Electric fan conversion - give me your thoughts

[Gary Allan]

I'm throwing an electric fan on the SE 2.5 4 banger. I'm torn on doing the home grown junkyard reclaim ..or buying the custom fit Flex-a-Lite shrouded Black Beauty (probably buy the recon/refurbished unit on ebay). The Flexalite has the advantage of all the mounting points for the ps reservoir and whatnot ..and conforming to the existing OEM available mounting points (no fab'ing at all).

Aside from the main fan choice, I've decided on a couple of other things.

I don't want the main fan cycling every time the AC compressor kicks on. I've decided to wire a separate 10" fan through a relay just for the AC condenser flow. The current mechanical fan doesn't do the job at idle ..so this make sense. I had considered not having any fan wired to the compressor clutch cycle. I reasoned that if I was running the AC ..and was not already providing enough foward movement to provide heat exchange for the AC, the engine temp would probably have the cooling fan running anyway.

..but not wanting to tear this all out again I figured, for the cost, I'd just wire its own fan. I can always pull the relay to test the theory later(I'm lazy - measure/think 25 times - assemble ONCE)

I going with either the older SPAL PWM controller or the newer V3 model. I don't see where the newer model would serve me better ..and the difference is about $40 (about $130 vs. $90 delivered).

The advantage of the Spal is that it you select two setpoints on the controller. When it hits the first setpoint, the fan operates at half speed (PWM- pulse width modulation). It then spans the two setpoints up to full speed. Appears to be a very smart box. It's also able to be mounted under the hood.

I had considered a Centech controller.

It has the economy of a knob that you dial into your gauge reading (temp sensor output). It has no variable speed option and needs to be in the driver compartment. That means (at least without more relays/wiring) I need to run higher current wires through the dash.

Both have AC relay features, but I think the direct connection to the smaller fan will, on average, draw less current, minimizing the alternator drag.

Both are capable of just tapping into the OEM temp sensor.

This is going to be in concert with an inlet side thermostat installation. A fellow member turned me on to a home fab'd remote thermostat housing. I just need to reroute the bypass return (heater circuit) to the unit and reverse bias the thermostat to sense that temp.


Any objections ..cautions ..just plain old "if man were meant to fly, he'd have wings comments?

 

[AcuraTech]

Nice project! Judging by all that you just said it sounds like you're more than capable of understanding how to do it properly.

Do it up and then post the results!

 

[eljefino]

As an engineering footnote one of the dual fans in my olds silhouette van is whisper quiet at full +12V, as is the dinky fan in my sister's hyundai accent. Both are likely small enough they could sit next to bigger, full power fans.

Could make such a dinky fan run with AC; you'd never know it.

Personally I like monitoring the radiator temperature for these projects: Engine will sit at thermostat temp for some time while the radiator gets warmer and warmer until they both start getting above thermostat temp. If you can catch this upswing and start cooling the rad, on a low fan setting, at, say, 170'F, the engine won't see any thermal stress at all!

You could set up a logic sequence with more relays where if your foot is on the brake and the AC kicks on, so will the fan. You'd likely be stopped in traffic then. Keep the relays under the hood b/c they'll drive you crazy clicking whenever you hit the pedal!

If you have spouses etc that have to ride in the jeep, they won't appreciate the MPG improvement you get... but may wonder if the AC doesn't work as well as it used to.

With that PWM doohickey you could wire up a voltmeter with a custom meter background from your laser printer... "Low" then graduations up to "100% fan".

 

[StevieC]

Originally Posted By: eljefino
... You could set up a logic sequence with more relays where if your foot is on the brake and the AC kicks on, so will the fan. You'd likely be stopped in traffic then. Keep the relays under the hood b/c they'll drive you crazy clicking whenever you hit the pedal! ...


Nice!

 

[Gary Allan]

Quote:
You could set up a logic sequence with more relays where if your foot is on the brake and the AC kicks on, so will the fan. You'd likely be stopped in traffic then. Keep the relays under the hood b/c they'll drive you crazy clicking whenever you hit the pedal!

Excellent. Maybe later when I need to add more complexity (need to improve the wheel).

I was actually looking for some integrator that would read VSS output and have a relay cutout the AC fan input above (something like) 25 mph. Then I could use the main fan with the AC.

I'm sure that it can be done, but that's too much searching and "getting there from here" type thing.

Quote:
As an engineering footnote one of the dual fans in my olds silhouette van is whisper quiet at full +12V, as is the dinky fan in my sister's hyundai accent. Both are likely small enough they could sit next to bigger, full power fans.


The rad configuration doesn't lend itself to dual fans. My minivan basically had a side by side rad/condenser.

I have noted that many contemporary vehicles are almost silent at idle ..at least in comparison to my jeep. Loads of noise producing things.

Quote:
Could make such a dinky fan run with AC; you'd never know it.


I had thought of the junkyard route to find such a fan. I just don't want to play parts scrounger right now. Normally, I'm all for it. I don't know how loud the 10" fan will be.

So ..10" pusher in front for the AC ..16" puller for the main cooling :shug: It should be quieter just without the whirring fan clutch spinning all the time.

 

[Gary Allan]

Opps edit time:

Quote:
Personally I like monitoring the radiator temperature for these projects: Engine will sit at thermostat temp for some time while the radiator gets warmer and warmer until they both start getting above thermostat temp. If you can catch this upswing and start cooling the rad, on a low fan setting, at, say, 170'F, the engine won't see any thermal stress at all!


I imagine that would work. I don't know how well it accounts for varied pump rates. I think regulating the inlet temp to the engine will dampen any temp swings. I'm starting out with a 180F inlet thermostat, while leaving the 195F outlet 'stat intact. A 160F will be installed if 180F proves to be too high. I could get into a situation where cooling to 195F outlet may not be possible with 180F inlet coolant. That would allow the fan to run as fast as it pleased with no off time since it could never reach the setpoint.

There's probably some minor tweaking to do to make everything modulate smoothly.

 

[OVERKILL]

Gary:

Take a look at the DCC controller, they are quite popular in the Mustang community. On the other hand the "Black Tragic" fans have a bad name as not being able to keep up to the vehicles cooling requirements.

I've done the electric fan conversion on both the Mustang/Capri and the Lincoln, using relays to handle the load of the fans (SHO fan and Mark VIII fan), since they draw substantial current on start.

 

[mechtech2]

I think it is wise to use all the fans on high when the AC is on.

 

[Tosh]

"Don't fix what ain't broke."

 

[Gary Allan]

"Black Tragic"

Good one!

I'm well aware of the Taurus MEGA whirlwind fan conversion. Another one of Ford's better ideas (really).

Keep in mind I'm only cooling 2.5 NA liters with the same rad that adequately cools a 4.0. I have a mind boggling 150hp+/- (yeah, man, but it's old fashion hp. Not that new junk

)

Thanks for the tip on DCC. I never heard of Delta before and I'm still reading.


mechtech2: Even @ 70mph with a radiator that's 90° to the wind with about 4^2' of uncongested air flow? My air works fine once I'm off idle in traffic. I could see it if I had to "induce" flow over the condenser in some aerodynamic setup ...but we'll see what happens.


Thank you Tosh. I was hoping, and indeed asked for, at least one "if man were meant to fly, he'd have wing" post. Normally I tend to agree with most mods to stock. This is a fairly (in my mind) modular alteration. Everything is bolt on and all the R&D is mostly long done by someone else.

Mechanical fans are pretty antiquated and electrics are well proven for decades in the field. HP cost about $75/hp in these engines and this is also true in this installation. If I manage 3 or 4, it will be about right.

 

[brianl703]

Originally Posted By: Gary Allan

I was actually looking for some integrator that would read VSS output and have a relay cutout the AC fan input above (something like) 25 mph.


Frequency to voltage converter and a comparator would be one way to do that.

 

[brianl703]

I think the LM2917 can do all you need.

 

[Gary Allan]

Yes, it does. Now to buy just one and package it for plug and play ease of installation (add one year

)

 

[IndyIan]

Well its sounds like you know what you're doing. Just to be clear, are you replacing a mechanical fan? A guy on my tracker/vitara forum replaced the fluid coupling fan with an electrical one and got something like 1-2 mpg better mileage, so a 5-8% improvement on a 20-25mpg truck. Not bad at all.

 

[Gary Allan]

Yes, the mechanical is coming out. If an electric clutch was easily workable, I'd surely consider it. It worked well on my Peugeot 504 diesel wagon. I've seen these for bigger installations, but didn't see a practical way to integrate it to my engine.

 

[brianl703]

Originally Posted By: Gary Allan
Yes, it does. Now to buy just one and package it for plug and play ease of installation (add one year

)


Digi-Key stocks them and will be happy to sell you just one, plus $2.50 shipping.

 

[meep]

I would run at least one fan during AC on. Otherwise the high side pressures will be a bit high-er... more strain on condenser (right? I get them confused) and compressor.

M

 

[JHZR2]

You could readily pull the aux fan setup froma w123 MB diesel. it is set up to turn on the aux fan at a certain water setpoint and AC refrigerant pressure... Two taps to turn on, all mechanical, and an existing system - you would, of course have to play the NPT game to tap into the right systems... but the system is tried and true for an aux fan.

 

[mechtech2]

Right. At highway speeds, the fan is not needed like at slow speeds.
But at slow speeds or stopped, you need all the fans/cooling you can get for your AC condenser!

 

[kaboom10]

Just did mine using a dual fan setup off another Ford vehicle. Ran 2 Derale electronic adjustable controllers. One is set to go one early and the other comes on a bit later if needed. Temps haven't got up to their hottest yet but I'm running the same water temps I was when the thermostatic fan was on. Engine revs a lot faster now.