Doing an APC upgrade yourself [Archive] - SaabCentral Forums

: Doing an APC upgrade yourself

23rd April 2002, 11:02 AM
Where do you get the supplies to do the upgrade? Who has done it on their cars?

23rd April 2002, 11:46 AM
Loads of people including me have tweaked their own APC's here. I got my resistors from Maplin, got fed up with buying the odd one every now and then (paying more for parking than the bits :roll: ) So I bought a school study pack, loads of bits in loads of boxes and a carry box for about 20.

In the US Radioshack should have them.

23rd April 2002, 01:02 PM
Yeah, as Keith says, lots of us have. It's very easy and cheap to do and gives a big boost in performance relatively safely.

Yes, Radioshack is the best place (although in my experience they sometimes have a limited range of resistors). Alternatively, for the real cheapskate option if you can read resistors (it takes five minutes to learn how to read them) then find an old broken radio/TV/telephone etc and pull out the resistors you need. That's what I did with the APC that Pete Tandino has used!


23rd April 2002, 02:45 PM
Theres a post some where on this board explaining how to read them. Alternatively, cheat and use a multimeter!!

23rd April 2002, 09:48 PM
Thanks a lot guys...I really appreciate the help!!

23rd April 2002, 10:06 PM
good ques though how to read the pots when adjusting them i really haven't a clue?

23rd April 2002, 10:12 PM
Well hear pretty soon I am gonna rip in to the apc and I will probably be coming back on here and ask questions hahaha. Thank god you guys are here

23rd April 2002, 11:25 PM
don't forget that you need more fuel at higher boost levels . i'm running 30 lb fuel injectors (red top) and a adjustable regulator (raises pressure 1 lb per 1 " boost)


24th April 2002, 08:05 AM
Really? On the Swedish Dynamics site they say nothing about needing more fuel at higher boosts. Please explain

24th April 2002, 08:37 AM
Just squeezing more air into the cylinders won't give you more power with a petrol engine. You need to keep the air to fuel ratio correct. So if you add more air you should add more fuel to keep the mixture correct & get more power! For Lucas injection a 3.0 bar fuel pressure regulator is enough to support a reasonable APC tweak but a better option is a Rising Rate Fuel Pressure Regulator (RRFPR) this raises fuel pressure at a rate proportional to boost pressure. The rate is what is quoted for the regulator.

So a 1:1.7 rated RRFPR would raise Fuel pressure by 1.7 psi for every 1 psi of boost.

<font size=-1>[ This Message was edited by: Keith on Apr 24, 2002 1:39pm ]</font>

24th April 2002, 09:49 AM
hmmmmm, alright that definately makes sense thank you

Carl Hernandez
24th April 2002, 03:40 PM
What about the earlier 900T's that sported the Bosch CIS system?
How would you go about as far as injectors and the pressure regulator?
From what it looks like the injectors are not electronicly controled.
I could be wrong.

Janne Selinummi
24th April 2002, 04:23 PM
The 8V Turbo has a Bosch K-Jetronic system, and that is a mechanical system. CIS means continuous injection system, and the injectors indeed aren't electrically controlled.

You can increase fuel feed by setting up a pressure switch that operates the cold start injector above certain boost pressure.
Set the switch to start extra injection at about 85 percent of your max. boost, and you should get noticeably better performance in high boost running.

FPR doesn't need to be changed, usually.
Also the fuel pump is well up to the job even with two extra injectors, like some have done...

Carl Hernandez
24th April 2002, 06:02 PM
Where would a good place to tap off the boost pressure be?
Are you talking about using a hobbs switch?

25th April 2002, 04:13 PM
how do you measure the pots on the apc circuit board or has noone done have they all bought theirs?

25th April 2002, 06:30 PM
1) Get a digital multi-meter.
2) Set it to a sensible range.
3) Stick the probes on the legs of the pots.
4) Read the display.

25th April 2002, 08:19 PM
Carl, you could use the overboost pressure cut off switch for this, it is already plumbed in and is adjustable.

Otherwise any of the rubber hoses attached to the inlet manifold are under boost when the turbo is blowing.