| Here are a few pictures of removing the apc box and adjusting the settings. Note: Changing the 'K' setting is not recommended! The 'K' setting affects the sensing of engine knocking which reduces the boost to protect the engine. Since most of us aren't calibrating this on a bench with test equipment we should leave the "k" alone. |
| Since you get more power by adjusting these settings, I assume your drivetrain lifespan might be reduced. I don't have proof but it seems logical. |
| Here's where the apc box is located on Saab 900 turbos after 1985. I believe all 1985 and earlier are under the rear seat. |
| Here's the two screws that hold the apc mounting bracket to the fender. |
| Notice how the connector has to fold out, then the other end unhooks. |
| Here is one of the four phillips head screws that hold the top half of the apc box on. Don't set it on the engine or fusebox while taking these out since one might drop into the engine bay. I found that out the hard way! |
| The top cover slides off. Notice you don't have to remove the circuit cards from the lower box to adjust the potentiometers, (pots). |
|
Here are the adjustment pots. 'F' and 'P'. 'P' and 'F' are related. Other than that I can only tell you what I did. For a full description of APC theory take a look at
Kevin's APC Theory.
A long time ago I turned 'P' cw from 4 o'clock to 8 o'clock. Then recently I turned my 'F' clockwise from 5 o'clock to 9 o'clock. But I backed the 'P' down ccw from 8 o'clock to 6 o'clock after being advised by Kevin. Now it runs great! |
| The pots are actually located on the bottom card. You go through the holes in the top card to adjust them. |
| Here I'm adjusting the 'F'. Be careful since these pots are fairly fragile and they DONT turn a full 360 degrees. It would be worth buying the proper sized screwdriver if you don't have one. |
| Here's the fuel pump cutout switch on cars up to '88. Last I heard turning the center screw 1.5 turns clockwise will raise the cutout limit to around 18 psi. The switch is set from the factory to cut the fuel pump at 14.7 psi. The switch is located on the drivers side dash area behind the panel right about at your left knee. I disabled mine since it leaked air. |
|
Here's the boost pressure transducer. It has a turbo air pressure line input and converts the air pressure to electrical resistance. This is what apc uses to determine the boost level.
You can make adjustments to the 'F' and 'P' and take a test drive. If you aren't happy it only takes about 10 minutes to remove the apc box and make another adjustment. Update: I figured out that you don't even need to remove the entire apc box. You can remove the top cover and adjust the pots with a small, short screwdriver. I recently bought spg9.com's apc box. I took a peek inside to find several component changes and other modifications. For that reason, it controls boost better than tweaking the stock box ever could! |