Date: Mon, 04 Jan 1999 10:42:27 GMT From: supersambanopsamejanews.com Subject: Re: more HP- free!!!!!!!!!!1
In article <368F4FF2.75A7E0D5nopsamsouth.net>, Riff <turbospgnopsamsouth.net> wrote: > from stefan bolin- > Tweaking the control unit! > > Extreme caution should be taken when adjusting the control unit since > there are three adjustment. If you adjust the wrong one, you might as > well > throw the control unit away since the chances of getting it back to the > original setting is practically impossible. If you feel brave, dig in, > it's not > difficult. > True it is not difficult but if you manage to go to far or by-pass the APC you will run the risk of hitting the over-boost switch. This has happened to me a couple of times and is diffenetly worth avoiding. > First you'll have to take the four screws out of the top of the box. > Remove the top cover > from the box. You will see three holes in the top circuit board that > gain you access to > the three adjustments inside the box. Actually all you have to do is remove the SAAB security tag from the side of the box. Then just lift of the plastic strip that goes across the top and hey presto! 3 little holes in the top of the box marked P F K. I have found it easier though to take the box apart since the pots are tiny and require a carefull hand. >Some of the earlier control units > have the > adjustment screws obviously marked with the letters K, F, and P (Knock, > Frequency, > and maximum boost Pressure). If you don't have one of the earlier units, > you'll have to > look a little deeper to find the markings. Some units may not be marked > at all. On my > control unit, the screw on the right was marked with the letter P. I > turned the screw 1/4 > turn clockwise and test drove the car. There was a modest increase in > boost pressure. > I turned the screw another 1/4 turn clockwise and test drove again. > Again a bit more > boost. Finally, I turned the screw about 1/16 of a turn all the way to > it's limit. This gave > me about what I was looking for. The boost went right to the end of the > gauge. This is > about 14-15 psi. > Are you sure about this 15 psi on my car 84 900T16 UK is about 1 cm into the red. The cut-off switch is just over half way into the red. STANDARD boost is at the end of the yellow. It even states this in the original owners manual. > To get rid of the boost taper, you'll have to consult one of the major > Saab tuners and > ask them about their modified control units. A red box is I guess the best answer. However you can also try turning the F pot about 1/4 turn as well. This pot is supposed to adjust the duration of the boost. > If that's not enough boost pressure for you, try jumpering the wires for > the pressure > transducer so that the APC control unit doesn't know what the boost > pressure is and > will rely solely on knock. I tried this on my car and did not like the > results, however, > several people who I know run their APC systems this way and have > experienced no ill > effects. I am very surprised people would want to drive like this. The results are basically a waste of time since the APC unit seems to have a built in safety backup just in case this happens (i.e because of a pressure transducer failure or droped pressure line). I tried this by wiring a 10 ohm resistor in place of the pressure transducer. What happens is that you get a gut wrenching wall of torque as soon as the boost comes on just below 3000 revs. This is then pissed away by the APC at around 3500 to 4000 revs back down to base boost. This is not only anoying but dangerous if it happens when over taking a truck for instance. You either put up with the APC or dump it completely. Personally I am quite happy with it since it gives the SAAB the kind of driveability laking in other turbo cars. > One certain '86 Saab 900 turbo is running up to 20 psi with > the transducer > jumpered and a boost enrichment system. > > For those of you with Garrett T-03 turbos, 16-17 psi is about where the > efficiency of the turbo goes away and the air coming out begins to get > really hot, so running the system with the pressure transducer may be > advisable. > > Another thought... > > Another thought I have had is to bleed off the pressure to the > transducer with a small bleed-off orifice to let the boost pressure get > up to about 17 > psi. You'll have to experiment with this idea. > > Putting a resistor in series to the transducer won't work because as the > pressure goes up, the resistance goes down. You could possibly install > a variable resistor in parallel with the transducer though. Just wire in a largish resistor in parrallel with the transducer. The combined resistance is simply 1/R = (1/r1) + (1/r2). Again though I have found this doesn't really do anything since all you are doing is reducing the effective resistance read at the APC as the transducer ramps up (i.e. no real gain in boost). Really the only thing to do is to adjust things on the control board itself. Using a bleed of orifice is going to be incredibly difficult to implement acurrately, however you may be able to do it with a clamp on a small rubber tube. Adjusting the clamp should give you the right size hole -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
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