Date: 3 Nov 1997 04:56:03 GMT
From: "petrol" <>
Subject: APC Adjustment Info

I have an 87 900 turbo, with 102k on the odo. I have gathered FAQ's, talked with other techs, read schematics, and everything else I could to try and unravel some of the unmentionables behind the SAAB APC system. I have made the following mods to mine and there is a major increase in safe horsepower. I take no "full" credit for this content, it was gained from a multitude of sources. The APC box on 900turbos after 86 ( I believe the year is right ) is under the bonnet on the drivers side fender. It is under the rear passengers arse on 85 and back models. Under the bonnet you will notice a black box that is about an inch and a half thick, 5 or 6 inches wide, and about 5 inches long. It has a large connector on the botttom side of it. There are 4 silver phillips screws that hold the top portion of the cover on. If you remove these screws, you can remove the top cover of the box, revealing a 2 tiered circuit board. If you lean over the engine and look at the engine side of the circuit board, you will notice 3 holes in this board marked P, F, and K these are identified as such, P being boost pressure levels, F being the "time" that maximum boost is sustained at open throttle, and K being a sensitivity adjustment for the Knock sensory circuit. You can see that these holes allow access to the potentiometers on the fender side circuit board. These "pots" are adjustable with a very small flat-head screwdriver. Here is what I did to tweak mine into pure bliss... I drove the car for about 20 minutes to make sure it was already at optimum temperature level. I found a nice open stretch of road, with minimal or no traffic around. I adjusted the "P" pot up a hair, and drove the car at full throttle in top gear and watched the boost. This will take several passes to get adjusted properly and get it right. Mine stops right at the "redline" for the boost gauge, witch is still safe for the engine. When you make these adjustments, the increments must be VERY small. The pot's only turn about 1.5 turns for the full range so if you make a quarter turn on 1 run, you are overdoing it! After you have adjusted the P pot to a desirable level, than adjust the F pot all the way out... This will allow you to sustain that boost as long as you keep that foot planted into the floor. Otherwise it will gradually fade back down to about 1/4 boost. I havent messed with the K pot at all simply because I use 93 pump octane and even add an octane booster sometimes, so knock is very rare in my case. Please let me know any success stories or other info that you recieve or experience on this matter and I will keep compiling info to better inform SAAB enthusiasts such as ourselves. I have done a great deal of research on SAAB turbocharging and am in the process of a major upgrade of the turbo unit and intercooler, for less than the cost of the stock unit. I can also get very, very good performance reman turbosystems for Saabs for a lot less than the factory unit from the dealer, and they have impecable warrantees... Please keep in touch, Petrol, Dallas TX

Return to Main Index

The content on this site may not be republished without permission. Copyright © 1988-2020 - The Saab Network -
For usage guidelines, see the Mission and Purpose Page.
[Contact | Site Map | on Facebook | on Twitter | Shop Amazon via TSN | Site Donations]