Is switching from mechanical to electric fan a good idea?

Boss 351 · Feb 10, 2006

I did this last night and I'm not sure if I see any real difference in HP, of course I didn't test it since the drag strips are closed for the winter and the street I do my "testing" on (you know, floor it from one spot to the other and see how fast you're going once you hit a marker) has traffic now due to a detour so it isn't a good time to go 3x the speed limit going up a hill lol

Plus I had some problems trying to find a friggen 40amp (or more) relay and fuse around here, all I can find are 30amp which isn't enough. It does clean up the engine bay though, I can see the front end of my engine now.

5.0 con-vert · Feb 10, 2006

I did this as soon as I got my car. I don't regret it whatsoever. I think I felt a small increase in the SOTP but only when the clutch really engages can you feel the parasitic drag. As you said, it definitely cleans up the place a bit. Did you get a sticker with it? Thats where the real horsepower is!

Michael Yount · Feb 10, 2006

If you really want to take advantage of the electric fan's potential, and minimize wear/tear on the fan/alt/battery/electrical system, you should use one of these to control it -- www.dccontrol.com . Those of us that have them will never use relays again.

A properly working clutched-mech. fan probably consumes on the order of 5-10 HP at higher rpms. Even the biggest electrical fans only consume 1-1.5HP when they're running full speed -- most less than 1HP. And of course -- ZERO HP when they're not on. So that should give you an idea of the potential gains available with the switch to an electric.

393Bird · Feb 10, 2006

There is a reduction of power robing drag, so it will free up some power. Just as important, is improved cooling. Under normal weather, if you have a decent sized radiator and not using the A/C, you do not need a fan at highway speeds. The biggest cooling problem is in slow moving traffic. This is where the electric fan kicks butt. I have a built 393, 3500 rpm stall speed and non lockup Lentech, and 4.30 gears. I am using a Mark VIII fan, and have never seen the temp gauge above 190f, even while driving in the 4th of July Parade. A properly sized electric fan will make the car a pleasure to drive in any temperature.

Boss 351 · Feb 10, 2006

Hi, thanks for the tips. I sent out quotes for this thing here:
View attachment 487834
It's also a variable controller and easy to setup from what I read on the website. Plus I can use factory sensors with this thing.

795.0pacecar · Feb 10, 2006

I have the spal fan controller. Its awesome. I think it is easier to set up than the DCController. I got my SPAL controller for $70 on ebay and a nice thing about the controller is you can just tap into your water temp gauge sending unit wireing instead of using a radiator probe.

Boss 351 · Feb 10, 2006

I just ordered it from 2Koolperformance.ca. I like how you just have to push a button to program low and high settings. More gadgety things on my car lol I should have it next week. Now I just need a 50 amp relay so I wont fry my 30amp unit. Oh and to get a stronger alternator sine I'm putting a pretty good load on the system. (I have the same alternator as a 95 Mustang).

795.0pacecar · Feb 10, 2006

What kind of fan are you using. My fan at the most draws 18 amps on high speed startup, making 30 amps plenty.

Boss 351 · Feb 10, 2006

I got a stock 4.6L fan from a 97 Mustang? On the high setting, it killed a 30 amp fuse and the fuse housing, maybe I had a bad fuse. I do have the means to measure the amperage draw, so I'll check it out before upgrading relays and going with higher guage wires (14ga right now).

sgarlic · Feb 10, 2006

So with this Spal controller, you still have to use fuses? That's weak.

Boss 351 · Feb 10, 2006

Well fuses are needed for anything... you don't need a relay though, I only want a larger relay for the time-being. I don't want to set my car on fire, not yet anyway lol

HISSIN50 · Feb 10, 2006

That was something I wondered too (in regard to SGarlic's post) - buying relays adds to the cost and probably comes out near Baskin's controller price.......
Sgarlic knows which way I would go.

baskin · Feb 10, 2006

Actually I don't think the spal is variable speed, I think it's just two speed They also recommend an external relay for their 34A dual fan setup, so the current capability isn't that high.

With regard to the temp setup, it's pretty nifty, but what happens when your battery goes dead? Is that really a time when you want to be re-setting up your controller? I'd rather spend the extra 5 minutes in a nice warm garage setting up jumpers than 20 minutes on the side of the street after getting the car started.

With regard to tapping into the water temp gauge, what use is the gauge now? If things go south, your fan may be turning on at 250 degrees while you're comforted by your gauge, which is reading 180, so both your control and monitering fail at the same time. Redundancy is a good thing.

timewarped1972 · Feb 10, 2006

question about wiring these controllers.

i don't know about the spal unit, but according to the dcc you basically wire it straight to the battery, or you can wire the positive to the starter selenoid with a special wire you can purchase.......

question: where or how do you wire these things if you only want the fan to run when the key is on?? is there an exisitng switched 12 volt circuit you can wire the positive lead to? or, do you need a 12 volt switched relay that when the key is on, the relay is activated and you'd put that relay in between the battery and controller positive wire??

baskin · Feb 10, 2006

Boss 351 said:
Well fuses are needed for anything... you don't need a relay though, I only want a larger relay for the time-being. I don't want to set my car on fire, not yet anyway lol

It takes about 3 uS to destroy an active device, so a fuse will prevent a fire for a dead short, but any other condition, it’s pretty much useless. For instance, if the armature on the fan shorts out, which is how most motors die, the current on low speed will more than double. It won’t blow the fuse, it’ll just cause the unit to go into thermal runaway, and that’s never a good thing. The only way to do it right is to monitor the load at every pulse and monitor the temperature of the control unit. It’s more expensive, but it’s the correct way to do it.

baskin · Feb 10, 2006

timewarped1972 said:
question about wiring these controllers.

i don't know about the spal unit, but according to the dcc you basically wire it straight to the battery, or you can wire the positive to the starter selenoid with a special wire you can purchase.......

question: where or how do you wire these things if you only want the fan to run when the key is on?? is there an exisitng switched 12 volt circuit you can wire the positive lead to? or, do you need a 12 volt switched relay that when the key is on, the relay is activated and you'd put that relay in between the battery and controller positive wire??

There's a low current input to control whether or not it continues to run after the car is off. It doesn;t cycle on and off like relay though, it will just ramp down over about 15 seconds, so most people don't switch it with the ignition

795.0pacecar · Feb 10, 2006

baskin said:
Actually I don't think the spal is variable speed, I think it's just two speed They also recommend an external relay for their 34A dual fan setup, so the current capability isn't that high.

With regard to the temp setup, it's pretty nifty, but what happens when your battery goes dead? Is that really a time when you want to be re-setting up your controller? I'd rather spend the extra 5 minutes in a nice warm garage setting up jumpers than 20 minutes on the side of the street after getting the car started.

With regard to tapping into the water temp gauge, what use is the gauge now? If things go south, your fan may be turning on at 250 degrees while you're comforted by your gauge, which is reading 180, so both your control and monitering fail at the same time. Redundancy is a good thing.

I had to unplug mine to rerout some wires better and it held its temp setting memory. If the water temp sending unit goes bad then yes the fan wouldn't function properly, your gauge has nothing to do with it, and I have an aftermarket gauge anyway so I know what temp I have it switching on and off at, I also dont have the SPAL tapped into the gauge wiring, I have it going directly to the sending unit. The radiator probe on the DCController could go bad just as easily after vibration causes the radiator fins to cut through the wire insulation and ground out the probe, so that argument about failure goes both ways.

The amp capacity of the unit is 30 amps, if you have dual fans you have to run the secondary off a relay.

Im not trying to start a pissing contest, they are both very good ways to control the fan, both have their strengths and weaknesses.

baskin · Feb 10, 2006

It uses a binary counter to set the temperature. I looked at doing it that way myself since it’s cheaper than the jumpers. Depending on the input filter, it might hold the setting for a couple of minutes, but it’s not going to hold it long enough for you to buy and install a battery.

If it’s hooked to a sensor separate from the gauge, you have a point. If it’s on the same sensor, you don’t. It’s pretty rare to see a DCC sensor or any other piece go bad, in fact on the few that I’ve seen, the wires were pulled out of the connector end, I’ve never seen a sensor that was actually bad. It’s housed in brass, then covered in neoprene, so shorting the wires is all but impossible Reading the temperature independent of the gauge is just common sense, that’s why it’s usually done that way. Reading from the sending unit is used to cut costs.

Most of the decent fans (Mark8, Taurus, SN95) draw 35-40A If you want to do it correctly with these fans, you’ll need a 75A relay (22.00), a separate sensor (15.00) and the controller. You’ll still have a two speed setup, in spite of the variable speed nomenclature, it’ll still need reprogramming if your battery dies, and it will still fail, in spite of the fuse, if the output or fan shorts out.

I'm not saying it's a terrible choice, I just think the DCC is a better thought out solution. Most people choose the DCC for the variable speed, but my car is worth a lot more than the controller, so if I was making a choice to buy either one, and for obvious reasons I wasn't, then I would spend the extra few bucks for the short circuit, overtemperature, self extinguishing epoxy, and firewall protection without even considering the variable speed. It's not just what you see and use every day that's worth the extra money. Some of the more important things are what you don't see and hopefully never need to use.

superhuaman · Feb 11, 2006

For mine I had to special order a 70A relay for about $15 after going through 2 30A relays. Im using a Volvo 380 twin turbo fan and it works awesome. The relay is still a Bosch relay, however the load terminals are 3/8" tabs instead of 1/4" like they usually are.
http://i11.photobucket.com/albums/a172/superhuaman/coil.jpg
http://i11.photobucket.com/albums/a172/superhuaman/radfan.jpg

EDIT:
I seem to have lost the picture of the relay. argh. but you can see the 60A maxifuse, with holder.

Is switching from mechanical to electric fan a good idea?

Boss 351

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