DIY vac advance w/spring -- SUCCESS! (long) - Saab Performance Bulletin Board - Saabnet.com


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DIY vac advance w/spring -- SUCCESS! (long)
Posted by Notnoel [Email] (#23) [Profile/Gallery] (more from Notnoel) on Sat, 23 Dec 2006 09:56:36
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Thanks to Jak, MS, and 900 aero! Just installed my modded capsule and it works like a charm! I drilled out the stop and modified it as described elsewhere. Then drilled a hole in the top and bottom of the mount to attach a small rod parallel to the capsule (to attach one end of the springs to). I then drilled another small hole in the actuator to attach the other end of the spring to.

For the springs, I cannibalized an old 3.5" disk drive. These springs are stainless steel and about a 1/2" long and a 1/16" in diameter. They are pretty stiff and design to work under tension (to pop the disk out of the drive). I slipped my thumbnail into the spring and stretched out the end of the spring I planned to discard, cut off the excess, and bent the end into a hook. Next I attached the hook to the rod and the hole in the actuator arm so that the spring was under slight tension.

Next came bench testing using my boost gauge. Turns out one spring did not provide enough tension, so I added two in parallel. Under this set-up, the actuator began to move at about .2 bar and closed the stock gap at about .4 to .5 bar. I determined that the springs could only go on the underside of the actuator arm due to clearance issues. Since the modified gap of about 2 mm is twice the stock, it seemed like I was pretty close to where I wanted to be. So I modified the retard stop to an adjustable cam, set it for about 2 mm and tried my bench test. It hit the stop right at 1 bar, so I installed it in the car.

I set the timing at idle at 20 degrees, hooked up the gauge and vacuum hose and began incrementally pumping up the simulated boost. The timing retarded smoothly beginning at about .2 bar and landing at 10 degrees at 1 bar just as in the bench test. Nirvana on the test drive.

I don't seem to be boosting as far into the red as before, but I (still) haven't received my 3.0 bar FPR from the guy I bought it from on Ebay yet. I suspect that I need more fuel to compensate for the extra retard I've got now. I'm going to wait until that comes to fool around with really dialing this in.

I can't figure out how to post a photograph, so I'm going to email it to Jak since I can get his email address from his website. Thanks again to all of you for your help. This site (and you guys) rock!


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