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Saab APC: Modifying and Installing

What are the advantages of a red box?
Red Box APCs were fitted to the last two years of SPGs (90-91), as well as the Commemorative Editions that followed. Additionally, prior to that, you could buy a red box APC out of the Accessories Catalog; depending on the year, it came with a slightly higher pressure fuel regulator (by 0.3 bar), as well as a distributor with a better boost retard curve.

Stock, run-of-the-mill 900 Turbos made 160 hp/188 ft-lb, while the hottest, latest (90+) red boxes made 185 hp/low 200s ft-lb. The standard, 160 hp version allows about 11 psi (assuming high enough octane) max boost. If you fit one of these APCs to your Volvo, and you are not running more than 11 psi, then it makes no sense to modify the APC to "red box specs" (e.g., the "recipe" at 900aero.com). A nice thing for 900T owners is the ability to add 25 hp for the cost of a few resistors, a used fuel regulator from a non-turbo car, and a minor mod to the distributor vac capsule, all for $10 or so.

Your "base boost" (wastegate opening pressure without APC hooked up) should be half of max boost. If you always run good gas, then you can bump that up a couple psi.
 
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mbc can still be used right? or do you turn up the boost via the APC? I just got a redbox and want to hook it up tomorrow, just curious if the mbc goes inbetween the compressor and the 3way or the 3way and the WG?

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nevermind...reading on the saab forum i found that this is dumb....boost can be turned up via the "f" pot on the apc
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ok, bump!
there is a 1988/1987 Saab 9000 turbo in the junkyard, already grabbed the solenoid and pressure sensor, but i cant find the APC box itself. I removed both the kick panels on the driver and passenger side and looked in the engine bay and under the windshield cowl stuff, the box is nowhere to be found. The car was basically untouched when i started dismantling it, i doubt that the box is gone (no traces of removal...). Where is the APC box..? I thought it was near the driver side dash.
 
Its bolted to the drivers underdash bolster. You have to remove it to unscrew it from the panel, or remove all the torx and pull it out the back.
 
Last month i got a complete APC setup. Thanks Chad, Ruben!

Time to bump this thread with some extra info.
I did some research (ctrl-c ctrl-v, cough) and there are a few (useful) functions that could be nice to add to a install.

This is the unofficial connection diagram of the 25-pin APC.

Pin 1: not conncted
Pin 2: not conncted
Pin 3: not conncted
Pin 4: knock sensor shielding
Pin 5: GND
Pin 6: not conncted
Pin 7: not conncted
Pin 8: not conncted
Pin 9: not conncted
Pin 10: Pressuresensor in
Pin 11: some kind of test output for the F-circuit
Pin 12: solenoid out
Pin 13: +12v
Pin 14: not conncted
Pin 15: not conncted
Pin 16:knock sensor in 1
Pin 17:knock sensor in 2
Pin 18: internal knock signal. Grounding this signal will disable knock circuit. Applying voltage will trigger knock circuit (lowering boost)
Pin 19: Knock indicator out ("lowers" to GND when knock occurs). You should use a LED for this. No need to add a resistor in line.
Pin 20: brake signal in (+12v). Disables APC but Knock light etc stay active afaik. Ground this pin and boost is regulated by wastegate setting (spring) only. Nice when you need to lend your car to someone else. Fun-killer-switch.
Pin 21: not conncted
Pin 22: same as pin 20
Pin 23: Pressuresensor in 2 (GND)
Pin 24: F-circuit indicator out "lowers" to GND when F-circuit is enabled. is connected the same way as pin 19. It will blink once when F is reached and flash continuously when F is regulating top boost.
Pin 25: RPM in

This "unofficial" wiring diagram includes the test inputs and outputs used to test and calibrate the APC when manufactured. You should not connect anything to the test-pins if you are not sure what you are doing! Info by Anders Olsson.

On 900aero.com you can find a few excellent articles on APC function/troubleshooting, tuning, modifying and simulation. (links are directly to article, may cause issues, otherwise Home>tech info)
There is really a lot of stuff built into the APC, for example it hears engine noise (not knock) with the knock sensor, when that noise isn't present, no extra boost.

Info by Anders Olsson.

The connectors inside the APC plug are the same as found in Volvo LH/EZK plugs and on DIN radio connections.

Have fun with the APC. Mine should be going in this summer.
 
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Last month i got a complete APC setup. Thanks Chad, Ruben!

Time to bump this thread with some extra info.

I also just scooped a complete APC setup and should have in a week of so. Time to read the articles.
 
bump , seems like i need this, sold my boostcontroller out of confidence this is way cooler .. now to find one :lol:
 
all the years of the 9000 with turbo have the unit?


No. '93-'98 def. would not have it, and I believe '90-'92 with direct ignition did not have it. '86-'89 should definitely have it, as well as full pressure turbo (boost gauge in the cluster) 16v c900s. (my '91 fpt 900 has an apc box)

This is what I know for US cars, though...there may be differences in other countries...
 
I'm starting to think about wiring mine up. It seems to me that most all the wires needed for the APC can be found on the ICU. (12V, GND, knock sensor and possibly RPM) The rpm signal is pre power stage so that's why I said possibly. Any thoughts on mounting it close to the ICU and running short wires over to pick up most of the wiring. obviously I don't want to add any potential problems for the ICU and would add an inline fuse to the 12V.
 
Someone was going to get me a complete APC setup but that did not take place. That said, I was able to slowly pick up (hopefully) all the parts. I am going to run my own wires.

yama, I myself thought on using op-amps when I such the signal off the knock sensor. May do the same for rpm as needed; I can always then make it spit out whatever voltage range I want. :-D

Your idea to suck the signals out for the (or before) ICU is not bad at all. Now I am thinking... something scary to all involved or nearby. :omg:
 
I modified my APC, it should be able to adjust boost from 0.5-1.5 bar without the boost lowering at higher rpm. You set a boost and when it hears knock (above 2300 rpm) it will lower boost till the knock is gone.
You basically set it at a certain boost level (together with the wastegate pretension, it needs to open at roughly 50% of the boost that is set in the APC, eg, wastegate at 7-8 PSI, adjusted boost in APC ~15-20 PSI).

Still need to install my APC, so this bit is just theory (the way I understand the APC), not tested yet.
 
I've installed my APC this weekend. You can set the max boost level on the APC circuit with the F potentiometer.
(Some boards, such as mine, do not label the potentiometers. They are the blue square looking pieces from left to right, P, F, K. P and F being close, K being farther away.)

The APC will keep increasing the boost until knock occurs and then decrease in 1.5PSI increments until the knock is gone. It seems to me that the preset level is ~13PSI, I have read some folks say that 13PSI is simply all the 13C is capable of. However, when adjusting my MBC, I seen numbers quite a bit higher than 13PSI.
 
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