Can you increase A/C Blower Output & where to buy knee pad vents?

[Rodney Nelson]

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.

[jtratza]

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.

[kuehl]

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!

[Rodney Nelson]

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.

[stormcrow]

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"

[scottb]

Originally posted by kuehl
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.

Along with Charlie, the folks at Performance Aire are among the most knowledgeable in the country when it comes to 911 a/c. It's worth a call to see if they're the West Coast outlet Charlie's referring to.

[Joeaksa]

Originally posted by Rodney Nelson
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.

Performance Aire had these vents. I have them on my car and they work well. The link above takes you to their main site, then go to the Performance Aire icon and have fun. They are very helpful and nice to work with.

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

[bigchillcar]

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

[rfuerst911sc]

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.

[bigchillcar]

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

[Nitrometano]

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.

[Border911Dude]

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...

[scottb]

Originally posted by Border911Dude
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...

Intriguing idea. Have you found a place to mount it?

[bigchillcar]

being a christian, my recommendation for improving this is prayer..lots of it..
ryan

[Border911Dude]

BigChill... you're probably right, butt I was hoping to get a little older before I got totally cynical! Thanks....