I wanted to post this modification last month but I got bogged down with the holidays and gigs. Anyway, I have been suffering thru the better part of the Porsche season with an Aux Air Regulator that I felt was closing to soon and dropping my warm up idle speed a bit too low. I had planned to just replace it with a new unit but at the current weak dollar price of $675 I decided I would modify what I had or return to a more elegant solution..the manual hand throttle! There are two forces that you are dealing with. The opening size, the larger the opening the faster the idle [ask me how I know] and the heating element that determines the rate of closing the orifice. My AAR had a heating element resistance of 17 ohms and took only 2 mins to close completely. I had read that 33 or so was what it should be. It made sense..higher resistance longer heat up time = longer time before closing. Once I was able to buy and install a spare used unit off of ebay [ from a turbo and good for an additional 20 hp ] it was time to dig into the little beast. First I marked the disc in its partially open position to serve as a reference. Then, I took the unit apart by drilling out the four rivets. See pics 1 and 2
Once I had it apart I began to understand how the thig worked..think Lionel Trains! So I dug deeper. I removed the large plug on the side of the unit to gain access to the nut that held the element in place. I used a C - Clamp to press the plug into the cavity for removal rather then drill it out and then be force to fabricate a new one. Once it was clear of the aluminum housing I had to nudge it over the the nut to get it to come out. Once you get into this it will make more sense.
I was then able to remove the 10mm nut and free the heating element from the housing. You will need to slide the spring metal wire retainer out of the housing so that you will have enough slack in the wire. It is the large square black object at the center foreground of the next picture. Also notice how I tapered the inside base of the large plug to make it easier to remove the next time. Don't go crazy the plug needs to seal when its re-installed.
When I saw the hand wrapped wire on the element I knew the AAR could be modified. I went online and searched for resistance wire and found a company in Naples, Florida that would sell short lengths. The Company is called ..dig this...Pelican Wire Company !
http://www.pelicanwire.com
From the resistance measurements that I had and the existing wire diameter I determined I needed 30 gauge Nichrome 80 wire with double glass, silicon insulation. This wire had a resistance of 6.48 ohms /foot and sold for $20 for 25 feet. Once my order arrived I started on the rewiring of the element. I unwraped the old wire and cleaned the sleave and applied a small amount of insulating varnish to help tack down the wire.
Then I measured out about 6 feet of the new wire and measured the resistance. Which came out to 38 ohms. I wrapped the wire neatly and tightly around the sleave for a nice even layer [ while the varnish was still tacky]and then started a second layer until I had used up the length. I let it dry.
I re-installed the heating element and then replaced the extra insulation on the wire ends and soldered them to the connector.
While the large plug is still out of the housing you can adjust the position of the heating element and its relationship to the opening. This is where my marks came in handy.
I buttoned the AAR back up and tested it before I installed it. With the reduced opening size it still took the AAR 5.5 mins to close completely! Installed on the car I'm getting cold start idle of about 1250/1300 rpms for the first 40 seconds or so then it drops to around 1K /900 until the engine warms up [past the first tick on oil temp gauge]. Best of all no more stalling!
So far so good. YMMV
Peace, Ron
www.mysterytrain.org