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Old 06-13-2020, 10:55 AM   #21 (permalink)
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Originally Posted by EcoCivic View Post
Thatís the whole point of adding flaps. At speeds where the fans arenít needed anymore, say 40+ MPH, the fans and shroud could block the natural airflow through the radiator. The point of flaps with holes behind them is to allow natural airflow through the shroud when driving at higher speeds when the fans arenít needed. The flaps get sucked closed when the fans are running when stopped or at low speeds and they get pushed open from pressure in the shroud when driving at higher speeds. I just donít know if it would help much since there isnít a lot of my radiator that is covered by the shroud, most of it is covered by the fans.
Forced air will pass right through the fans and even turn them. If you had a way to measure, you would maybe see a little power generation. You're fine. I vote no flaps.

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Old 06-14-2020, 01:27 AM   #22 (permalink)
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Considering what happens to some longitudinally-engined Volkswagens which have their radiator behind the left headlight, which tend to overheat more often when the radiator flaps are removed, seems like your idea of resorting to flaps at speeds which allow a natural air flow is worth.
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Old 06-16-2020, 01:36 AM   #23 (permalink)
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Originally Posted by cRiPpLe_rOoStEr View Post
Considering what happens to some longitudinally-engined Volkswagens which have their radiator behind the left headlight, which tend to overheat more often when the radiator flaps are removed, seems like your idea of resorting to flaps at speeds which allow a natural air flow is worth.
Thanks, I guess I will pull the radiator back out and install flaps then. I don't see how it could hurt and it may help a little so why not. I also came up with the idea of adding flaps on the top and sides of the shroud to allow airflow through there at speed too, I could drill holes and cover them with rubber flaps. I wouldn't install flaps on the bottom of the shroud though since they would hang down and not get sucked closed when the fans are on.
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Old 06-16-2020, 08:57 PM   #24 (permalink)
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Originally Posted by California98Civic View Post
Forced air will pass right through the fans and even turn them. If you had a way to measure, you would maybe see a little power generation. You're fine. I vote no flaps.
I never thought about power generation. I may wire a multimeter to one of the fans and see how much voltage I can get out of it while driving down the highway. Totally useless information, but still cool to know (in my opinion anyways)
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Old 06-17-2020, 07:14 PM   #25 (permalink)
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Not so sure if it would be so easy to find a motor-generator compact enough to drive a fan when required and to harvest energy while cruising with the fans off.
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Old 06-17-2020, 07:30 PM   #26 (permalink)
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Not so sure if it would be so easy to find a motor-generator compact enough to drive a fan when required and to harvest energy while cruising with the fans off.
The fan motor already acts like a generator when spun. The problem is that adding a load to the motor would make it significantly harder to turn and would therefore create more aerodynamic drag as the air flows through the fans and would restrict airflow more, so the power wouldn't be free. Whether generating power with the fan motors would be more efficient than generating that power with the alternator I have no idea.
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Old 06-18-2020, 12:03 AM   #27 (permalink)
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I have an update. I pulled the radiator back out and added flaps to the shroud just to be safe. I can not have this car overheating under any conditions, it is my only functional vehicle at the moment and it must be reliable.

I finished installing my new AC condenser and did some testing on my new fan setup to see how well it works and it is definitely a massive success. I ran the car for about 30 minutes bleeding the air out of the cooling system, recharging the AC, and doing testing and the highest coolant temp achieved was 186 degrees after 30+ minutes of idling with the AC on in a 100+ degree garage. 186 degrees is totally normal, the coolant runs between 182 and 188 when driving normally so 186 is great. The lower radiator hose wasn't very hot either, I could comfortably hold it. This tells me that the cooling system still had a good amount of capacity left even under those conditions. I plan to do a more scientific hot idle test on a hotter day, measuring ambient temp in the garage and such.

Also, while I had my AC gauges on it, I checked pressures with the gaps on the sides of the radiator open and closed and I found that the high side pressure seemed to be about 10 PSI lower with the gaps closed since less hot air from the engine compartment was getting back in front of the condenser through those gaps. I think that's a decent drop for such a simple mod and I suspect the difference may have been much greater with the hood closed and the bumper on since the engine compartment would have been under more pressure and the bumper may be under slight negative pressure, increasing the amount of hot air that gets pulled back through those gaps and ends up in front of the radiators. I didn't think to close the hood when I tested the pressures, but I will try that when I test this again.
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Old 06-18-2020, 08:01 AM   #28 (permalink)
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Any pictures of the actual flaps you made? How big were your cutouts? How much overlap around the edges with the rubber?
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Old 06-18-2020, 05:49 PM   #29 (permalink)
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Any pictures of the actual flaps you made? How big were your cutouts? How much overlap around the edges with the rubber?
Unfortunately I didn't think to take pictures while the radiator was out of the car, it was almost 4 AM by the time I was done. Basically what I did on the top and sides of the shroud is I drilled large holes and covered them with rubber flaps I cut out of an old bike inner tube and secured them with self tapping screws. I did this along the entire top of the shroud as well as on the sides. I wasn't able to do much on the front because there simply isn't a lot of shroud covering the radiator and the corners were too small to add flaps to. Also, as you can probably see, there is a bar that goes between the fans, so putting flaps behind that bar would have been pointless. But what I did is I used a thin sheet of flexible clear plastic to cover the holes and secured it with self tapping screws. I did this on the top part of the shroud between the 2 fans, but I couldn't on the bottom because of the support bar. I didn't cut too much out because I didn't want to weaken the shroud or suck the flaps in.
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Old 06-18-2020, 09:58 PM   #30 (permalink)
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Originally Posted by EcoCivic View Post
Whether generating power with the fan motors would be more efficient than generating that power with the alternator I have no idea.
It doesn't seem to be more efficient.

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