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The mkiv Supra Owners Club

Twin Electric Fans


Supra ST Myster

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You want them on a thermostat. The viscous fan is not on all the time, that's the point, it only locks up when it needs to. You don't want the fans on when you have enough air flowing through the rad anyway or they'll get in the way of that air, and it's a waste of power having them on when the temps are low.

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You want them on a thermostat. The viscous fan is not on all the time, that's the point, it only locks up when it needs to. You don't want the fans on when you have enough air flowing through the rad anyway or they'll get in the way of that air, and it's a waste of power having them on when the temps are low.

 

Oh i didnt know that about the viscous fan,!! do you think the viscious fan is using more power to run over the twin electric ones?

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Oh i didnt know that about the viscous fan,!! do you think the viscious fan is using more power to run over the twin electric ones?

 

Probably not. It's directly connected whereas the electric ones have to turn the alternator to produce electricity (which loses some power) and then turn the motors to produce movement again (which loses some more).

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If you go with the above, or any Fan controller for that matter, make sure you use a heavy inline fuse and at least a 30amp Relay for EACH fan, they do draw a lot of current.

If you wanna go electronic, HKS do a nice controller for dual fans so you can switch them on a different temps, it also controls IC water Spray, theres also a great one on Fleebay by Pivot.

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If you go with the above, or any Fan controller for that matter, make sure you use a heavy inline fuse and at least a 30amp Relay for EACH fan, they do draw a lot of current.

If you wanna go electronic, HKS do a nice controller for dual fans so you can switch them on a different temps, it also controls IC water Spray, theres also a great one on Fleebay by Pivot.

 

It's not cheap though, and takes up room in the dash somewhere. I made my own - small box from Maplin, 2 auto relays, a power distribution thingy for amps, thermostatic switch from X-eng (http://www.x-eng.co.uk/X-Therm.asp), couple of blue leds and a switch in the dash. Total cost about £50.

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If you go with the above, or any Fan controller for that matter, make sure you use a heavy inline fuse and at least a 30amp Relay for EACH fan, they do draw a lot of current.

 

Agreed. I blew a a couple of 30amp fuses in quick succession(they blew as the fan initiated).

I switched to a 40amp fuse and it's been fine since.

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I have the thermostatic switch from x-eng. How did you wire that all together Simon, could you do a diagram please?

 

Here you go, thought it was probably a good idea to do one so I know how the hell I wired it up if I ever need to fix it!

 

Basically there are two 30A auto relays that are wired direct to the +ve battery terminal (via a car stereo distribution block inside my box) - the output from these goes to the fans. The fan negatives are wired direct to the battery -ve. The input on the X-eng thermostat switch goes to a +12v ignition switched source - I used one of the VSV wires I no longer need. The two outputs (low and high) go to the relay coils, with the other side of those grounded. That gives you your basic operation.

 

I have a fan override switch with a LED backlight, and a couple of LEDs that show when the two fans are running. That's the bottom of the diagram. I needed to use a DPDT relay otherwise whenever one of the fans is on the light on the switch would light up. This is just a small current relay I had from Maplins. There are 5 wires that go from the control box to the dash (+12V permanent, two fan activity lines and two relay control lines). The ground I just connected up to a ground point behind the dash. You could get a permenant 12v from behind the dash somewhere too and save yourself a wire if you could be arsed.

 

Oh, I didn't show the fuse, which is between the battery +12V connection and the distribution block that goes to the relays.

FanControl.jpg

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It's directly connected whereas the electric ones have to turn the alternator to produce electricity (which loses some power) and then turn the motors to produce movement again (which loses some more).

 

I've seen this description a few times, true fans will draw more current, but unless you have a big i.c.e install then its readily available, as the revs increase the more the alternator can convert, there is no draw on the engine as the alternator pulley runs freely, so taking the 5kg viscous fan out is a plus.

 

Your only disadvantage is when your sitting at idle and you have the fans running, good for keeping temps down, but big draw on the alternator...which if its not up to the job will just draw straight from battery,

 

You don't want the fans on when you have enough air flowing through the rad anyway or they'll get in the way of that air, and it's a waste of power having them on when the temps are low.

 

Again another valid point, there is an optimum that the viscous fan can flow at above a certain speeds, so as Simon indicates it would be a waste to use them at high speed, pushing against flow. The electric fans are good, but they need to be properly ducted otherwise their no use, the standard ducting with the viscous fan is very good hence why theres not much advantage other than a little more control with the electric fans.

 

imho unless your a bling king, you would be better off staying stock...I can't be arsed going back now that I have already bought them:rolleyes:

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