mcrisfield Posted October 2, 2009 Report Share Posted October 2, 2009 I recently purchased a new custom radiator that just barely fits and I had to "customize" the fans to fit and they just barely clear the belts now. I need a fan that is under 3" so I'm looking at maybe two cheap 12" fans at 2.5" depth, wired to run at the same time or maybe a 12" Zirgo (1250cfm) and a 10" Zirgo (1500cfm fan). What I would really like to know is what the stock fans CFM numbers are. Anyone know? Here are the two cheap 1600cfm 12" fans (but I'm not sure about their noise/reliability): My link Any advice is appreciated. Thanks, Mike Link to comment Share on other sites More sharing options...
psu_Crash Posted October 2, 2009 Report Share Posted October 2, 2009 I think the stock fans are about 3000cfm combined. Jolyrjr said a while back that 2000-3000cfm should foot the bill but I would want to be on the high end of that. Your 2750 combined should be ok as long as you don't do a lot of stopping in traffic on hot days. Link to comment Share on other sites More sharing options...
ucw458 Posted October 2, 2009 Report Share Posted October 2, 2009 Actually I flow tested a set of stock fans. I took videos of it but never edited them. It's more like 3000-4000 cfm. I didn't make covers for the fans to seal them against the meter. I just held them up to the meter and measured the flow. There was alot of air spilling out of the meter not being measured so my cfm #s were on the low side. I came up with about 3200 cfm that way. When I get around to it I'll make some covers for the fans and test them again. Link to comment Share on other sites More sharing options...
mcrisfield Posted October 2, 2009 Author Report Share Posted October 2, 2009 Thanks for the info guys. I ended up ordering the two 12" fans flowing 1600cfm each. I will run both at the same time so I should get 3200cfm (around stock). They were only $77.97 shipped so I can't beat the price and I think they should fit perfectly but I'll update the post when I have them installed and have a chance to test them. Mike Link to comment Share on other sites More sharing options...
Indiana Posted October 2, 2009 Report Share Posted October 2, 2009 Your stock primary fan has a full shroud around it to force that entire half of the core to have air flow through it. If you do not duplicate that shroud or mount the new fans in the old shroud you will have over heating problems. The stock specs were never given for the fan motors, only their rpms. The core size of the radiator slightly increased as the intercooled models were introduced and that was when they added the electric fans. There isn't a shroud on the secondary fan of 5sp cars and that motor and fan are smaller. Automatic transmission cars have a full shroud on the secondary fan and use the larger motor and fan as the primary. Without a shroud the only part of the core that will have air pulled through it is where the blade rotates and then it needs a ring around the outer diameter it can't just be a blade spinning in the air. Good time to test your fan sensors. What condition is your secondary fan motor in? Link to comment Share on other sites More sharing options...
mcrisfield Posted October 2, 2009 Author Report Share Posted October 2, 2009 Thanks for the input. I think I'm going to fab up an aluminum shroud to enclose both of the new 12 inch fans so hopefully with both those fans in one shroud activating of the primary sensor that should do the trick. Mike Link to comment Share on other sites More sharing options...
Indiana Posted October 3, 2009 Report Share Posted October 3, 2009 Remember the shroud acts like a funnel, its not just to block off part of the core it has to redirect the flow into the fan blade. Link to comment Share on other sites More sharing options...
jolyrgr Posted October 3, 2009 Report Share Posted October 3, 2009 (edited) I think the stock fans are about 3000cfm combined. Jolyrjr said a while back that 2000-3000cfm should foot the bill but I would want to be on the high end of that. Your 2750 combined should be ok as long as you don't do a lot of stopping in traffic on hot days. The 2000-3000 I stated before was in reference to an aluminum radiator set-up. The heat transfer of the stock copper/brass radiator is not going to be as efficient (especially when given the age of most stock units), so I would definitely aim for the 3000cfm range. As Indiana stated, a proper shroud is going to direct the airflow thru more of the radiator, increasing the efficient transfer of heat. You also need to realize that the push-thru style of mount is not the best for the radiator, as they will rub on the rows/fins and can create a hole. They are also prone to "back-out" causing the fan itself to possibly damage the radiator. JR Edited October 3, 2009 by jolyrgr Link to comment Share on other sites More sharing options...
ucw458 Posted October 3, 2009 Report Share Posted October 3, 2009 You also need to realize that the push-thru style of mount is not the best for the radiator, as they will rub on the rows/fins and can create a hole. They are also prone to "back-out" causing the fan itself to possibly damage the radiator. JR That's more of a problem with crossflow radiators, not as much with downflow. But yes I learned that lesson the hard way. The fan bounces up and down until it damages the radiator. I had one on my old dodge for a month before it wore a hole in the radiator core. The best way I found to run one of those is to line the outer edge of the fan with foam tape. The foam tape should be inbetween the fan and the radiator. That adds a cushion and stops the fan from bouncing around and damaging the radiator. Remember to put foam on the push through mount too so the plastic end doesn't press against the radiator core. Then make the pull through mounts as tight as you can. I've never had one come loose when I did it that way. But, a fan shroud mount is a much better way of doing it. Link to comment Share on other sites More sharing options...
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