348 Radiator Shroud Project

Simple project time. The 348 Driver radiator has roughly 1/3 of the fan not under fan vacuum. See the picture below. The 348 generally does not have cooling issues but when I get stuck in traffic dead stopped bumper to bumper in summer I start to worry. Seems a shroud that would apply vacuum to the entire fin surface area is both easy to do and would make a good modification that is as easy to reverse as it is to unbolt it. To allow flow when under way, air escape flaps wold open to let air escape the shroud but under idle speed they would suck shut and the suction would cover entire the finned area.

The 355 fan takes almost twice the constant amperage, so the 348s 1650 cfm fan is ideal adding a larger fan and increasing amperage is not ideal for me. The 348 fan (now a new SPAL fan) works but its overall efficiency could be improved. I would bet with a shroud the temps would drop very quickly and have a much easier time maintaining max fan switch temp limit even in adverse conditions. Plus it would provide a much better place to mount the PWM controller.

I will fabricate 3. It will be done in CAD and water jet cut and bent with a brake and use premium German flap material. One shroud for me and 2 for some tbd folks out here if anyone has internist at a reasonable cost, free.


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Initial design, dimentions are not nailed down but will clear the inner fender flap.

Ordered flaps that fit my size needs from older German car model.

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I responded to frankly... good questions. Dialog is great great to share thoughts and knowledge and a chance for me to pick up some new knowledge. Worst case I take it off and it was great fun! But I think it will work there is a HUGE market for custom rad shops and mfg's like Spal and Derale making these for high performance cars let alone fan shroud kits from Jegs and Summit etc making these flap based electric fan shrouds. Some of my answers may be inaccurate they are observational based on what other cars do to optimize the fans. btw the hole you see is the ID of the fan the OD is 1 inch bigger and the fan goes out to the side edges of the shroud.

I think your right on in that we will wait and see. My wager is when the fans kick on the temps drop so fast you see the needs move and it will fail to get hot in traffic and on the highway it will have o effect. Or this is what I hope.

1) Isn't the exsisting fan shroud (outer black ring) positioned close to the radiator? Thus, a minimal gap would exsist for drawing more air through the upper part of the radiator when the shroud is in place. - The current fan actually sits ON the radiator itself. It is pressed onto it rather hard actually when you tighten down the wings. There is an o-ring that does not come with new fans you have to remember to switch over btw. The shroud would now lift the fan .5 inch from the radiator.

2) As is, the fan creates a low pressure ares on the front side of the radiator it has been denonstrated that, as a result, air is drawn through the area not covered by the fan from the back side when these cars are standing still. The shrould and flaps would stop this and result in drawing air through that area from the front. Better or worse???? - The current fan ultimately pulls air through the section covered by the fan, the areas not covered by the fan has no vacuum draw. The shroud by listing the fan does the same thing as before except applies a vacuum to the entire finned area. Same low pressure on the front but it gets air pulled across ALL the fins sucking from the back and it escapes through the fan exhaust. BTW The 355 has a much bigger fan it covers almost the whole area except corners of course. On mine I waited for the fans to come on with the wheel and liners off and the air flow is mad from the back of the fan but up top where there is no fan you don't really feel flow per say mostly turbulence as evidences by a small sheet of paper flapping every which way. Most certainly not flow like the back of the fan in any event.

3) When moving, although the flaps will open, they will still provide some restriction to air flow. Additionally, the corner areas around the fan will now be covered. Net, probably lower air flow when moving and fans are off. - I'll add smaller flaps in the bottom corners, Spal sells the flaps actually. But conceptually a gas like water takes the path of least resistance and will flow out as long as there is a reasonable path where hot air escapes at a rate faster then it sits static and heats up. This is commonly done on hot rods and OEM cars with no problems. My Sirocco used to have the flap set up actually. Spal fan shrouds come this way, this is used on Golf's Jags, Volvos and many other cars, I did not invent it I am just doing what has worked for decades.

4) Lastly, the fan can only draw so much air through the radiator. The shrould will not increase this air flow, only alter where the air flow is. Whether the air flow is more of less will be a function of whether the resistance to air flow is increased or reduced. Additionally, cooling effect will depend on not only amount of air flow but also flow velocity. - Yes the shroud will not increase total flow (1640 cfm) what it will do is spread out the existing cfm across a larger area instead of a 11.25 inch circle. Right now it draws lots of air through a small area.


Below is for example:

• OEM Ford Mondeo with flaps and a PWM controller
• A Universal SPAL replacement unit
• Street trod as example.

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Yes I believe we are right John. Would be neat for a 355 to test it too, pretty sure radiator dimentions are the same

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Updated design, move radiator to the center and create straps to hold the flaps. The bottom one has straps that curve around the OD of the fan and mount to the top of the flap. The top one mounts to the top of the flap.

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Ohh ya I know Ron, if and when mine go I will send it to him to duplicate in aluminum.

 

Updated Radiator OD dimensions if anyone ever needs them. They are close and I am sure a 355 radiator will dimentionally fit in a 348. Can't say about fittings though.

348 = 16 7/8 L x 13 7/8
355 = 17 5/16 L x 14 9/16

Here is is final size made out of 3/32 5052 Aluminum. Ordered 3 from machine shop will be here in about a week. Not much restriction is here.

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First attempt is in, it is think, its not floppy sheet metal it is stuff, it is in flexible you can see it next to a credit card but it is very light. The top and bottom side have a 1/6 relief you can see sort of in picture 3 so I can add rubber channel to protect and seal against the fins. Will need to see if I weld the corners or what not.

Anyone in central NJ have a tig welder in central NJ any one have one?

I have 3 of these units.

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i replaced my fan swirch with a 355 switch. This particular one according to my heat gun on the thermostat housing kicks on at 197 and off at 191. My 348 switch went on at 190 and off at 184. way too cool and fans fo on before thermostat opens. The new switch is great temp wise and keeps engine efficient burns off water etc etc. I want to keep it in range as tightly as possible and quickly as possible. The pwm makes the amp spike all but non existent so i dont need to worry about the fuse board frying something due to heat on repeated fan on and offs with the amp spike. Seems more a 355 concern with +10amp over oem fuses being used (according to my reading out here) but still I worry.

Ill be working on flaps this weekend as well as install. I expect the fan to run veryl short periods and I expext to see the temp gauge visibly drop rather quickly. even now when i get back from a drive and car is hot and I pull in garage the fan can run for several minutes at a time after parking.

the goal is a better system than stock operating at better and narrower range deapite adverse conditions. hope to never see > 200 degrees.

hell, maybe it wont do diddly. Guess well see!

 

jamminv to 80s music, test fit and clearanced, optimistic so far.
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Found something I did not like in the design, so I did SLIGHT redesign and ordered 2 new ones. Did not need to but I tend to obsess on details. Will be here EOW. Once all drilled and ready I'll powder coat it silver then install. So I will have 1 extra. Back in a week.

 

Updated design with fan fitted. You can see the new teeth to prevent the flaps from getting sucked in. And ther is it test fitted, it is snug. Need to work out the 4 mount holes, then put the PWW back in, re-splice power wires with sleeveless stainless splices using hydraulic crimp, cover wires with thermal insulated covering it with, plug it is and test.

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New design is in after some travel and work finally got it done. the PWM with the shroud interfered with the fender liner so I relocated it. The fan is also centered now. The plugs are far from the exhaust now. I added a U-channel seal at the top and bottom where there is no flange as seen in black in the top picture. The flange has a thin RTV seal. I also made the bottom flaps extra long for weight so they suck down better.

The results are as follows, in the garage idling using a 355 temp switch which keeps the car slightly warmer than the 348 switch where the fan switched off at 185, now it switches on at 197 and off at 191. The fan from the side stakes really howls as it sucks air in now. The fan comes on for a very short period then goes off, then back on and back off instead of on staying on for 2 min when idling. Its winter here so we'll see in the summer but last year in the winter the fan did not do this it came on up to 2 minutes when the car sat idling for long periods.

You can see and hear the fan come on and the PWM ramping it up softly over 3 seconds then lets it go full tilt instead of the instant 30 amp draw on.

You can see the difference in fan coverage before and after a shroud. Without the shroud 1/3 of the radiator has no fan support on my original testing of the PWM before the shroud in the last picture.

 

Took it out let engine get up to temp as well as gear box oil. Put AC on (brrr) and sat in parking lot after start and stop drive in traffic. With engine heat soaked the fan comes on and 32 seconds later the needle visible starts moving down and 23 seconds later the fan cuts off. So under a minute. This happend 5 consecutive times before I got bored and continued to drive and when I backed into the garage did it again and got the same result. I did it with the dash lights on you can see the lights dim slightly when the fans come on but the lights do not dim as much as they used to. You actually hear the passenger fan before the drivers fan comes on full tilt about 3 seconds later then you really hear it in the car now. I think I'll put a PWM controller on the smaller passenger radiator.

Crappy picture basic LG phone....

 

For completeness, I did put a PWM on the smaller fan and the power dip when they went on is completely gone as mentioned on post 19. No noticeable dash light dimming now.

 

With the engine currently out figures a good time to post a better view un-obstructed, you can see the pwm mounting location as well.

I bet this type of thing would benefit the 308/328 line up.

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Nah I just designed in to CAD and had a local machine shop make the parts. Then I used vw radiator flaps and cut them. Then bolted the retaining strips (also cad) to the shroud frame. Mirojub helped with the wiring and outside that, it just plugged in and bolted up to existing radiator fan mount holes. Easy peasy. I made like 6, offered them up, had no takers so I chucked the spares.

Tell you what, at idle if really focuss the full fan draw through the radiator. You can head the difference. Pulls the temp down quick.

I head it going off frequently and and really glad I have the pwm, the poor plastic fuse panel.

In post 18 above you can hear it soft starting in the vid.

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