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Can you increase A/C Blower Output & where to buy knee pad vents?
I have a few questions for you A/C gurus out there:
1. Is there anyway to increase the actual air flow from the A/C blower into the cabin? Not with just a bulkhead vent, I am talking about with a bigger fan or motor. 2. Where can you buy new A/C vents that are incorporated into the knee pads? I used to own a SC and it had really nice ones installed not the early real big versions that I have seen. 3. Has anyone ever removed the rear condensor all together and just gone with one condensor either in the front or one in the wheel well? It seems to me that the back condensor absorbs more heat then in disapates. I even have fans on mine in the deck lid.
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Rodney Nelson - '72 911T (Undergoing Full Resto), '82 SC (Grand Prix White) Gone for 20 yrs and now back, '86 951 (Guards Red) Caught Fire, '71 911T (Tangerine) Sold, '72 911E (Grand Prix White) Sold, '86 951 (Black) Sold, '79 SC (Grand Prix White) Sold, '71 911T (Irish Green) Sold |
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Join Date: Sep 2001
Location: Kerrville, Texas
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If there is a way to increase the output then I'm in. I'm getting an R12 charge next week (its been over a year) and will ask the shop owner. He's been in business since 1973 so should know something about ac systems.
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1987 911 Guards Red Targa, nearing 200,000 miles, lowered, 7's & 8's, 964 grind cams from John Dougherty, A.P.E. Mass Flow Sensor with chip to match, cat bypass, strut brace, dual out muffler. Will consider newer model in 8 years when I turn 75 and then maybe not. 2012 BMW 528i (wife's) 2007 Toyota FJ (rain and off road days) |
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increasing cfm
We tried using a fast motor in the Behr box, though it can be done there are mod's you need to do and it brings you close to potential evporator core damage if you don't do it correctly.
However the the gain is not that significant vs. the cost and time with respect to swapping motors. You could approach the increase in rpm's another way, either increase voltage, which means things will not last as long as you would wish them to last; or re-wind the motor. On the second idea you need to find old farts who still remember how to remind the arms from the slot car era. Unfortunately the Behr knee pad unit does not leave you much room to increase the vent size, you will see when you start taking it apart. There is someone on the west coast I recall that may have replacement vents; you'll have to describe the design of your knee pad when you chat with them. You could drill through the underside of the knee pad's plenum or plastic perse and simply hang a few 90 degree outlets that swivel! |
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I was looking for the entire knee pad assembly with the vents. They used to sell them new somewhere?
Also, I am not sure how the fan assembly works, but you would think maybe with some slight mods you could just insert a new assembly with more CFM output.
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Rodney Nelson - '72 911T (Undergoing Full Resto), '82 SC (Grand Prix White) Gone for 20 yrs and now back, '86 951 (Guards Red) Caught Fire, '71 911T (Tangerine) Sold, '72 911E (Grand Prix White) Sold, '86 951 (Black) Sold, '79 SC (Grand Prix White) Sold, '71 911T (Irish Green) Sold |
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I installed another fan motor for my evaporator and get really good air flow. The problem is that the evaporator cannot keep up with the air flow across it, so the temp starts to rise.
To do it properly, if you increase air flow across the evaporator, you have to increase the evaporator capacity. Steve "a Porsche does more then just go fast in a straight line"
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SteveKJR Proud Owner of a 78 911 SC Targa "A Porsche does more then just go fast in a straight line" |
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Re: increasing cfm
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I have heard of people putting a newer model (87-89 I believe) fan assy in their car for more airflow. Not sure and you might want to do a search of Pelican on this. JoeA
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2021 Subaru Legacy, 2002 Dodge Ram 2500 Cummins (the workhorse), 1992 Jaguar XJ S-3 V-12 VDP (one of only 100 examples made), 1969 Jaguar XJ (been in the family since new), 1985 911 Targa backdated to 1973 RS specs with a 3.6 shoehorned in the back, 1959 Austin Healey Sprite (former SCCA H-Prod), 1995 BMW R1100RSL, 1971 & '72 BMW R75/5 "Toaster," Ural Tourist w/sidecar, 1949 Aeronca Sedan / QB |
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mannnnny have tried to re-invent this wheel on the board. i think i've read about every possible strategy for improving 911 a/c and what it all seems to boil down to (lol)..is that a holistic approach is required..no one thing seems to give you much improvement. even with the most ideal components installed, it isn't up to par with modern systems..the system is just spread too much around the car for physics to do its job well.
ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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bigchillcar I disagree. My winter project has my AC almost perfect the only thing I want to improve is the air volume. If I can get 10-15% more airflow it would be almost perfect.I have a Kuehl center vent that along with the center dash vents on my 83SC give plenty of volume, I just have to get more volume out of the side vents and I may bite the bullet and buy the Kuehl side vents. I am also going down the path of adding a small fan to the AC manifold that feeds the side vents to increase the volume.
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2002 Boxster S . Arctic silver + black top/int. Jake Raby 3.6 SS engine " the beast ". GT3 front bumper, GT3 side skirts and GT3 TEK rear diffuser. 1999 996 C4 coupe black/grey with FSI 3.8 engine . Rear diffuser , front spoiler lip with ducktail spoiler . |
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a front-engined, water-cooled car has all the advantages over our rear-engined, air-cooled cars. we need over 20 feet of hose to pipe our freon around to all the necessary components to finally get the cooled air to where we are up front in the car. air-cooled cars can get darned hot..we need aux coolers with fans in traffic conditions..our condensers need them too..these fans are a must if you drive in traffic. most of our cars have old, non-barrier style hose, so our systems need charging often. our evaporator/blower combo isn't as powerful as contemporary cars..some still use old piston compressors..modern condensers are more efficient. give it some thought and you realize that most of us need several upgrade mods to get anything close to comfortable in extreme heat. i'm all for hearing about ways to make it better..our a/c systems were engineered at the time as best as they could be owing to the disadvatageous nature of the design of the car. a/c is possible of course, just much more of a challenge in the design of the 911.
ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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First check for a clogged evaporator. Do you have a picture of the evaporator/blower unit? The knee pads vents help a lot into the a/c cooling into the cabin. My car have one of those vents system that you are talking about.
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1972 911T 1991 Mazda RX-7 Turbo II Are you car loosing power? When was last time you service your fuel injectors? Dirty fuel injectors? Why no try a complete fuel injector cleaning service and return the dignity to you car. Visit www.rennsportfuel.com and we will return your injectors back to life! |
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Join Date: Jun 2005
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Any know Evap fan CFM spec?
Does anyone know what the OEM spec is for CFM on the pre-'86 evap. fan. It is a Behr unit. There's a Red Dot "booster" that is rated at 230 CFM... could this be used as a booster to the existing evap fan or as a replacement?
Thanks...
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'79 911 SC |
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Re: Any know Evap fan CFM spec?
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being a christian, my recommendation for improving this is prayer..lots of it..
![]() ryan
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To the memory of Warren Hall (Early S Man), 1950 - 2008 www.friendsofwarren.com 1990 964 C4 Cabriolet (current) 1974 911 2.7 Coupe w/sunroof 9114102267 (sold) 1974 914 2.0 (sold) |
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BigChill... you're probably right, butt I was hoping to get a little older before I got totally cynical! Thanks....
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'79 911 SC |
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