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If anyone remembers my past post on this topic, I had told about the incredible difference in power when removing Fuse 9, which controls Pin 14 that tells the ECU the car is an auto. I did this on one trip into work one morning. The ECU will follow a path of pre-determined performance levels based upon what transmission is installed. Certain parameters are lowered (torque, hp, boost) in an auto. The consensus of this board as to the reason that the ECU does that is to protect the autobox, but even Saab never officially states that that's the reason it's done. I've asked different dealerships' service mgr's, as well as Saab Performance Group here in CT, and no one actually knows the real reason. In fact, the SPG advisors even stated that they constantly upgrade auto-equipped Saab 9K's to very high levels and never have a problem with the transmissions spontaneously combusting.
In any event, I have done further testing with this trick. For the last two weeks, I have removed Fuse 9 before start-up (since that is when the ECU decides what performance path to take), and re-inserted it after the car is running. According to a past post, this fuse also controls some very important components (brakes, for example, as well as my radar detector), so best to put it back in.
Findings: car is transformed into a pavement-eating, tire-burning, stealth-flying machine. I am not joking. Granted, I have a Stage 3 set-up (ECU, exhaust, air delivery, BPV), but I'm sure even in stock form the car will feel tremendously better. Normally, boost averages around 16 psi. With fuse 9 removed, boost is consistently at 20 psi. Touching the gas pedal results in quicker throttle response. The engine also idles more smoothly than when fuse 9 is left in at start-up ("autobox mode"). I've noticed the ECU has adapted to a higher-performance level, since on the trips I allow the ECU to remain in autobox-mode, the car has become quicker. I've been doing most of this test while manually shifting the tranny (which is becoming the normal way of driving this car for me now, esp. since my other Saab is a stick), but even when I punch it hard and allow the tranny to shift by itself, it's always a smooth shift.
I will definitely look to installing an in-line switch to Pin 14 since this is the way to go. Removing fuse 9 is a bit of a hassle, so to flick a switch seems ideal.
Question: does anyone know where Pin 14 goes to (the other end)? Rather than splice into the wire, I'm wondering if I could just disconnect the wire at the non-ECU end. Yes, I could do it at the ECU end (as was previously explained in a past post), but that would mean having to disconnect the ECU itself, and I really do not want to mess up the adaptation it's currently at (way too much fun...).
Joe
'98 77K
'93 900TC 129K
posted by 12.111.48...
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