Building A Custom Fan Shroud - Steel Vs Aluminum

Cant find a pre-made shroud I like for my radiator. Figure I'd like to build my own. I know aluminum is the standard, it is lightweight and looks pretty. But steel is cheaper, easier for me to weld and my engine bay isnt that pretty anyway. I only have my Miller 211 wire-feed. It has a spool gun, and I have argon, but I think thinner aluminum sheet would be difficult.

Weight isn't a huge concern to me, I plan on designing it so that the majority of the weight would be supported by the cross-member. It also needs to support the weight of the electric fan. I was thinking a 14-16ga steel.

My other option is to just get some 1/4" aluminum plate and build something close to this:

Cant find any scrap, and the metal yard will only sell a 4'x5' sheet for $186

Steel would allow me to build a legit shroud, whereas the aluminum plate allows me to build a solid mounting plate for the fan, relying on the 2750 CFM rating to keep things cool at lower speeds.


Any thoughts are welcome....

 

How about fiberglass? Google it. Have seen a few made that look factory. The concept is similar to making custom stereo speaker enclosures.

 

Not sure of the type of radiator your running. But those type of fans can be attached through the radiator with ties that usually come with it. Usually a shroud isn't nessisary and might even block airflow. I know a lot of guys hate electric fans and even I tend to have a love hate relationship with them. But I've had real good luck whenever I used them. In the jeep, space is a premium and the electric fan is king. I usually mount them as pullers, but on my 3A I did the pusher. Not as efficient but, after I got the thermostat issue fixed it seems ok. On the 3A I used a tempature controlled switch that screws into water jacket from summit. On at 180 degrees and off at 170 degrees. It uses a relay to trigger and hooks direct to battery power with a fuse. Back in the day, I used a toggle switch and would monitor temp when stopped, or slow. Turning it on and off manually. Thats a lot of work. Technology wins. If you need a schematic, let me know and I'll find one, or draw one up and post it.

Cole

 

did this myself. jp mag has an article on how to do it, was easy works mint.

 

Steel sheet is everywhere as a scrap, cheap and easy to work with. Get some 14 gauge or 12 gauge and have at it. Make it so that it allow 1/4~3/8 " off the fins to allow the fan to pull air across all the fins. Just copy the ones you see in summit or jets or speedway for your particular use. The fiberglas idea seems like a good deal too.

 

Most electric fans already have a shroud covering the blade........does yours? ............can't see why adding another would benefit unless your blade is exposed? Getting the proper sized electric fan & shroud that fits the radiator core is what I would do.

 

Yes, plus this fan is HEAVY at just under 5lbs.

It has a shroud covering the blade. My radiator is a Griffin 2 core aluminum crossflow. The radiator core surface is 17" wide x 14" high. A 14 inch fan leaves 1.5" on the sides of the core, so the fan will not pull any air through the portion of the core not covered by the fan - not an issue at highway speed, but this rig will see 65-75% trail use, and low speed cooling is the priority, especially in Southern California.

Had to mount as a puller - only 1/2" clearance between the front of my radiator and the back of the grill.

Thanks for the schematic offer, but I got that part figured out. I used a Summit switch as well and went with on at 185/off 170. Wired in a relay with the switch on the ground lead. I also installed a switch in the dash that will cut the positive power to the relay in the event I want to force the fan off in the event of a water crossing. The switch is protected by one of the flip covers, and when activated, turns on a 1/2" red LED warning light on the dash.

Fiber sounds cool, but I dont know how it will support weight, and I've never worked with it before. If I can weld / bend up something out of 12 or 14 ga, I'd rather give it a shot. Worst case I'm only out a few bucks as opposed to the cost of the aluminum. My local yard has a scrap bin, but they are 40 minutes away and cant give any info over the phone as to what they have in surplus. Guess I'll make a trip down there and see what I can come up with.

 

If it's a cross flow, as long as the top-to-bottom area is covered, you're good. The water in the 1 1/2" on the sides are crossing in front of the fan while cycling. I think in your case, a shroud may not do much, if anything.

I say, try it without a shroud. If you have cooling issues, you know what to try next.

 

You said this a MPFI engine. I don't remember which ECM you said you are going to use other than one from a similar vehicle that the engine came from. With that said, the ECM will probably expect to see the engine operate with a 195* F thermostat. That means the fan should come on at 210* F and off at approximately 197* F, slightly higher that the thermostat temperature to prevent short cycling the fan. The OEM fan set point is probably higher but can easily be reset. The ECM should be fully capable of controlling the fan without the need of a Summit controller. Check your ECM wiring diagram for the correct pin to wire to fan relay.

 

If you have anybody in the HVAC world you might want to press them for a favor. I think that if you are going to use steel that 16-18 gauge material would be plenty stout with or with out welded corners. in alum .090-.125 works nice. I have used both and also used a steel door jam for a brake. I'm fortunate to have a press brake at work that can be used for home projects now. If you have the means and if it would fit I would suggest going alum and a large mechanical fan. I have a 7 blade clutch fan off a wag in my 5 and it works great. But I understand using what you have and your location(the heat).

My setup, not the greatest pic but you get the idea. It moves a lot of air, holds a 5"x7" piece of paper on the grill at idle.

 

The ECM is GM service number 16244210. It is the recommended one for use with the Painless Performance stand alone wiring harness I am using. I confirmed with them this morning that their harness does not have a provision to control the fan through the ECM. They stated this was due to the fact the majority of engines the ECM was used for had mechanical fans.

I will check into the temperature range though and get a different switch (its just the cheap, 1 wire ground type that screws into the block) as needed - I didn't even think about that. Thanks for the heads up!

 

Sure would make things easier, but there isn't a lot of room under the hood of an MB. As I sit now, the radiator is only 1/2" behind the grill and I have just under 3.5" between the front of the water pump and the core. The radiator sits high enough that a 14" electric fan (centered on the radiator) allows for a fan thickness of about 5.5"

That makes sense. I have a big sheet of 14ga steel in the scrap pile. I might try to fab something out of that to mount the fan. I guess the real delima is/was how to mount the fan without using the zip-tie method, and a full shroud seemed like the best solution. Something kind of like this:



At least the weather is nice and I've got nothing else to do today...

 

A counter-productive side effect you might run into with a shroud is that you are taking 238 square inches of radiator surface area and squeezing it through 154 square inches of shroud opening, minus the fan parts that are in the way. It's great at a standstill, forcing air through every inch of radiator, but at speed, it's slowing air down.

Just something to consider.

 

I actually needed less air to flow when driving over 15 MPH. No longer does my temp go down to 165 driving at 25+mph because of it. It stays at 180. Aside from the extra current requirements the electric fan has been great for me so far. The higher coolant temp makes my engine run much better.

The pictured shroud above is exactly what I am talking about.

 

Thank you everyone for all the input. I ended up building a shroud. Rather than take up bandwith here, I just updated my build thread. Vortec V6 in a flatfender with a power Saginaw conversion.

 

From what I understand, the higher coolant temps are needed in a stock vehicle for emission control. They heat the catalytic converters to help burn cleaner. there is no need to run motor with greater than a 180 degree thermostat in your application. The painless harness will clean things up nicely. The temp switch you have is perfect to run the fan and will work great. The computer might want to tell the stock fans to turn on at 205 degrees, but there will be no connection, so it won't trigger anything. I've used the computer to turn on fans before with good success. When computer senses preset motor temps it sends a ground signal to close fan relays. It also senses vehicle speed and turns off fans when your on the go and back on when you get slow. That requires a speed senser, which even complicates things more. Simple is best way to go.