designed as a separate element and matched to demand. They can be a little harder to adapt to an older car than one might think (more on that in the next paragraph). A mechanical fan shroud is a better solution for most circumstances.   

I really wanted to share my latest cooling system issues. I have an FE engine that is producing a LOT of heat. My 18" 7 blade Flex-a-lite fan was not moving enough air at idle to stop the coolant temp from creeping up at 90+ ambient temps. I have a Griffin aluminum radiator. I was designing a shroud for a local sheet metal fab shop to build for me when I decided to switch to an electric fan (especially for my A/C project also in the works). I bought a Derale 17" fan/shroud assembly (16822). I had to move the radiator forward 2" to clear the added A/C drive and the electric fan. Once completed my car will idle at 170-180 with no issues. HOWEVER, I drove the car for 200 miles and I noticed the temp would start creeping past 205 degrees at 75 mph when behind an 18 wheeler! Apparently the fan shroud is restricting air flow through the radiator at highway speeds. I contacted Derale and they agreed that could be my issue. They are sending me  a set of rubber flaps that when installed over added holes in the fan shroud will act as "check valves". FYI
Lynn

hiball3985

My friend is going through a similar problem since installing an electric fan on his 55 Bird, above 65-70 mph it starts to over heat. He is adding the flaps and holes so we will see if that helps. The fan he has is mounted in the middle of a lot of sheet metal that blocks air flow, looks like a dump design to me.
When we built a 302 for my sons 66 mustang he added a so called HI performance fan blade, it over heated in traffic, he then tried two other brands of the HIPO flex fans, same problem. Put the stock fan back on and never had another problem.
JIM:
HAPPY HOUR FOR ME IS A GOOD NAP
The universe is made up of electrons, protons, neutrons and morons.
1957 Ranchero
1960 F100 Panel
1966 Mustang

lalessi1

The stock fan I had was a 4 blade.... The design of the Derale is similar to the "dump" (typo????) design you mentioned. At least I am not imagining the issue on the highway. The fan shroud I designed would have been similar to the Derale design, not room for much else. The problem is not huge, I think spacing the shroud away from the radiator could work too. I do have a '70s vintage Ford flex fan but I think the model I have was recalled for fatigue failure. I really do appreciate your input.
Lynn

chapingo17


John Palmer

#4
I think if you take one look under the hood of any modern vehicle you will come to the conclusion that there's very little room to package an old style mechanical fan and a shroud behind the radiator.  Compound the fact that many engines are transverse mounted for front wheel drive, and have radiators that are front mounted.  Using a electric motor to power the fan in a modern vehicle is just a simple way to get around other problems.  I'm sure the engineers will also bring up possible fuel savings, and the need for consistent high engine temperature for emission reasons as to why they made the changes.

Air flow has to be looked at from several views.  It cannot flow through a (aftermarket thick core) if it cannot flow out of it due to air flow restrictions.  Look for possible restrictions in front of the core, look at the core and check it for air flow by placing it in front of a wall fan and feel for how the air flows through it.  If everything is OK up to this point, you need to add some one way flapper's to let out "high speed positive air pressure" from the shroud.  They need to be there so they can seal the shroud during "stopped" of slow speed driving when you might have "negative air pressure" inside the shroud.

Any sized FE engine should have no problem running cool with a stock core radiator and a mechanical fan if everything is within spec.  Make sure you do not have more than 36 degrees of "initial, and centrifugal" timing.  It's two different settings, that need to work in concert.  Shoot for 10-12 initial at the crank, plus 10-12 degrees centrifugal in the distributor, and you will have 30 to 36 total, under road load driving.  Note the vacuum advance timing is in addition to this, but only effects "light load" (high vacuum) driving.

Make sure your using a digital temperature gun and not some line on a 60 year old gauge to make your temperature comparisons.  If it's not puking some water, it's not hot!  Most of us "over fill" the coolant, then get concerned that we are loosing some coolant.  When these cars were new, we did not have overflow tanks that caught and recycled the lost coolant.  The top tank was the reserve back in the good ole days, but you only filled it to the round hole inside the tank baffle, not to the bottom of the cap.

gasman826

If I remember correctly, your FE is quite beastly.  Stock components may be taxed beyond their capabilities.  A thermostat regulates the engine temperature.  Engine temperature shouldn't exceed the thermostat opening temperature by more than thirty degrees...idling, WOT, AC on, or cruising.  Is the electric fan a puller or pusher?  Does it have a shroud?  Is the alternator big enough to support fan and AC?  Like already said, confirm the temperature with another device...another gauge, high tech point and shoot, my favorite has been a cooking thermometer.

Everyone's setup is different.  I have a cheap-o, eBay special, bolt-in aluminum radiator with trans cooling circuit cooling a basically stock block 351w roller, Ford Racing aluminum heads, Stealth intake, Comp Cams Mutha Thumpr hydraulic roller.  There was not room for a mechanical or electric fan/shroud between the radiator and pulleys.  Since this is the Raunch Wagon and wrecking yard parts are best, I had a Mark VII fan hanging on the wall.  I bench tested and nearly created a drone.  This thing moves a lot of air.  It is installed as a pusher (less efficient) and has a shroud (even less efficient).  With a 165 degree engine thermostat, the fan cycles on the hottest days at idle.  The fan is on at 185 and off at 180.  The fan only cycles at long lights and some in slow traffic.  Does not run at WOT or cruising.


JimNolan

My take: A thermostat will control how cold your engine gets, not how hot. Your cooling capacity and the amount of air flowing thru the radiator will decide how hot your engine gets. After electric fans, fan shrouds and a 3 core radiator with 1/2" tubes, I still couldn't get my heat down. Finally went to a Griffin 2 row 1 1/4" tube radiator and set a 6 blade fan 1/2" from the radiator face. FlexFan was who told me how far to set the fan from the radiator. I didn't use their fan though, I don't want anything flexing up there.
If there are no dogs in Heaven, then when I die I want to go where they went.

hiball3985

"dump" (typo????) OOOOPs, sometimes I walk a fine line between typing and brain farts  :003:

I should have mentioned that the problem my friends Bird was having was over heating in parades and stop and go traffic, a common problem with Birds from what I have been told. After trying several of the 101 fixes people recommended, different pumps, pulley sizes, thermostats, radiators, fan blades etc etc he finally solved the problem at low speed with a 2 row radiator and electric fan but now it heats on the freeway. I always felt it was an air flow/restriction problem so I'm still waiting on the flap instillation to see if that helps.
JIM:
HAPPY HOUR FOR ME IS A GOOD NAP
The universe is made up of electrons, protons, neutrons and morons.
1957 Ranchero
1960 F100 Panel
1966 Mustang

lalessi1

#8
Thanks guys for the comments and input. My fan is a 17" Derale with shroud, it is a puller. My gauge is a 2 5/8" mechanical Stewart Warner. I have not set the fan temp control feature at this point although I have the probe installed in the radiator. The fan kicks on at 140, the low default. The engine is 462 cubic inches with 11.2 static compression ratio, it dyno'd at 501 HP at 5400 RPM. I am running a 3.89 rear end with 28" tires, the speedo is dead on, 3270 RPM @ 70 MPH. The highest temp I saw was 205 but it was climbing until I hit "clean" air. I still believe a car should run at the thermostat temp if it has adequate cooling. I do agree that 205 is not "hot" but my engine runs MUCH better at 160. I think my fuel was on the verge of boiling in the carb as the car started to hiccup at about 190. I am planning on a larger rerouted fuel line, a carb heat insulator, an oil cooler and the flaps. I have a 75 amp alternator so I think that will work with the fan and A/C? My ignition timing is 10 initial, 24 centrifugal (all in around 3500), and 7 vacuum. I am still playing with the timing.

Jim, you had me wondering what a "dump" design was for a few minutes!  :003:   
Lynn

hiball3985

Lynn, that fan shroud looks similar to the one on my friends Bird. I'm no aero engineer but they just look too air flow restrictive to me for higher speed driving. It would be interesting to calculate how much area the sheet metal covers vs the size of the opening and what percentage it is..
JIM:
HAPPY HOUR FOR ME IS A GOOD NAP
The universe is made up of electrons, protons, neutrons and morons.
1957 Ranchero
1960 F100 Panel
1966 Mustang

JimNolan

lalessi1,
You are in a whole different area code with 500 hp and cruising at 3200 rpm. It wouldn't hurt you at all to contact FlexFan, Griffin, etc. for support and suggestions. That's a lot of BTU to get rid of. A FlexFan engineer was the one that recommended I put my fan closer to the radiator. These guys experiment with all sorts of cooling problems. And, you seem like you are close now, maybe just a little tweeking is needed. I run under 400 hp on my engines and all I just use is a radiator and 6 blade fans on every engine I got. One of them even has a A/C condenser in front of it also. Good luck
If there are no dogs in Heaven, then when I die I want to go where they went.

rmk57

3200 rpm is a lot of rpm for sustained highway driving. Have you experimented with different pulley diameters to try and slow down the water pump and give the radiator a chance to cool properly.
Randy

1957 Ford Custom
1970 Boss 429

lalessi1

I failed to mention that I am planning to change the rear gear to 3.25. That will drop the RPM to 2730 @ 70 MPH. I can't really change the pulley easily, it is a double 8V serpentine one that is as small as will clear the water pump. It is roughly 1 to 1 with the crank pulley already.

I calculated that the shroud opening is roughly 50% of the total shroud area. The velocity of the air through the radiator at idle is roughly 10 MPH. The shape of the shroud allows the assembly to be as thin as possible. Flex-a-lite makes a better design IMO but is almost 2" thicker, room I don't have as currently configured.
Lynn

hiball3985

When you consider how many different problems can cause heating it can drive you crazy. I don't think fan design has any effect on the problem at speed, fans were required for stop and go driving conditions. No race cars that run at speed use fans.. I think this was also the thinking when they designed fan clutches, no reason for the fan at speed because air flow is more than a fan can pull.
I think with 50% less surface area it's a flow restriction, maybe it causes a high pressure area between the radiator and shroud? I haven't seen what the rubber flappers look like but I would use as many as possible. So thats my 2 cents  :006:
JIM:
HAPPY HOUR FOR ME IS A GOOD NAP
The universe is made up of electrons, protons, neutrons and morons.
1957 Ranchero
1960 F100 Panel
1966 Mustang

John Palmer

I agree with Randy that the 3200 "sustained" RPM is high, and it will produce more BTU's to remove, adding to the highway cooling issue.  The gear change should help.

Regarding the thermostat........In addition to controlling the engine warm up, and cold weather engine operating temperature, it also controls the flow of the coolant at full temperature.  It provides the coolant flow restriction that allows the coolant to stay in the radiator long enough for the cooling air flow to absorb the engine heat.  It's the reason they sell various sized hole restrictor plates for racing engines that do not run a normal temperature controlled thermostat.

The pictured shroud looks to me to be very restricted as to air flow for a highway application.  I would try a rubber flapper in every possible flat surface to let out any "positive air pressure" during high speed operation.

Have you tried to "pop the hood" up to the safety latch, and doing your highway driving test?  My thought would be to confirm (or not) that you really are fighting an air flow problem.  Popping the hood would increase the negative pressure in the engine compartment and I think it would increase the air flow across the radiator even with any possible restrictions.  It might just be another "cheap and easy" diagnostic tool to try? 

Things like this are "Very Frustrating".  I fought one similar on my former '32 high boy roadster with a SBC.  It ran cool on the highway, but boiled at low speed.  After much work and cussing, it turned out to be a "off shore" crappy aluminum water pump.  The impeller had about a 1/2" clearance to the casting body, and had no coolant flow at low speed.