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Re: SPG Performance & APC and Turbo Boost
Posted by Jouko Kuisma (more from Jouko Kuisma) on Thu, 18 Nov 1999 09:41:32
In Reply to: , Kok Chen, Sat, 17 Dec 1988 12:00:00 

>would replace every single one of them w/ 100% silicone lines. As far
>as a tweaked APC box that was done by a someone w/ nothing more than
>a screw driver there would be no way I would trust putting it in use
>w/ my car. If you want a reprogrammed APC to deliver more boost then

I completely agree with You, Todd. Personally I find it very depressing to
read the APC tweak instructions on the Saabnet BB's, for example. One with
a car as technically advanced, reliable and expensive as a Saab turbo with
APC should realize that the APC box isn't there just to restrict the power.
Beeing an advanced knock detector, there's nothing worse you can do to your
APC than to adjust the frequency potentiometer without reference values,
for example. The advices like 'turn it 1/4 round clockwise' may sound
fairly simple, but one should realize that just a small play in the pot
makes a big difference in real life when it comes to knock detection.

There are MANY suppliers out there with adequate experience and reference
values for tweaking the box. Of course, if you're willing to experiment and
take the risk of totalling the engine, why not? Turning the pressure pot A
LITTLE may not hurt, but... For the rest of us, intending to keep our daily
drivers in shape, I'd recommend shopping for the upgrade. Here in Europe
I've done business with BSR of Sweden. For about $190 they calibrate the
box and add an external pot you can attach to the instrument panel for easy
pressure adjustment.

I've been very happy with the moderate upgrades I've made. At the moment I
am, however, puzzled with the problem I'm having with knock detection. The
APC has been tweaked to give a maximum of 20 PSI (recommended max. 17,5
PSI), but in real life the APC limits the pressure to about 15 PSI. There's
obviously something causing knock (no, turning down the APC knock
sensitivity surely ISN'T the way to go!), but the reason remains a mystery.
We just did a dyno drive and it showed that there's no problem with the
fuel supply (3bar FPR), and everything else seems to be fine as well
(measured at a dyno with premium fuel and large fans in front of the car,
plugs OK, ignition timing is ok (standard), open-cone filter with access to
cold air flow, intercooler fan). Any ideas where to look next? I HAVEN'T
cleaned the throttle body, cooler or pipings yet.

For your information: With charging pressure at 15PSI, this Saab900T16
(1990) measured 207bhp no39sdcx6spamx782 5700 rpm and 230 lf-ft no39sdcx6spamx782 3000rpm. According to BSR
the realistic max with 17PSI and standard turbo is about 230bhp.

Jouko Kuisma
Espoo, Fin

Posts in this Thread:
StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
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