Having read what everyone has said, I have come to the following conclusions for me, and hope this helps others:

1) Sender belongs in the radiator, because mainly of fan runon after engine shutoff(stop heat soak of aluminum engines and heads, and not have to complicate temp sender). Thermostat will open wide at engine shutoff and convection will circulate coolant.

2) The fan or fans need to be at least 2-3" away from radiator surface to allow air to escape out of fan holes. Needed to eliminate air pileup between radiator and fan/thin shroud mounted directly on radiator. This problem occurs when driving, and fans would be off. At idle this air pileup would be sucked away by fans. Another option would be "flaps" in the area around fan/fans. This is an especially acute problem because radiator is at an angle to air flow.

3)fans need to be angled to blow over engine, and scavenge engine compartment heat. This also works well with 2), and helps cool passenger compartment. I think if two fans are placed at the top of an angled shroud, it would clear all of the suspension junk nicely.

4) A higher output alternator is required for the 30-40 amps used when fans are running. I would say 105 amp minimum.

5) A two step speed control is desirable, mainly because of fan running after engine is off, and energy required. Also staging would reduce the electric spike when fan turns on, and when it turns off.

6) AC control would run fan at low, or turn on one fan of dual system.

7) Turnon temp of sender would be in the 205-215 degree region with a 195 degree thermostat. This has the most subjective or maybe scientific setpoint.

SHIELDS ARE UP!!

 

This person hasn't got a clue on how to keep an internal combustion vehicle's engine cool.

This is probably the BEST list of what NOT to do to your car's cooling system that I have ever seen....

COMPLETELY wrong.

EDIT: well, except the bit about the alternator...

 

Your pretty hard on him. Saying you are COMPLETLEY WRONG and then leaving it is not right.

This is how I keep my bigblock in the 180 range.
I have a big tube 1 1/2 tube 2 row alluminum rad.
I run 2 16 inch tornado fans, one low and behind and one high and in front.
I sped the water pump up 30% by putting a small pulley on the water pump.
Finally after alot of testing a motor runs cooler without a thermostat and NO restrictor.
The small spoiler under the front end also makes a big difference.
My motor also runs cooler with the light off and down.

With this setup I never see 200 and most of the time on the highway drive without any fan turned on. The motor stabalizes around 185 degrees with no fan on the open road and a few miles from home I turn both fans on and bring the temperature into the 170 range before shutting down to prevent heat spiking when turning the motor off.

 

His last statement of sheilds are up kind of leads me to beleive this is a trick statement. Most of what he said is not correct. Not going to comment on this.

 

Which is why OEM's put the temp sensor in the cylinder head because they know nothing. My fan's don't run on because the relays shut off when the ignition is off. No problems with heat soak.

Nope, if you do this, when the fans run they will suck air around the shroud instead of through the radiator. My Spals have flaps but even if they didn't, there is enough room for air to flow between the fan blades. Look at OEM and good quality aftermarket installs like DeWitt's.

Nope. Passenger compartment is not coole by the engine fans. Those would have to be pretty small fans if you want them above the suspension.


I run an 80 amp. 105 might be better.

My spikes are reduced by having the relays control the power and sourcing it from the battery. No issues so far.

OK.

I have a 195 on, 185 off switch with a 180 thermostat. Runs right at 180 on the highway and cycles in town. Works for me.

 

This is not a trick statement, and based on an engineering background, is what I feel is required. All I'm saying is that it's alright to attempt to shoot holes in what I said; but at least explain why you disagree. I'm trying to pick everyone's brain on this subject.

I don't know why a higher output waterpump would help unless there are corners in the block where coolant has a chance to almost stop, and create a hot spot. Circulating the coolant faster(assuming the radiator is doing it's job) should have little effect. You will get slightly warmer coolant into the radiator but it shouldn't have that big of an impact.

Jim

 

Where did you get this information? This issue has been discussed to death on this forum and the results of all the members actual findings are opposite to the items you have listed except for a couple. If you would do a search on this subject you will find what most us have found to be true.
You do need a strong alternator to run multiple fans, but my stock alternator has not had a problem keeping up. I do have my fan thermostat located in the radiator but a better location would be in the block or intake. Everything else seems to bee from outer space and we have never seen any of it in print.
Don't mean to be upset, just would like to know your source of information.
Bernie

 

jbs75 - Go ahead and try your theories out on your car then post the results. I would be curious to see how long it took you to overheat.

 

you're gunna LIKE IT MISTER!!!

 

I have to disagree. I have seen tons of pics of engines with fans mounted as close to thier rads as possible. Check out the websites of Flex-a-lite or SPAL and you will see the fans they sell bolt right against the rad.

Try to think of it like this - the rad cools the engine and the fan cools the rad. The fan doesn't cool the engine.

Depends on if you have other electrical loads like a big stereo. I wouldn't say required but definetely desireable.

Sure. I like the setup of a lot of European cars. Low speed is two fans in series, high speed is two fans in parallel.

Probably not necessary, just control the fan based on engine or rad temp.

You bring up a lot of interesting things to think about there jbs75.

 

There just ain't enough popcorn for this thread... :

 

I already have(on a volvo P1800); 15 yrs ago and works great, just like it should.

All of the vehicles I have seen in the last 15 yrs. have had fan control sending units in the radiator from the factory. Now mind you this is for radiator fan control ONLY. Fuel injection must be in the block for at least one of the senders, and of course the dash temp guage has to be there too.

Now that I think about it; probably the switch to after engine shutoff fan operation probably occurred with the switch to 195 degree thermostat.

 

You haven't seen ANY Corvettes with a fan switch in the radiator, have you?...Case closed.

 

Although I'm not strongly committed to this and feel it largely is irrelevant provided it's not too far removed from engine coolant heat, I think all sensing should be best done at the device concerned with being monitored - the engine itself, not the heat exchanger.

Absolutely and completely wrong. This will waste easily the majority of the fan energy. It is vital the fan pull straight through and not around the radiator. Many have addressed this clearly - you're just being stubborn here!

"...and here we see the root of our subject's obsession... " So many have assumed this is a real event with no data to support it.

I challenge this even OCCURS!

Again, many have noted, clearly, e-fans freewheel or speed up when hit with increased pressure. Having thin blades and lightweight rotating assys (unlike mechanical fans) they don't take much to spin, have minimal resistance to air flow in the first place and can spin at any speed. Off, they won't eat that much air flow to freewheel; on, they will have only increase the velocity of air going through, even if it's already moving.

Now, if you just mean air piling up in a full sealed shroud, we agree. Lightweight vents, flaps or no shroud at all (and not relying on shroud "vacuum" for fan action) is needed for this.

Wrong again. The impact of any actual resistance to flow created by after radiator fans and shrouds has nothing to do with radiator angle. Radiator angle does have somethign to do with minimizing velocity of incoming air the car runs through.

No such need. This heat build up thing keeps you up at night, doesn't it? One of your ancestors was a designer at VW, wasn't he?


Now I am the idiot who likes a 250 amp welder alternator type thing, but really, 60-80 amps is enough for just fans, lights and blower motor. Start adding stereo components, electric fuel pumps, electric water pumps, neon tubes (you're going to put some on yours, aren't you...AREN'T YOU?!??! ) and add in a weakened wire here and there and a battery half through it's life and, then, yeah, go for more!

No challenge. I have two switches for three fans. Control is neat as long as it's reliable (and readily bypassable when it fails.)

Again, no challenge, but I'm not sure this is of any great concern. The battery serves as a pretty big electrical spring. Regular turning signals probably cause a bigger "twitch" to stereo, ignition and lights.

"Now you're just being MEAN!!!" You KNOW I don't have A/C!!!

No real argument - provided there is not a heating problem it could be higher or lower, as long as you have a ways till BP.

Possibly - then again, possibly not. Why go to all the problem of maximizing all other components of the cooling system just to minimize the wp? More flow is not going to hurt anything except waste some power, but below a point it would remove less heat than could be removed. Plus, as you allude to, enough extra flow may get more frequent coverage to more "corners" - maybe even more to the crucial deficient areas of SBC cooling - the heads.



"Sir, she's bypassed like a #(%*in' Christmas tree! She canna take no more direct hits lad!"

 

i run one 16" perma-cool fan mounted right to the rad and no shroud and power it with with two relays. one turn's on the fan when the car is running and make's it run all the time, the other turn's on the fan by the temp switch and keeps the fan running for about 4 to 5 min. after i turn off the motor. i have let it sit and idle for a long time while tuning on it. has'nt ran hot yet. just running around town it never moves off 180. hit the hwy and it drops to 170. (the pace car spoiler helped this i think) and i have a 15 amp fuse in line for power so there's no way it can pull 30 to 40 amp's, it will blow the fuse first, and i've had no problems with it.

 

There is german in me but it goes faaaar back. Course there could be some VW blood in me, but I was never partial to german cars.

Clarifying the air dam situation; I assumed a combined fan/shroud. The ones I have seen are very thin.

If you didn't have a thermostat, you would need a temp sender in the block to take the place of the thermostat plus some additional junk(like an electric water pump/controller). But you would still have a temp sender in the radiator to control some radiator fans.

A single fan with no shroud should be a problem with overheating. I had tried that years ago but the air never left the engine compartment. Adding a shroud and sealing all the extra holes in the sheet metal around the radiator fixed that.

 

Why would anyone want to make their cooling sytem this complicated. I have a 14" and a 12" fan mounted on an aluminum shroud I fabricated. I use the painless wiring kit wit the temp sending unit in the block. the simpler you keep things the less likely they are to fail.

 

EXACTLY,

thats why i stick with the stock mechanical fan and shroud. No wiring mess and wimpy electric fans to try and cool the engine.

 

and, most importantly, they don't slow down either with lack of engine rpm OR with increase in engine rpm past 3K. Although I would love to get some NUMBERS on mechanical fans...it took long enough to find some on mechanical water pumps....and I can see why they hide those....

BTW, mine cools much, much better with my e-fan setup than it did with the mech fans. These are not the e-fans of the early '80's - they really move some air.

Yeah, I would agree a single, medium flow, medium flow fan with no shroud would be very ineffective. It's one key reason I went with three instead of two - more area coverage and I really was concerned about shrouds blocking flow. Therefore I wanted to completely do away with the shroud to allow air flow through the remaining 32% not covered by fans. I honestly had never considered the clever one-way shroud flaps on the SPAL/DeWitt setup....hadn't seen them in person. Ideally I would like some pusher fans, but there is only 1.75" room max between the radiator and the condensor and only room for 2 5" - maybe 7" tops fans in front of that.

As to complexity....mine is anything but complex, and, that which ALL the dinos like DJ (who hasn't bit yet! ) have missed in the e-fan vs. mech fan controversy is the strength of not just a mechanical fan setup, but a flexfan with no clutch - simplicity and reliability of operation.

Mine is three fans, two switches, two relays. I have no thermostatic control. I don't even have a thermostat but a restrictor plate.

I consider the trade of an inherently less reliable electric system somewhat traded off by both the increase in cooling performance and the removal of so much vibration and stress from the water pump bearings.

 

if you think 12 volt electric motors are the *****, try a 12 volt supercharger.

nouf said.

no electric fan is going to move as much air as a engine driven fan.